Early Development and Parenting, Vol. 4 (4), 191-207 (1995)
Co-Morbidity of Crying and Feeding
Problems with Sleeping Problems in
Infancy: Concurrent and Predictive
Associations
Dieter Wolke
Renate Meyer
Barbara Ohrt
Klaus Riegel
University of Munich, Germany
The co-morbidity of crying, feeding and sleeping problems at 5
months of age was investigated in a representative sample of 432
infants in South Germany. A crying, sleeping or feeding problem
was reported in 32.7% of these infants by their parents and a
further 14.6% had two or more of these problems. Little comorbidity between crying and feeding problems was found. There
were moderate to strong associations between crying and sleeping
behaviours. Feeding problems showed little relationship to
sleeping behaviour, but feeding type and frequency of feeds
were related to night waking. Breastfed infants woke much more
often at night. Crying and feeding problems at 5 months were poor
predictors of sleeping behaviour at 20 or 56 months of age. Later
sleeping behaviour was best predicted by infant sleeping
behaviour. At 56 months, maternal distress due to sleeping and
co-sleeping practices was predicted by maternal distress due to
crying and feeding practices at 5 months of age. The predictions
were significant but generally weak to modest in strength. Future
studies on the consequences of crying or feeding problems should
take into account patterns of co-morbidity. So-called 'post-colicky'
sleep problems are not due to increased crying per se but rather
appear to be the consequence of associated infant sleeping
problems and parental caretaking patterns for dealing with night
waking in infancy.
Keywords: co-morbidity; colic; sleep problems; feeding; stability;
continuity.
The belief that crying, feeding and sleeping
behaviours are related in infancy is held by both
Address for correspondence: Dieter Wolke, University of
Hertfordshire, Psychology Division, College Lane, Hatfield,
Herts, AL10 9AB. email: D.F.H.WOLICE@herts.ac.uk,
CCC 1057-3593/95/040191-17
©1995 by John Wiley & Sons, Ltd. parents and physicians (Oberlander et al., 1992).
This belief is most prominent when the infant is
seen as suffering from colic or night waking
problems (Wolke, 1994a). Changes from breast- to
bottle feeding, frequent changes of formula feeds or
the introduction of cereals or solids as remedies for
Received 12 January 1995
Accepted 14 August 1995
192
both night waking and colic are often applied by
parents with or without the advice of their
physician (Beal, 1969; Oberlander et al., 1992
Forsyth et al., 1985a; Keane et al., 1988; Macknin et
al., 1989; Hide and Guyer, 1982; Loughlin et al.,
1985). These practices testify to the strength of the
belief that crying, sleeping and feeding are interrelated.
This popular concept is also reflected in recent
contentions that infants characterized by hyperarousability and difficulties in self-soothing (excessive crying), sleeping or feeding should be
considered as regulatory disordered (Greenspan
and Lourie, 1981; DeGangi et al., 1991). DeGangi et
al. (1991) proposed that infants who manifested
two of these four characteristics should be considered to have the diagnosis 'regulatory disordered infant'. This diagnosis thus presumes
significant co-morbidity of crying, sleeping or
feeding problems.
However, it is not clear that these beliefs and
assumptions are supported by empirical evidence.
Is there empirical support that concurrent crying,
sleeping and feeding behaviours are interrelated?
How many infants have feeding or sleeping
problems in addition to excessive crying? Is there
evidence that multiple problems have stronger
associations with later regulation problems such
as sleep difficulties than single problems of crying,
sleeping or feeding?
The available evidence is more diverse and
sparse than the folklore belief might suggest. There
are numerous studies concerning normative developmental patterns of crying (e.g. Barr, 1990a; St
James-Roberts and Halil, 1991), sleeping (e.g.
Anders and Keener, 1985; Bamford et al., 1990;
Parmalee et al., 1964) and feeding behaviours (e.g.
Lindberg, 1994; Skuse and Wolke, 1992; Wolke,
1994a) considered by themselves. Some have
reported patterns of development in two or all
three of these behaviours (e.g. Forsyth et al., 1985b;
Jenkins et al., 1980; Klackenberg, 1971; Michelsson
et al., 1990; Lee, 1992, 1994) but have only cursorily
considered interrelationships among them. There
are also naturalistic or intervention studies of
infants with excessive crying (e.g. Wolke, 1993a;
Barr et a1., 1992), sleep problems (e.g. Johnson, 1991;
Jenkins et al., 1984; Rickert and Johnson, 1988) or
feeding problems (e.g. Wolke and Skuse, 1992;
Lindberg, 1994). Again, however, co-morbidity of
these problems has rarely been considered in these
studies (Wolke et al., 1994a).
Only the concurrent relationships between feeding and sleeping or crying behaviour have received
D. Wolke, R. Meyer, B. Ohrt and K. Riegel
much empirical scrutiny. Most of these studies
show that breastfed infants wake or feed more
frequently at night in the first year of life (e.g. Butte
et al., 1992; Wright, 1993; Eaton-Evans and Dugdale, 1988; Elias et al., 1986; Wailoo et al., 1990; Van
Tassel, 1985). Nutrition (e.g. sucrose) provided in a
single feed influences crying and sleeping behaviour and soothes the infant immediately after the
feed (Barr et al. 1994; Yogman and Zeisel, 1983;
Blass and Smith, 1992; Blass and Ciaramitaro, 1994;
Barr, 1994; Oberlander et al. 1992). There are a few
retrospective reports (e.g. Golding, 1986; Pollock,
1992) on the long-term effects of early feeding type
or nutrition on later sleeping or other behaviours,
but these relationships have not been studied
prospectively.
Very little is known about the relationship of
excessive crying and concurrent or later sleeping
and feeding behaviours. Weissbluth (1981), Hurry
et al. (1991) and Lee (1994) reported that concurrent
total sleep duration of infants who are temperamentally difficult or who cry excessively is
significantly shorter in comparison to 'easy infants'
or normative criers. Weissbluth et al. (1984a) further
reported that infants who had suffered colic in the
past were more likely to have shorter sleep
durations and more interrupted sleep (i.e. sleeping
problems) between 4 and 8 months of age.
