5.7
Chronic Fatigue
5.7.1
Fatigue at follow up
In the follow up study questionnaire, participants were asked whether they had experienced
extreme tiredness or fatigue following normal activities in the previous 12 months and
whether they had experienced prolonged fatigue (extreme tiredness or fatigue of at least one
month’s duration) in the previous 12 months and chronic fatigue (extreme tiredness or
fatigue of at least six month’s duration) in the previous 12 months. These questions
comprised a subset of a larger structured questionnaire administered by the assessing
doctor in the baseline study medical assessment. The Chalder Fatigue Scale (CFQ)47 was
used as an additional measure of fatigue, but in the follow up study only.
Extreme tiredness or fatigue, prolonged fatigue and chronic fatigue at
follow up
Figure 1 and Table 1 show the prevalence of participants who reported fatigue related
outcomes in the past 12 months at follow up. Gulf War veterans reported all of the fatigue
outcomes in the past 12 months statistically significantly more commonly than did the
comparison group, with the risk in Gulf War veterans estimated to be between 37% and 41%
higher than that in the comparison group (Table 1).
Figure 1 Percentage of participants who reported extreme tiredness or fatigue, prolonged
fatigue (at least 1 month duration) or chronic fatigue (at least 6 months duration) in the past 12
months
Australian Gulf War Veterans’ Follow Up Health Study: Technical Report 2015
Page 111
Table 1 Prevalence and Risk Ratios for fatigue, prolonged fatigue and chronic fatigue at follow
up
Gulf War veterans
N=697
Comparison group
N=659
n (%)
n (%)
RR
Adj RR (95% CI)
Extreme tiredness/fatigue in
past 12 months
Prolonged fatigue (≥ 1 month)
228 (32.8)
150 (22.9)
1.43
1.38 (1.15-1.65)
117 (16.9)
74 (11.3)
1.49
1.37 (1.04-1.80)
Chronic fatigue (≥ 6 months)
86 (12.4)
53 (8.1)
1.53
1.41 (1.02-1.96)
Fatigue outcome in the past
12 months
Fatigue severity assessed using the Chalder Fatigue Scale at follow up
Table 2 shows that the median total CFQ scores, and the median Physical- and Mentalfatigue component scores, each indicative of severity, were very similar between the two
study groups. However, a greater proportion of Gulf War veterans (33%) than comparison
group participants (26%) were defined as CFQ cases. This difference between groups was
significant with the risk of CFQ caseness estimated to be 23% higher in Gulf War veterans
than in the comparison group.
Table 2 Chalder Fatigue Scale (CFQ) fatigue scores and caseness by study group
Chalder Fatigue Scale
measure
Gulf War veterans
N= 697
Comparison group
N= 659
Median (IQR)
Median (IQR)
Adj Median diff (95% CI)
12 (11-16)
11 (11-15)
0.5 (0.01–0.99)
Physical fatigue score
7 (7-11)
7 (7-9)
0 (-0.31, 0.31)
Mental fatigue score
4 (4-6)
4 (4-5)
0 (-0.07, 0.07)
n (%)
n (%)
Adj RR (95% CI)
232 (33.3)
170 (25.8)
1.23 (1.04–1.45)
Total fatigue score
CFQ fatigue caseness
5.7.2
Association between Gulf War deployment characteristics
and chronic fatigue in veterans at follow up
The associations between Gulf War deployment characteristics and chronic fatigue at follow
up in male Gulf War veterans are shown in Table 3. In general, the risk of chronic fatigue
was highest in Army Gulf War veterans relative to the Navy and Air Force, and amongst
those veterans who served under non-supervisory ranks relative to higher ranks, however
these differences did not achieve statistical significance. Age at the time of the Gulf War
deployment was also not associated with chronic fatigue at follow up.
Australian Gulf War Veterans’ Follow Up Health Study: Technical Report 2015
Page 112
Table 3 Association between Gulf War-deployment characteristics and chronic fatigue at
follow up in male Gulf War veterans
Gulf War exposure
Gulf War veterans with chronic fatigue
Age at deployment
N
n (%)
RR
Adj RR (95% CI)
< 20
62
9 (14.5)
1.00
1.00
20-24
170
25 (14.7)
1.01
1.18 (0.57-2.42)
25-34
364
41 (11.3)
0.78
1.11 (0.48-2.55)
>=35
100
11 (11.0)
0.76
1.07 (0.40-2.90)
Navy
599
76 (12.7)
1.00
1.00
Army
45
7 (15.6)
1.22
1.35 (0.63-2.86)
Air Force
52
3 (5.8)
0.45
0.50 (0.16-1.54)
Officer
148
16 (10.8)
1.00
1.00
Other rank-supervisory
354
39 (11.0)
1.02
0.99 (0.56-1.74)
Other rank - non supervisory
193
31 (16.1)
1.49
1.43 (0.70-2.91)
Service branch
Rank category
5.7.3
Change in prevalence, also persistence, remittance and
incidence of chronic fatigue since baseline
In male participants who completed questions relating to fatigue outcomes at baseline and
follow up (697 Gulf War veterans and 659 comparison group) Table 4 shows that the
prevalence of prolonged fatigue and chronic fatigue more than doubled from baseline to
follow up, and these increases were statistically significant.
