Latent Class Analysis of the Breadth, Severity and
Stability of Child Health Inequalities
Mensah FK, Nicholson JM, Headley L,
Carlin JB, Berthelsen D, Wake M
Acknowledgments
NHMRC Capacity Building Grant, MCRI, RCH and University of Melbourne
Professors Melissa Wake, John Carlin
Professor Jan Nicholson, Parenting Research Centre, Melbourne
Liz Headley, Victorian Public Health Training Scheme and Monash University
Professor Donna Berthelsen, Queensland University of Technology
Gender Equality Network, Economic and Social Research Council UK
Dr Wendy Sigle-Rushton, London School of Economics
Professors John Hobcraft and Kathleen Kiernan, Department of Social Policy
and Social Work and Institute of Effective Education, University of York
Multiple Outcomes of Health Inequality
Models have often focused on single outcomes
– fail to consider breadth of impact and address “multifinality”
Alternative strategies
– summary indices
– multiple outcome models
Example to follow: Impact of socioeconomic position on children’s
risks for multiple problems in physical, socio-emotional and
cognitive functioning
The Longitudinal Study of Australian
Children (LSAC)
Two national cohorts of ~5,000 children each
Infants (0-1 yrs) & Kindergarten children (4-5 yrs) in 2004
Followed up every two years
Conducted by Australian Govt. Department of Families, Housing, Community Services
and Indigenous Affairs (FaHCSIA), Australian Institute of Family Studies (AIFS),
and the Australian Bureau of Statistics (ABS) with advice from a national research
consortium
www.aifs.gov.au/growingup/
Physical, Psychosocial and Cognitive Difficulties at 4-5 (Birth cohort)
75
64.3
50
%
32.6
33.1
25
9.2
0
Most
advantaged
qu. 2
qu. 3
at least one problem in 2 or more domains
qu. 4
Least
advantaged
at least one problem in all 3 domains
Latent Class Analysis (LCA)
•
•
•
•
•
Groups children to reflect key differences
Accounts for inter-correlations between measures
Similar to cluster analysis, but is model based (probabilistic)
Gives model fit statistics to determine number of categories
Uses specialist software such as Mplus
E.g. Multiple problem behaviours in adolescence
Fergusson et al. 1994, Journal of Child Psychology & Psychiatry 35 (6) 1123-1140
Subtypes and severity of peer victimisation
Nylund et al. 2007, Child Development 78 (6) 1706-1722
Study design
Age 4-5
Age 6-7
Age 8-9
K cohort (wave 1) (N=3,711)
K cohort (wave 2) (N=2,563)
K cohort (wave 3) (N=3,080)
B cohort (wave 3) (N=3,608)
(replication sample)
Indicators and Measures
Global health measure
Excellent / Very good / Good / Fair or Poor
Special health care needs
No / Yes (condition lasting for at least 12 months requiring
medicines, medical care, health or educational services )
Asthma diagnosis
No / Yes
Sleep difficulties
0,1,2+ (getting to sleep, sleeping alone, waking during the night)
Injuries
0,1,2+ in the last year
Body mass index
Underweight / Normal / Overweight / Obese
Peds Quality of Life
Physical, Social, Emotional and School Scores
Strengths and Difficulties
Pro-social, Conduct, Emotional, Hyperactivity and Peers Scores
Peabody Picture vocabulary test
Direct Assessment of Language Development
Who am I? (Age 4-5)
Direct Assessment of School Readiness
Teacher rating scales (Age 6-7, 8-9)
Language and Literacy, Mathematical Thinking
Model fit parameters (K cohort age 4-5)