Weissbluth (1987) interpreted these findings as
suggesting that congenital biological factors led
initially to colic and persisted for a period of time.
Others suggest that state regulation problems may
be maintained by the failure of the parents to
establish regular sleep patterns when the colic
dissipates, a problem of goodness of fit between
infant characteristics and parental caretaking
(Carey, 1989; Thomas and Chess, 1977).
To better understand interrelationships between
these early behaviours, a prospective community
study of a representative sample of infants in
South Germany is presented which addresses the
following questions: (1) Is there significant comorbidity between increased crying and sleeping
and feeding problems in infancy (at 5 months of
age)? (2) Do multiple problems mean more
distress for the parents? (3) Are increased levels
of crying or early feeding problems predictive of
more frequent sleeping problems in the preschool years (i.e. more than 1 and 4 years later)?
and (4) Do multiple regulation problems (i.e.
regulatory disorder) have a poorer prognosis for
later sleeping behaviour than single problems
such as increased crying or feeding problems per
se?
Co-Morbidity of Crying Problems
METHOD
Sample
The cohort consisted of all infants born alive in the
geographically defined region of South Bavaria
(N=70 600). Infants were enrolled in the Bavarian
Longitudinal Study (see Riegel et al., 1995; Wolke et
al., 1994b,c, 1995a,b; Wolke, 1993b) during the
193
•-
period from January 1, 1985 to March 31, 1986 and
who required admission within the first 10 days of
birth to one of the 19 children's hospitals or
paediatric specialist centres in this region (7505
index children, 10.6% of all births). In addition, 916
children receiving normal postnatal care were
enrolled as controls.
From this cohort, a normative randomly chosen
stratified sample was studied longitudinally which
Table 1. Definitions of crying, sleeping and feeding variables at 5 months
Crying
Cry duration
The continuous time variable was dichotomized as follows:
<2 hours/day of infant crying (intensive and continuous distress vocalizations)
>or=2 hours/day
Cry amount
Low to average according to maternal rating of crying per day
Above average
Soothability
Easy: mother rated the infant to be usually easy to soothe once crying
Difficult: mother rated the infant to be usually difficult to soothe
Cry distress
The mother was asked (a) about distress caused by crying currently; (b) distress caused previously (before 5 months).
Answers were combined to classify mothers as:
Never distressed: the mother never felt distressed by crying (neither previously nor currently).
Distressed:
(a) the mother felt distressed previously
(b) the mother felt distressed previously and currently
(c) the mother felt distressed only currently
Sleeping
Night waking
The infant woke on 5 or more nights per week
Long night-time awakenings
No/short: The infant did not wake at night or when awoken the arousal usually lasted for less than 15 minutes
Moderate/long:The infant woke at night usually for 15 minutes or more
Parental distress
The parent reported that s/he felt distressed by the infant's sleeping behaviour
Feeding
Feeding type
Breastfeeding: the infant was still (a) fully or (b) partially breastfed at 5 months
Bottle feeding: the infant had been (a) bottle fed since birth or (b) had been changed from breast-to full bottle feeding
before 5 months of age
Number of meals per day
Total time spend feeding (min)
Problems with drinking
The infant had regular problems with drinking fluids (most days per week) such as excessive drooling or problems
swallowing (either (a) previously or (b) still at 5 months)
Vomiting
The infant had brought up food regularly (most days per week) either (a) only previously or (b) still at 5 months of
age
Flatulence
The infant suffered regularly (most days per week) from flatulence either (a) only previously or (b) still at 5 months
Bowel (gastrointestinal) problems
The infant had recurrent diarrhoea or constipation either (a) previously or (b) still at 5 months
I.94
was representative of infants born in 1985 in
Bavaria (Bayerisches Landesamt fiir Statistik und
Datenverarbeitung, 1986; Bayerische Landesdrztekammer und Kassendrztliche Vereinigung Bayern,
1985) according to sex of child, size of community,
educational level of mother, gestation at birth and
hospital admission in the first 10 days of life (see for
details Riegel et al., 1995; Wolke et al., 1994b,c). The
final sample consisted of 432 infants and their
parents.
Procedures
Parents were approached within 48 hours of the
infant's hospital admission, the study aims were
explained and the parents were asked to give
written informed consent to participate. The
assessments of biological and sociodemographic
information have been described in detail elsewhere (Riegel et al., 1995; Wolke et al., 1994b,c,
1995a). Follow-up visits were scheduled at 5 and 20
months of age (corrected for prematurity) and at 56
months chronological age. As part of a neurodevelopmental assessment, parents received a
standardized interview from paediatricians of the
Bavarian Longitudinal Study Research Team
regarding crying, sleeping and feeding behaviours
and problems with these behaviours at 5 months.
The information obtained and the definitions of
crying, feeding and sleeping behaviours or problems are given in Table 1. In addition, parents
were asked whether these problems had been
present before 5 months of age. For example (see
Table 1), it was asked whether the mother was
distressed about crying at 5 months, and whether
she had been distressed about crying prior to 5
months. Thus, mothers could be considered to
never have been distressed about crying, distressed
only at 5 months or only before 5 months or
continuously distressed (before and at 5 months)
by infant crying. Information on current and prior
behaviour was also obtained for feeding type and
for problems with drinking, vomiting, flatulence
and gastrointestinal difficulties.
Sleep problems were also assessed during a
structured interview at 20 and 56 months of age
(for details Wolke, 1995; Wolke et al., 19941,, 1995a).
The information obtained included presence of
night waking (5 or more nights per week) at 20
months and 56 months. At 56 months, co-sleeping
practices of the parents (sleeping part of or all night
in the same bed with the infant), problems falling
asleep ((a) time until asleep >30 minutes or (b)
parents staying with child until asleep) and
13. Wolke, R. Meyer, B. Ohrt and K. Riegel
parental distress caused by the child's sleep
behaviour were elicited.