Additional analysis showed that there was no difference between the two groups with
respect to change over time for prolonged fatigue (RR=0.88; 95% CI 0.55-1.39) or chronic
fatigue (RR=0.76; 95% CI 0.43 – 1.35).
Table 4 Prevalence of prolonged fatigue and chronic fatigue at baseline and follow up
Gulf War veterans (N=697)
Comparison Group (N=659)
Baseline
prevalence
n (%)*
Follow up
prevalence
n (%)
RR (95% CI)
Baseline
prevalence
n (%)*
Follow up
prevalence
n (%)
RR (95% CI)
Prolonged
fatigue
50 (7.3)
117 (16.9)
2.32 (1.77–3.05)
26 (4.3)
74 (11.3)
2.66 (1.82–3.88)
Chronic fatigue
41 (6.0)
86 (12.4)
2.08 (1.52–2.85)
18 (3.0)
53 (8.1)
2.72 (1.68–4.39)
* Includes only those participants who were assessed for fatigue at follow up
Table 5 shows the proportion of Gulf War veteran and comparison group participants with
chronic fatigue present or absent at baseline and at follow up. Incident cases are shown in
the first row of data in Table 5 as absent at baseline and present at follow up. Of the 643
Australian Gulf War Veterans’ Follow Up Health Study: Technical Report 2015
Page 113
Gulf War veterans and 582 comparison group participants who had not reported chronic
fatigue at baseline, 10.4% and 7.4%, respectively, were incident cases who met criteria for
chronic fatigue at follow up. This difference between groups in incidence risk was not
statistically significant.
Persistent cases are shown in the second row of data in Table 5 as present at baseline and
present at follow up, whilst remitted cases are present at baseline and absent at follow up.
Of the 41 Gulf War veterans and 18 comparison group members who had reported chronic
fatigue at baseline, 18 (43.9%) Gulf War veterans and 7 (38.9%) comparison group
participants were persistent cases who also reported chronic fatigue at follow up, whereas
56.1% and 61.1% remitted. The differences in persistence and remittance, between the Gulf
War veterans and the comparison group, were not statistically significant.
Table 5 Persistent, remitted and incident cases of chronic fatigue among participants at
baseline and follow up
Chronic fatigue
Gulf War veterans (N=682)
Comparison group (N=597)
Follow up
Baseline
Follow up
n (%)
n (%)
absent
present
Absent (n = 643)
576 (89.6)
67 (10.4)*
Present (n = 41)
(56.1)††
(43.9)†
23
18
Baseline
n (%)
n (%)
absent
present
Absent (n = 582)
539 (92.6)
43 (7.4)*
Present (n = 18)
(61.1)††
7 (38.9)†
11
Between groups
RR
Adj RR
95% CI
Incidence
1.41
1.36
0.94 – 1.97
Remittance
0.92
1.08
0.71 – 1.65
Persistence
1.13
0.87
0.46 – 1.66
* Incident cases
† Persistent cases
†† Remitted cases
5.7.4
Key findings
All fatigue related outcomes in the past 12 months; extreme tiredness or fatigue, prolonged
fatigue of at least one month duration, and chronic fatigue of at least six months duration;
were increased in Gulf War veterans at follow up relative to the comparison group, based on
the same definitions that were used at baseline. Furthermore, fatigue caseness was also
increased as defined by the Chalder Fatigue Scale although fatigue severity was similar
between the study groups.
The prevalence of prolonged fatigue and chronic fatigue more than doubled in both groups
at follow up compared with baseline. Amongst Gulf War veterans there was a greater
Australian Gulf War Veterans’ Follow Up Health Study: Technical Report 2015
Page 114
incidence of new chronic fatigue cases since baseline than in the comparison group,
however this difference was not statistically significant, while remittance and persistence
were similar in the two groups. There was no clear association between chronic fatigue at
follow up and Gulf War-related service branch, rank or age category.
Australian Gulf War Veterans’ Follow Up Health Study: Technical Report 2015
Page 115