278,000
Akaike information criteria (AIC)
Bayesian information criteria (BIC)
Adjusted BIC
276,000
274,000
272,000
270,000
268,000
266,000
1
2
3
4
Number of classes
5
6
P value
0.000
0.014
0.048
0.188
0.327
Classes
0.75
0.25
0.59
0.33
0.07
0.55
0.20
0.19
0.07
0.45
0.22
0.20
0.09
0.05
0.38
0.22
0.15
0.12
0.09
0.04
Profiles from 3 class model (K cohort age 4-5)
Mean score for
Peds Quality of Life:
Healthiest
(59.5%)
Moderate
(33.4%)
Severe
(7.2%)
Physical
87.1
79.8
63.0
Social
90.3
77.4
52.1
Emotional
78.5
64.4
56.8
School
93.3
83.8
58.2
Pro-social
8.3
7.0
6.8
Conduct difficulties
1.7
3.7
3.6
Emotional difficulties
1.1
2.3
3.7
Hyperactivity
2.7
4.6
5.0
Difficulties With Peers
1.1
2.2
3.2
Language
PPVT
65.0
63.6
59.7
School readiness
Who am I
65.2
63.4
61.1
Strengths and difficulties
Profiles from 3 class model (K cohort age 4-5)
Percent of children with
Healthiest
(59.5%)
Moderate
(33.4%)
Severe
(7.2%)
Fair or poor health
1.0
3.1
9.3
Special health care need
7.2
17.2
38.6
Asthma diagnosis
16.9
26.5
34.0
2 or more sleep problems
7.1
21.3
23.3
2 or more injuries
2.8
6.3
6.9
Underweight
4.9
5.0
7.0
Overweight/obese
19.3
20.4
21.1
Replication and consistency of 3 class structure
B cohort
K cohort
Age 4-5 (%)
Age 4-5 (%)
Age 6-7 (%)
Age 8-9 (%)
(N=3,608)
(N=3,711)
(N=2,563)
(N=3,080)
Healthiest
54.7
59.2
60.3
54.9
Moderate
38.4
33.4
30.5
36.5
Severe
6.9
7.4
9.2
8.6
Common sample across 3 waves of the K cohort N=1,685
Age 4-5 (%)
Age 6-7 (%)
Age 8-9 (%)
Healthiest
64.7
64.2
60.0
Moderate
30.1
29.0
33.5
Severe
5.2
6.7
6.6
Classification (K cohort age 4-5)
ESTIMATED CLASS PROPORTIONS AND COUNTS
1
(Healthiest)
0.592
2196
2
(Moderate)
0.334
1241
3
(Severe)
0.074
274
CLASSIFICATION QUALITY (Entropy) 0.809
CLASSIFICATION OF INDIVIDUALS BASED ON THEIR MOST LIKELY LATENT
CLASS MEMBERSHIP
1
(Healthiest)
0.595
2208
2
(Moderate)
0.334
1238
3
(Severe)
0.072
265
A further technique for classification after LCA
Technique of random draws on the basis of probabilities
http://www.statmodel.com/download/meantest2.pdf
Takes into account both bias and uncertainty
Similar principles to multiple imputation
Implemented in Mplus as a default
Can also be implemented in Stata
Feeds into descriptive analysis and regression models
Health Inequalities - K cohort age 4-5
Most
healthy
(%)
Moderate
(%)
Severe
(%)
Moderate
69.5
27.7
2.8
Severe
69.2
27.7
3.1
3rd Quintile
69.3
24.4
6.3
4th Quintile
56.6
36.2
7.2
Least advantaged
47.5
37.9
14.6
Most advantaged
61.2
33.0
5.9
2nd Quintile
63.0
31.3
5.6
3rd Quintile
56.7
36.6
6.7
4th Quintile
54.0
39.2
6.9
Least advantaged
39.4
43.4
17.2
Girls
Most advantaged
2nd Quintile
Boys
0
0.2
0.4
0.6
Proportion of children
0.8
Stability through childhood (K cohort)
Age 4-5
Age 6-7
Age 6-7
Healthiest
(%)
Severe
(%)
Age 8-9
Healthiest
(%)
Moderate
(%)
Moderate
(%)
Severe
(%)
Healthiest
78.8
18.5
2.8
73.0
25.5
1.5
Moderate
41.2
50.1
8.7
39.6
48.6
11.8
Severe
16.5
38.9
44.6
15.7
45.3
39.0
Healthiest
77.7
22.0
0.3
Moderate
31.1
55.7
13.3
Severe
15.5
47.3
37.2
Conclusions, continuation and discussion
Clear and reproducible groups reflecting degree of difficulties
Powerful social grading
Strong continuity from early to mid-childhood
Potential to examine predictors, prognosis and associated costs
For discussion:
Criteria for evaluating validity
Utility of this type of indicator beyond academic research