A distinction was drawn between caretaking
behaviours of the parents, infant behaviours which
are problems for parents and the impact of these
problems. Behaviours were feeding type, number
of meals, total time spent feeding and co-sleeping
(at 56 months). These differences in behaviour or
caretaking style are not usually considered as
problems leading to help-seeking by parents (Barr
and Elias, 1988; Wolke and Skuse, 1992; Lozoff et
al., 1984). Problems were those behaviours which
often led to complaints and help-seeking by
parents. These included long crying duration
(>2 hours/day), above-average crying amount
and difficult soothability for crying (St JamesRoberts and Halil, 1991; Wolke et al., 1994a); night
waking, long awakenings and difficulty falling
asleep (at 56 months) for sleeping (Messer, 1993;
Wolke, 1994b); and problems with drinking,
vomiting, flatulence and gastrointestinal disturbances for feeding (Lindberg, 1994). Distress
caused by crying or sleeping problems was
considered as measures of impact on parents (St
James-Roberts, 1992).
Statistical Analysis
Group comparisons of categorical data were
carried out using chi-square statistics with continuity correction or Fisher's exact test depending
on cell frequencies. The phi-coefficient was applied
as a measure of association (correlation) between
categorical variables. T-tests for independent samples were used for continuous variables and
multiple predictions of categorical and continuous
variables were computed using logistic regression
analysis. The p-value was set at p<0.05 (two-tailed
test).
The predictions as to future sleep behaviour were
always computed using the presence of behaviours
or problems prior to or at 5 months. If the
prediction of future sleep behaviour was different
when the behaviour or problem was present only
Table 2. Convergence of the four different cry
behaviour measures (phi-coefficients) 1
Cry amount Soothability Distress
Cry duration
Cry amount
Soothability
0.37
0.38
0.40
'All phi-coefficients are very significant at p<0.001.
0.25
0.34
0.31
Co-Morbidity of Crying Problems
prior to 5 months, then this different prediction is
also reported.
195
Table 3. The relationship of parent distress due to
crying and sleeping or flatulence at 5 months of age
Distress due to crying
RESULTS
Prevalence of Crying, Feeding and Sleeping
Problems
Different prevalences were found for the two
variables defining crying problems. More mothers
reported that crying occurred in above-average
amounts (17.1%) than for more than 2 hours per
day (4.8%). Difficult soothability was reported by
6.3% of mothers. More mothers were distressed by
their infant's crying (14.9%) than might have been
expected, given the rates of crying greater than 2
hours (4.8%) or difficulties with soothability (6.3%).
A further 17.2% of mothers had been distressed by
crying at some time since the birth of their infant,
but this distress had subsided by 5 months. Thus
about one in three mothers (32.1%) was distressed
by crying at some time during the first 5 months of
the infant's life.
Among other implications, these findings suggest that the different measures of crying and
distress caused by crying were tapping different
dimensions of early crying behaviour. To explore
this, the degree of convergence of cry measures is
examined by intercorrelations (phi-coefficients;
Table 2). Statistically very significant but only
moderately strong convergence between the different measures of crying and distress caused by
crying was found.
Night waking was reported for 21.5% of infants.
Nearly half of those with night waking problems
were awake for long periods at night (9.7% of all
infants). Distress concerning their infant's sleep
behaviour was reported by 13.8% of parents at 5
months.
Most mothers were bottle feeding at 5 months,
because either they had bottle fed since birth
(25.8%) or had changed from breast- to bottle
feeding sometime in the first 5 months (51.4%).
Only a few mothers were still fully (12.9%) or
partly (9.8%) breastfeeding at 5 months. Notably,
the most common feeding or gastrointestinal
problems reported were flatulence (9.3% at 5
months; 30.6% only prior to 5 months) and
vomiting (11.4% at 5 months; 5.1% only prior to 5
months), followed by problems with drinking
(2.6% at 5 months; 3.2% only prior to 5 months).
The average number of feeds/day was 4.6 + 0.9 and
the total time spent feeding was 56.8 ± 26.7
minutes/day at 5 months.
Night waking (%)*
Distress due to
sleeping (%)**
Flatulence (%)***
Previously
Still at 5 months
Still at 5
months
(N=64)
Only
previously
(N=74)
Never
(N=292)
32.8
28.6
25.7
10.8
18.2
11.4
12.5
35.0
29.5
13.6
11.6
12.4
***p<0.001; "p<0.01; .p<0.05.
The prevalence of night waking was 21.8% at 20
months and 13.3% at 56 months. Parents reported
that 12.1% of children had problems falling asleep,
27.1% co-slept with their children and 7.2% were
distressed about their child's sleep at 56 months
(see Wolke et al., 1994a).
Co-Morbidity of Crying with Sleeping and
Feeding at 5 Months
No significant co-morbidity of cry duration with
either sleeping or feeding problems was found. The
only significant association was that infants whose
crying was considered to be above average
amounts were more likely to have mothers who
were also distressed about infant sleep behaviour
(22.1% vs 12.0%, p<0.05). Soothability was not
related to any feeding variables, but it was related
to two of the three sleep measures. Infants that
were difficult to soothe more frequently had night
waking (44.4% vs 20.0%, p<0.01) and the parents
more often felt distressed by their infant's sleep
(37.0% vs 12.3%, p<0.01).
Crying impact measures were often related to
other behaviours. Mothers who were distressed by
crying at some time were also more likely to have
infants who woke regularly at night (29.0% vs
18.2%, p<0.05). Separate analyses showed that
night waking was most often found with infants
whose mothers were still distressed by crying at 5
months and least often for those never distressed
by crying (Table 3). Infants of mothers who had felt
distressed about crying only prior to 5 months had
night waking rates between these two extremes.
Mothers distressed by crying also felt more
distressed by their infant's sleep (19.0% vs 11.4,
p<0.05). Mothers who were still distressed by
crying at 5 months were also most frequently
D. Wolke, R. Meyer, B. Ohrt and K. Riegel
196
Table 4. Type of feeding and sleeping behaviour at 5 months
Feeding type
Changed to
Fully breastfed Partly breastfed bottle feeding
(N=215)
(N=54)
(N=41)
From birth
bottle fed
43.9
24.4
55.6
22.0
44.4
8.3
2.8
33.3
5.7
55.6
Night waking (%)**
Long arousals (total) (%)**
Of night wakers only (proneness; N=91)(%) 1
Distress due to sleeping (total)(%)*
Of night wakers only (proneness; N=91)(%) 2
46.3
16.7
36.0
26.4
56.0
18.1
9.3
51.3
14.0
69.2
(N=108)
*p<0.01; **p<0.001.
1Phi=0.17,NS.
2Phi=0.19,NS.
distressed by infant sleep (Table 3). In contrast,
mothers whose distress about crying had ceased by
5 months reported no more distress with their
infant's sleep than those who were never distressed
by crying (Table 3).
Distress about crying was also significantly
related to reports of infant flatulence (55.1% vs
32.9%, p <0.001). Separate analysis showed that
previous distress was related mostly to previous
occurrence of flatulence while continuous distress
was related to continuous flatulence problems
(Table 3).
Despite the large number of comparisons, significant associations tended to cluster at above
chance levels only around relationships between
crying and sleeping. Five of the 12 possible
associations among the four crying and three
sleeping variables were significant. In particular,
soothability and distress due to crying showed
significant associations with sleeping. By contrast,
only one of 28 comparisons among the four crying
and seven feeding variables was statistically
significant.
Co-Morbidity of Feeding with Sleeping at 5
Months
Mothers who were breastfeeding at 5 months were
more likely to have infants who were waking
regularly at night than those who were bottle
feeding (45.3% vs 14.9%, p<0.001). Night waking
was found to be similar for fully and partially
breastfed infants (Table 4). The lowest frequency of
night waking was found for infants bottle fed since
birth (Table 4). More breast- than bottle fed infants
woke for long periods at night (20.0% vs 7.1%,
p<0.001). Infants bottle fed from birth rarely woke
for long periods while one of four partially
breastfed infants did so (Table 4). To assess the
frequency of long night waking independent of the
base rate of night waking, the relative frequency of
long periods of waking among night wakers only
(i.e. proneness to long awakenings) as a function of
feeding type was computed. As shown in Table 4,
infants of mothers who had made clear decisions to
fully breast- or bottle feed were least prone to long
arousals once awoken, while partially breastfed
infants, and bottle feeders who had changed from
breastfeeding were prone to long arousals once
they had awoken. This difference was, however,
not significant due to the smaller sample of night
wakers only.
Breastfeeding mothers were also more often
distressed by their infant's sleeping than bottle
feeders (24.5% vs 11.3%, p<0.01). Separate analysis
(Table 4) showed that mothers who had bottle fed
from birth were the least distressed by sleep
behaviour while the mothers who were fully
breastfeeding were the most distressed by their
infant's sleep. Interestingly, fewer mothers were
distressed by their infant's sleep (13.8%) than there
were infants who were night wakers (21.5%), but
nearly all distressed mothers had infants who woke
regularly at night. However, one breast- and four
bottle feeding mothers reported distress due to
sleep even though their infants did not wake
regularly at night. Proneness to distress about
infant sleep was computed as the relative frequency of distress reports among night wakers as a
function of feeding type. As shown in Table 4,
those mothers who had changed from breast- to
bottle feeding were the most prone to report
distress about infant sleep, although this was not
statistically significant.
Flatulence was also related to mothers' reports of
night waking (27.9% vs 17.4%, p<0.05), long
Co-Morbidity of Crying Problems
Table 5.
197
Flatulence problems and sleeping behaviour at 5 months
Flatulence problems
Still at 5 months
(N=40)
Only previously
(N=132)
Never
(N=259)
35.0
22.5
64.3
25.0
71.4
25.8
11.4
44.1
18.3
64.7
17.4
6.9
40.0
9.8
48.9
Night waking (%)*
Long night time arousal (total)(%)*
Of night wakers only (proneness; N=93)(%) 1
Distress due to sleep (total)(%)**
Of night wakers only (proneness; N=93)(%)2
*p<0.05; **p<0.01.
'Phi=0.17,NS.
Thi=0.19,NS.
arousals at night (57.1% vs 38.0%, p<0.05) and
distress caused by sleep behaviour (19.9% vs 9.8%,
p<0.01). Infants who were reported to have
continuous problems with flatulence were most
frequently night wakers, woke for long periods
and were more likely to have distressed mothers
(Table 5). Previous problems with flatulence which
had since subsided were still related to more sleep
problems and increased proneness to distress due
to sleep at 5 months, although the latter was not
significant (Table 5).
The frequency of feeds and the total time spent
feeding were significantly related to night waking.
Infants who awoke regularly at 5 months averaged
one more feed/day than those who did not
(5.3+1.0 vs 4.4+0.7, p<0.001) and were fed longer
(62.1+27.6 vs 55.3 ± 26.3 min, p<0.05). Similarly,
infants who awoke for long periods at night were
10
o farLel/
0°
CC ‘
.,s.':'
,b
4'
• :
e,cl‘
Single Problem
,
61(
0-
,,c,•'4'
• cs0°
cc‘'
,,,,
A,co
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Regulatory Disordered
Figure 1. Pattern of co-morbidities of crying, feeding and sleeping problems at 5 months of age.
198
D. Wolke, R. Meyer, B. Ohrt and K. Riegel
Table 6. Distress due to crying as predictor of sleeping behaviour at 20 and 56 months of age
Distress due to crying (5 months)
Only previously
Still at 5 months
Never
(N=74)
(N=64)
(N=292)
Night waking at 20 months (%)**
Co-sleeping at 56 months (%)*
Distress due to sleeping at 56 months (°/0) •
32.8
35.9
10.9
29.2
35.1
12.9
17.3
23.3
5.0
**p<0.01; •p<0.05.
fed more often (5.1 + 0.8 vs 4.5 + 0.9, p<0.001) and
for longer (65.1 + 29.3 vs 55.9 + 26.3 min, p<0.05).
Finally, mothers who were distressed by their
infants' sleep fed their infants more frequently
than those not distressed (5.0 + 1.0 vs 4.5 + 0.9,
p<0.001), but there was no difference in total
duration of feeding. Gastrointestinal problems,
drinking problems and vomiting were not related
to sleep behaviour at 5 months.
Thus, feeding type, the number and duration of
feeds, and flatulence showed associations with
concurrent sleeping behaviour. Eleven of the 12
associations with the three sleeping variables were
significant. As the associations with sleeping were
similar for the above three variables, we investigated the convergence of feeding type with number
and duration of feeds. Breastfed infants were fed
more often than bottle feeders (5.3 +1.3 vs 4.4 +0.6,
p<0.001) and spent more time feeding
(68.9 +34.2 min vs 53.2 + 21.7, p<0.001). Fully
breastfed infants were fed most often (5.5 ± 1.5)
and for the longest durations (73.4 + 37.2 min).
Infants who had been switched to bottle feeding
or were bottle fed from birth were very similar, and
had the fewest meals (switch: 4.3 + 2.6; from birth:
4.4 + 0.7) and shortest feeds (switch: 52.7 + 21.9 min;
from birth: 54.2 + 21.4 min). Partially breastfed
infants were between fully breastfed and fully
bottle
fed
infants
(5.1 +1.0
feeds/day;
63.4 + 30.0 min/feed; p<0.001).
were reported in 14.6% of infants; a further 32.7%
had a single problem and 52.7% had no
problems. The relative frequencies of infants with
only one, two or all three problems are shown by
problem category in Figure 1. The frequency of
single sleep, feeding and crying problems as well
as combinations of these was similar. About 48%
of the crying, 52% of the feeding and 54% of the
sleep problems occurred without any comorbidity.
We determined whether mothers of 'regulatory
disordered' infants were more distressed by their
infants' crying or sleeping at 5 months than those
with just a single problem. More mothers were
distressed about crying if the infant was regulatory
disordered (47.6%) than if there was an isolated
problem of any type (16.3%) or no problems (4.9%,
p<0.001). Furthermore, an isolated cry problem was
less likely to be distressing (38.1%) than a cry
problem combined with a sleeping or feeding
problem (60.0%, p<0.001). Similarly, more mothers
were distressed about infant sleeping if the infant
was regulatory disordered (42.9%) than if there was
an isolated problem of any type (20.6%) or no
problems (1.3%, p<0.001). Little difference in the
reports of distress about sleeping was found,
however, if the infant had an isolated sleeping
problem (54.0%) or had a sleeping problem
combined with a crying or feeding problem
(62.8%).
Multiple Problems and Parental Distress
Later Sleep Problems: Single Predictors
Following DeGangi et al. (1991), infants were
defined as 'regulatory disordered' if they had at
least two of the following persistent problems at
5 months: a crying problem (cry duration > 2
hours/day, above average amount of crying, or
difficult to soothe: 20.1%), a feeding problem
(vomiting, problem with drinking, or flatulence:
21.6%) or a sleeping problem (night waking;
21.8%). Multiple problems (regulatory disorder)
Long crying duration and having felt distressed
about crying during the first 5 months were
significant predictors of night waking problems at
20 months. Infants with cry durations > 2 hours/
day at 5 months were more likely to wake regularly
at 20 months (42.1%) versus those with shorter
crying durations (21.0%, p<0.05). Similarly,
mothers who felt distressed by crying during the
first 5 months were more likely to have infants with
Co-Morbidity of Crying Problems
199
night waking problems at 20 months (30.9% vs
17.3%, p<0.01). Separate analyses showed that
those who continued to be distressed and those
who were only distressed by crying prior to 5
months had infants who woke more frequently
than those who never were distressed by crying
(Table 6).
None of the four cry measures were related to
night waking or problems falling asleep at 56
months, although there were some non-significant
tendencies in the expected directions. Co-sleeping,
however, was predicted by maternal distress about
crying in the first 5 months. Distressed mothers
were more likely to co-sleep with their infants at 56
months (35.5% vs 23.3%, p<0.05). Separate analyses
showed that co-sleeping was similar for mothers
still distressed at 5 months and for mothers who
had ceased to be distressed by crying by 5 months
(Table 6). Furthermore, mothers distressed by
crying in the first 5 months were more likely to
be distressed by their child's sleep at 56 months
(11.9% vs 5.0%, p<0.05). Again, there was no
difference whether the distress had continued until,
or only prior to, 5 months (Table 6).
There were a number of relationships between
feeding type or feeding problems and later sleep
behaviour. Infants who were breastfed at 5 months
more often had night waking problems at 20
months than bottle feeders (30.9% vs 18.8%,
p<0.05). Infants fully breastfed at 5 months were
most likely to wake at night at 20 months (35.8%),
followed by those partially breastfed (24.4%) and
those who had switched to bottle feeding (18.9%)
or were bottle fed from birth (18.7%, p<0.05). This
difference disappeared by 56 months. Night
wakers at 20 months were fed more frequently at
5 months (4.8 + 1.1 vs 4.5 + 0.8, p<0.05). This
tendency was still apparent at 56 months but not
statistically significant. Mothers who co-slept at 56
months fed more frequently at 5 months (4.8+1.1 vs
4.5 + 0.8, p<0.01). Total duration of feeds at 5
months was not related to later sleep behaviour.
Vomiting at or before 5 months was not related to
night waking at 20 months but was related at 56
months (21.1% vs 11.8%, p<0.05). In particular,
infants who had problems with vomiting at 5
months (26.5%) but not those with only previous
vomiting problems (9.1%) had night waking problerns (p<0.05). Mothers who had had an infant with
vomiting problems were also more likely to practise
co-sleeping at 56 months (37.1% vs 25.2%, p<0.05).
Again, those with vomiting problems at 5 months
were more frequently co-sleeping (41.7%) than those
with only previous problems (27.3%, p<0.06). A
significant association of gastrointestinal problems
at 5 months with problems in falling asleep at 56
months was found (29.2% vs 11.2%, p<0.05). This
was due to those infants who had had gastrointestinal problems before 5 months (42.9%) and not to
those whose problems were still present at 5 months
(10.0%, p<0.05).
In summary, crying amount, soothability, duration of meals, flatulence and drinking problems at 5
months were not predictive of later sleep behaviour. As shown only distress due to crying,
frequency of feeds and vomiting at 5 months
showed long-term associations with sleep in the
pre-school years.
Later Sleep Problems: Multiple-Problem Infants
Significant predictions as to night waking at 20
months and co-sleeping at 56 months were found for
both regulatory disordered and single-problem
infants (Table 7). There was a tendency for more
frequent night waking at 56 months in infants with a
single problem compared to infants with multiple or
no problems (p<0.07; Table 7). Furthermore, there
was a tendency for infants both with a single
Table 7. Later sleeping behaviour of infants with no, single or multiple problems (at 5 months of age)
Number of problems at 5 months
20 months
Night waking (%)***
56 months
Night waking (%)t
Co-sleeping (%)"
Distress (%)t
*"p<0.001; "p<0.01; tp<0.10.
No problem
(N=227)
Single problem
(N=141)
Multiple problems
(N=63)
13.8
31.7
27.4
10.2
20.9
4.5
18.6
34.5
10.4
12.9
33.3
9.7
200
problem and with multiple problems to have
mothers distressed about sleeping at 56 months
(p<0.09; Table 7). No associations of regulatory
disorder with problems falling asleep at 56 months
were detected. In general, the findings show that, for
predicting later sleep behaviour, it did not matter
whether the infant had only one or many problems at
5 months (Table 7).
To further investigate whether increased crying
per se, independent of sleep or feeding problems,
predicted later sleep behaviour, infants with only a
crying problem (without co-morbidity), infants
with a crying and other problems (crying and
feeding, or crying and sleeping, or crying, feeding
and sleeping problems) and infants without any
crying problem (i.e. no problems, single feeding or
sleeping problem, feeding and sleeping problems)
were compared. If increased crying is important for
prediction of later sleep behaviour, then only
infants with a crying or crying plus additional
problems should have later sleep problems more
frequently. No differences were found between
infants with no crying problem, only a crying
problem, or a crying plus other problems and sleep
behaviour at 20 and 56 months. The same type of
analyses were repeated for sleeping (no sleeping
problem, only a sleeping problem, sleeping plus
other problems) and feeding (no feeding problem,
only a feeding problem, feeding plus other problems). No differences among infants with no
feeding problems, only a feeding problem or a
feeding problem plus other problems were found
in relation to later sleep. By contrast, infants with
only sleep problems at 5 months (42.9%) or sleep
plus other problems (38.1%) more often had night
waking problems at 20 months compared to infants
without sleep problems (16.4%, p<0.001). Sleep
behaviour at 5 months tended to be related to night
waking at 56 months (sleep problem only: 24.0%;
sleep problem plus other problem: 9.5%; no
problem: 12.2%) but was not as statistically reliable
(p<0.06). Parents of infants who only had sleep
problems at 5 months (16.7%) were more distressed
by sleeping at 56 months than those who had sleep
plus other problems (7.1%) or no sleep problems
(5.8%, p<0.10) at 5 months. No significant relationships with co-sleeping and problems falling asleep
were found.
These analyses indicate that later sleep problems
are mainly related to the co-morbidity of either
crying or feeding problems with sleep problems at
5 months rather than to crying or feeding problems
per se. Stepwise logistic regressions were computed
to determine the independent contributions of
D. Wolke, R. Meyer, B. Ohrt and K. Riegel
crying, sleeping and feeding problems at 5 months
to 20 and 56 months' sleep behaviour. The criterion
for variables to enter the logistic function was set at
alpha <0.05. Night waking at 20 months was
predicted only by sleep problems at 5 months
(model chi-square: 22.4; df-1, p<0.001). Crying and
feeding problems made no additional contribution
to the prediction. The odds ratio of having night
waking problems at 20 months if sleep problems
were present versus not present at 5 months was
3.5. Maternal distress concerning sleep at 56
months was also predicted only by night waking
at 5 months (model chi-square: 3.9, df=1, p<0.05).
The odds ratio of distress at 56 months if sleep
problems were present at 5 months (versus not
present) was 2.3. Night waking, co-sleeping and
falling asleep at 56 months were not predicted by
sleeping, feeding or crying problems at 5 months.
Finally, logistic stepwise regressions were computed including measures of the impact of infant
problems (distress due to crying, distress due to
sleeping) and feeding behaviour (type, frequency
and duration of feeding) as predictor variables, in
addition to the three composite measures of crying,
sleeping and feeding problems at 5 months. Sleep
problems at 5 months remained the best predictor
of sleep problems at 20 months (p<0.001, odds ratio
3.3), with maternal distress about crying entering
the equation as an additional predictor (p<0.06;
odds ratio 1.8; model chi-square: 25.4 df=2,
p<0.001). Maternal distress about sleep at 56
months was best predicted by maternal distress
about crying at 5 months (p<0.05, odds ratio 2.4),
followed by sleep problems at 5 months (p<0.05,
odds ratio 2.3; model chi-square: 8.0, df=2, p<0.05).
Finally, co-sleeping practices at 56 months were
predicted by a higher number of feeds (p<0.01) and
presence of a feeding problem (p<0.05) at 5 months
(model chi-square: 12.0, df=2, p<0.01).
DISCUSSION
As part of a longitudinal community study on the
cognitive, motor and socioemotional development
of infants, the prevalence of crying, feeding and
sleeping problems, the co-morbidity of crying with
feeding and sleeping problems and the prediction
from crying and feeding behaviour in infancy to
later sleeping behaviour were analysed.
The prevalences of crying problems (20.1%) and
their impact (i.e. maternal distress about crying:
14.9%), sleeping problems (21.5%) and their impact
Co-Morbidity of Crying Problems
(13.8%) and feeding problems (21.6%) in this study
were generally comparable to those of previous
community studies of infants in western societies in
the first year of life using parent report measures
(see introduction). Nearly half of all infants (47.3%)
were reported to have a crying, sleeping or feeding
problem according to our definitions at 5 months.
The prevalences of sleep problems and sleeping
practices at 20 and 56 months of age were also
highly comparable to previous studies with preschool children (e.g. Jenkins et al., 1984; Klackenberg, 1968, 1971; Wolke et al., 1995a).
Co-Morbidity Patterns
The more 'objective' parent report measures of
duration and amounts of crying showed no or only
weak associations with sleep behaviour. In contrast, measures which assessed the impact of crying
on the mother (St James-Roberts, 1992, 1993), such
as distress due to crying, showed stronger associations, particularly with sleep behaviour. These
findings are in agreement with Weissbluth et al.
(1984a), who found associations between retrospective reports of colic and more frequent night
waking in infants at 4-8 months.
Aggregation of various crying and feeding
problem measures permitted comparisons of single
versus multiple problems of crying, feeding and
sleeping behaviours. Between 48 and 54% of the
crying, sleeping and feeding problems occurred
without any co-morbidity, while the remainder
showed overlap with problems in one or two other
areas of functioning (regulatory disordered infants,
Figure 1). The overall levels of co-morbidity of
crying problems with sleeping and feeding problems (50%) in this community sample are slightly
lower than those reported in two recent clinical
studies. In a sample of 3-4-month-old infant
referred for excessive crying, Wolke et al. (1994a)
reported that 70-80% of these infants had concurrent feeding problems and 50-80% had
concurrent sleep problems by maternal report.
Fifty to 80% of the mothers had previously seen
health professionals for these additional problems.
Papougek et al. (1994) reported moderate to high
levels of co-morbidity in their sample of infants
aged 1-24 months treated at their clinic for crying
babies. They reported that 53% had multiple
persistent problems in behavioural regulation,
while a further 26% had multiple problems
associated with psychological disturbances in the
parents at the time of referral. Not all parents of
excessively crying infants ask for help. Parental
201
impact of crying and help-seeking is dependent on
crying features and family factors such as the
number of older siblings (more siblings is associated
with lower impact), multiple births (higher impact),
social class (higher SES, higher impact), early
mother—infant relationship (early problems, higher
impact), caretaking support (lower support, higher
impact) and psychosocial problems (presence of
problems, higher impact) (Golding and Butler, 1986;
Hide and Guyer, 1982; St James-Roberts, 1992, 1993;
Wolke et al., 1994d). The higher rates of co-morbidity reported in clinical studies in comparison to
this and a British community study (Golding,
1986) are likely to be due to selective referral,
such that infants are referred when their parents
feel more distressed by infant crying and when
infants have multiple problems (Wolke et al.,
1994a; Papougek et al., 1994). However, having an
infant who wakes at night is enough to distress
parents independent of other behaviours (e.g.
crying or feeding) or daytime sleep behaviour.
Notable and somewhat surprising was the
relative lack of association between feeding type
and crying (Barr et al., 1989). Clinically, changes in
feeding have frequently been recommended for
crying problems (Woolridge and Fisher, 1988;
Breslow, 1957) and are adopted by parents with
and without paediatric advice (Barr et al., 1991;
Forsyth et al., 1985b). Changes from breast- to bottle
feeding are more often initiated by parents when
infants cry excessively (Golding and Butler, 1986;
Hide and Guyer, 1982; Loughlin et al., 1985). This
may change the pattern of crying by small amounts
in non-problem criers (Barr et al., 1989), but there is
no proof of its effectiveness in infants who cry
excessively (Forsyth et al., 1985a; Stahlberg and
Savilahti, 1986; Evans et al., 1981; Wolke and
Meyer, 1995). No differences in the prevalence of
colic in breast- versus bottle fed infants have been
found in previous community studies (Hide and
Guyer, 1982; Golding and Butler, 1986). Changing
feeding type may, however, affect parental perceptions and attributions: it may strengthen parents'
belief that their infants are vulnerable or have longterm health problems even when this is unfounded
(Forsyth and Canny, 1991; Warner and Hathaway,
1984; Wolke and Meyer, 1995). Furthermore, the
number or durations of feeds also did not differ
with duration or amount of crying, soothability or
distress caused by crying. Barr and Elias (1988) also
reported that shorter feeding intervals (and thus
more frequent feeding) had no influence on crying
at 4 months, although crying at 2 months was less
when feeding intervals were shorter.
202
Of the feeding problems, only the presence of
flatulence was related to distress caused by crying,
but it was not related to crying itself as reported by
the parents. Under- or overfeeding and gastrointestinal problems are the causes most commonly
implicated by pediatricians for excessive crying
(Keller et al., 1990; Woolridge and Fisher, 1988;
Breslow, 1957) despite a lack of empirical evidence
(Liebman, 1981; Miller and Barr, 1991d; St JamesRoberts, 1993; Danielsson and Hwang, 1985). The
most common interventions concentrate on feeding
changes or medication for flatulence (Keller et al.,
1990; Danielsson and Hwang, 1985). We did not
have information about frequency of consultations
or medications prescribed in this study, but
distressed parents may have adopted the explanation of flatulence often used by paediatricians to
explain crying in their infant.
Individual feeding problems such as vomiting,
drinking problems or gastrointestinal difficulties
were seldom related to sleep. In contrast, sleep
at 5 months showed strong associations with
feeding type and with feeding frequency and
duration. Breastfed infants awoke more frequently at night (e.g. Wright et al., 1983;
Eaton-Evans and Dugdale, 1988; Kleitman and
Engelmann, 1953; Wailoo et al., 1990) and were
also awake for longer at night. This is likely to
be due to breastfeeding the infant at night if
awoken (Van Tassel, 1985), which may account
in part for the shorter infant sleep durations
reported previously (e.g. Beal, 1969; Butte et al.,
1992; Elias et al., 1986; Keane et al., 1988). Thus
the relationship of frequency and duration of
feeds to night waking, night time arousal and
distress is mostly accounted for by feeding type.
These frequent and longer feeds may also
explain the greater distress reported by breastfeeding mothers who experience sleep
deprivation and poorer mood (Alder and Bancroft,
1988; Alder and Cox, 1983).
Consequences for Later Sleeping
Our findings clearly indicate that night waking
and parental distress about sleep at pre-school
age were not related to increased crying or
feeding problems per se (St James-Roberts and
Plewis, 1992), but rather that early night waking
persisted into the pre-school years (Wolke et al.,
1994b, 1995a; Jenkins et al., 1984; Zuckerman et
al., 1987). Distress about crying, breastfeeding and
number of feeds was predictive of later sleep, but
this is partly accounted for by their high
D. Wolke, R. Meyer, B. Ohrt and K. Riegel
association with sleeping difficulties at 5 months.
Learning to sleep through the night is highly
dependent on environmental cues and caretaking
practices (van Tassel, 1985), such as the choice to
breastfeed on demand.
In early infancy, frequent breastfeedings are
necessary to satisfy the physiological demands for
growth and brain development (Skuse et al.,
1994a,b,c.). In the second half of the first year,
breastfeeding at night is neither necessary nor
sufficient to maintain adequate growth (Habbick
and Gerrard, 1984; Skuse et al., 1994a; Wolke and
Skuse, 1992). Most infants will have been introduced to cereals and solid food (Heinig et al., 1993;
Wolke, 1994b) and growth hormones play an
increasing role in regulating growth (Karlberg et
al., 1987; Skuse et al., 1994a,b). Furthermore, by 6
months, neurophysiological sleep structure is comparable to that of adults (Coons and Guilleminault,
1982; Ferber, 1990; Wolke, 1994a,b), although
infants need more sleep and have several naps
during the day. Nervous system immaturity in
very pre-term infants is not related to impaired
development of day—night rhythms (Anders and
Keener, 1985; Shimada et al., 1993; McMillen et al.
1991) or later sleeping (Wolke et al., 1995a; Wolke,
1995). This is the best available evidence so far that
environmental cues rather than neurological
maturity are involved in the development of
circadian and ultradian rhythms and uninterrupted
night sleeping in infancy. Thus, there is no
apparent physiological reason to continue frequent
night time breast- or bottle feeding after 6 months.
Rather, as shown here and elsewhere, feeding
choice leads to different caretaking and interaction
patterns, especially at night (Butte et al., 1992; Elias
et al., 1986; Wright, 1993).
Co-sleeping and frequent breastfeeding is the
usual caretaking practice in most non-western
societies (Jackson, 1990; Barr, 1990b) including
highly industrialized countries such as Japan
(Caudill and Plath, 1966; Nugent et al., 1994)
and South Korea (Lee, 1992). However, night
waking, frequent night time feeds and co-sleeping
are often distressing to mothers in Germany
(Wolke et al., 1994b, 1995a) and other western
societies, where such practices are frequent but
not the norm (Johnson, 1991; Lozoff et al., 1984;
Barr, 1990b). Night waking of infants is often a
problem for the parents because it disturbs their
sleep, interferes with intimate partner relationships and affects daytime functioning (Minde et
al., 1993; Minden and Durand, 1993; Wolke,
1994b).
Co-Morbidity of Crying Problems
To conclude, our findings support Weissbluth et
al.'s (1984a; Weissbluth, 1986, 1987) assertions that
so-called 'post-colicky' sleep problems are likely to
be due to a failure of the parents to establish and
maintain regular sleep schedules. This is further
supported by the finding that treatments for colic
which do not alter caretaking such as medication
(Weissbluth et al., 1984b) or herbal teas (Weizman
et al., 1993) do not improve sleep behaviour. Only if
the older infant learns to self-control the process of
falling asleep (i.e. is not 'tricked' into sleeping by
feeding, filling up, long car rides or co-sleeping)
will s/he develop coping strategies to fall asleep
unassisted when waking at night (Ferber, 1987;
Mindell and Durand, 1993; Minde et al., 1993;
Pinilla and Burch, 1993; Schmitt, 1987; Wolke et al.,
1994b). Consequently, it is not because infants are
breastfed or co-sleep in infancy, but because
breastfeeding and co-sleeping are used as a way
of settling the infant to sleep that interrupted night
time sleep is maintained into the pre-school years
(Pinilla and Birch, 1993; Richman, 1981; Wolke,
1994a; Kataria et al., 1987). This conclusion does not
blame parents for sleep difficulties; rather, it
recognizes why many parents adopt strategies to
deal with night waking in the least conflictual
manner by night feeding or co-sleeping. This may
be especially true of parents who are dealing with a
temperamentally more difficult infant (Carey, 1989;
Weissbluth, 1986; Scher, 1992; Minde et al., 1993)
who is demanding in interactions during the day,
distresses the parents, affects their well-being
negatively and wakes them at night (Van den
Boom and Hoeksma, 1994; Miller et al., 1993;
Murray, 1994).
Study Limitations and Implications
We assessed prospectively the effects of crying or
feeding behaviour at 5 months on later sleep, but
did not assess the continuity of crying or feeding
behaviour. These data were not collected for
crying, and have not yet been entered for analysis
for feeding. Our data are based on parent reports in
interviews only. More detailed and reliable data
can be obtained by the use of diaries (e.g. Barr et al.,
1988; St James-Roberts et al., 1993; Wolke et al.,
1994e), but this was not possible in the current
study aimed at assessing a large range of family,
cognitive, neurological and somatic variables.
Nevertheless, parent perceptions of infant problem behaviour have ecological validity. They
determine whether parents seek help and make
use of health services (St James-Roberts, 1992).
203
It can be concluded that reports of increased
crying and distress caused by crying often do not
occur in isolation, but are accompanied by sleeping
or feeding problems as well. Whether these
infants are inherently physiologically regulatory
disordered (DeGangi et al., 1991; Lewis, 1992) or
caretaking practices mitigate against behavioural
organization of these infants cannot be concluded
with certainty. Studies of both behavioural phenotype and physiological organization are required.
Our findings, however, indicate that if conclusions
are to be drawn about the long-term effects of
increased or excessive crying (e.g. Forsyth and
Canny, 1991; St James-Roberts and Plewis, 1992),
these co-occurring problems need to be considered
for their contribution to that outcome. Further,
clinicians should be aware of co-morbidity when
treating colic if they aim to prevent long-term
problems such as sleep disturbances. Our understanding of underlying developmental mechanisms
will benefit from considering similarities and
differences in developmental changes of crying,
sleeping and feeding behaviours and in co-morbidity patterns in both normative and clinical samples
(Wolke, 1992, 1994a, 1995).
ACKNOWLEDGEMENTS
We would like to thank the numerous colleagues
who participated in the data collection and administration of the study. Special thanks are due to the
participating hospitals. The research has been
supported by grants PKE 24 (FKZ 0706 224) and
JUG 14 (FKZ 0706 564) of the Federal Government
of Germany, Ministry of Science and Technology
(BMFT).
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