Departments of Psychiatry, University of Bristol, UK and University of Ioannina School of Medicine, Greece
Department of Psychiatry, University of Bristol, UK
Department of Psychiatry, University of Ioannina School of Medicine, Greece
Correspondence: Petros Skapinakis, Department of Psychiatry, University of Bristol, Cotham House, Cotham Hill, Bristol BS6 6JL, UK. E-mail: p.skapinakis{at}bristol.ac.uk
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ABSTRACT |
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Aims To present international data on the prevalence of unexplained fatigue and fatigue as a presenting complaint in primary care.
Method Secondary analysis of the World Health Organization study of psychological problems in general health care. A total of 5438 primary care attenders from 14 countries were assessed with the Composite International Diagnostic Interview.
Results The prevalence of unexplained fatigue of 1-month duration differed across centres, with a range between 2.26 (95% CI 1.17-4.33) and 15.05 (95% CI 10.85-20.49). Subjects from more-developed countries were more likely to report unexplained fatigue but less likely to present with fatigue to physicians compared with subjects from less developed countries.
Conclusions In less-developed countries fatigue might be an indicator of unmet psychiatric need, but in more-developed countries it is probably a symbol of psychosocial distress.
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INTRODUCTION |
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METHODS |
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In a previous paper we reported the overall prevalence of unexplained fatigue syndromes and their association with psychiatric disorders (Skapinakis et al, 2003), whereas in this paper we focus on the differences between centres.
Measures
The CIDI is a fully structured interview developed for use in
cross-cultural psychiatric epidemiology studies
(Wittchen et al,
1991). The modified version used in the present study includes
only the sections that assess mental symptoms common in primary care, notably
the sections on somatisation, anxiety, depression and hypochondriasis, as well
as a new section on neurasthenia. The primary care version rates both current
(1-month) and life-time symptomatology. Non-English-speaking participating
centres translated and back-translated the interview. Training and procedures
for assuring reliability are described elsewhere
(Von Korff & Üstün,
1995). The interviewerobserver reliability coefficient for
the primary care version of CIDI was found to be 0.92 overall, ranging between
0.81 and 1.00 for individual sections.
Measurement of fatigue: substantial unexplained fatigue
Fatigue was assessed using the neurasthenia section of the primary care
version of the CIDI. Three screening questions were put to all subjects: Q1
In the past month have you felt tired all the time?; Q2
Do you get easily tired while performing everyday tasks?; and Q3
Does even minimal physical effort cause exhaustion? Then the
interviewer asked a specific sequence of questions to determine the clinical
importance and possible cause of the symptom. Fatigue was considered
medically explained if a doctor had given the patient a definite
diagnosis or if there had been any abnormalities reported on examination or
further investigation. Subjects with medically unexplained fatigue were also
asked a fourth question that assessed the severity of fatigue: Q4 Is it
difficult to recover from these periods of fatigue or exhaustion when you
rest?
Subjects with medically unexplained fatigue (at least one positive answer to questions Q1-Q3) who answered positively to question Q4 were classified as cases of substantial unexplained fatigue. In comparison with the ICD10 definition of neurasthenia (World Health Organization, 1998), our definition of unexplained fatigue differs in that: it does not include the multiple somatic symptoms criterion (Criterion B in ICD10); it refers to 1-month duration instead of 3 (Criterion D in ICD10); and, it does not exclude other comorbid psychiatric disorders (Criterion E in ICD10). Therefore, it is a much broader definition compared with ICD10 neurasthenia.
Fatigue as the main reason for consultation
The above definition of fatigue is independent of whether the subjects
complained of fatigue to their primary care physician. For comparison, we also
report the prevalence of fatigue as a presenting complaint. Subjects were
asked to report the three main reasons for their consultation, choosing from a
list of symptoms. Those who reported weakness or lethargy (the only items in
the list related to fatigue) as one of their main reasons for consultation
were considered as having fatigue as a presenting complaint.
Measurement of morbidity
Psychiatric morbidity was assessed with the CIDI. Diagnostic algorithms
were developed to give diagnoses according to the ICD10 criteria. For
the purposes of the present study, subjects were classified as cases of
psychiatric morbidity if they had any of the following current ICD10
disorders: depressive disorders (including dysthymia); generalised anxiety
disorder; agoraphobia; panic disorder; somatisation disorder; and
hypochondriasis.
Chronic physical morbidity was assessed by asking patients whether they were suffering from a list of common chronic medical conditions. Patients were classified as cases of chronic physical morbidity if they were suffering from at least one chronic physical disorder.
Classification of primary care centres
Centres were entered into the analysis as dummy variables. However, for the
economic development hypothesis, centres were classified into three categories
according to the gross national income (GNI) per head in 2000 as follows:
high-income countries, with more than US$10 000 GNI per head (Athens, Berlin,
Groningen, Mainz, Manchester, Nagasaki, Paris, Seattle, Verona); middle-income
countries, with less than US$10 000 but more than US$1000 (Ankara, Rio de
Janeiro, Santiago); and low-income countries, with less than US$1000
(Bangalore, Ibadan, Shanghai). Data for the GNI per head were derived from the
World Bank databases available on the internet
(World Bank, 2000).
Analysis
All data analyses were conducted using Stata version 6.0
(Stata Corporation, 1999). The
weighted prevalence with 95% confidence intervals of fatigue syndromes was
estimated using the SVYPROP command. This command allows for sampling weights
and is suitable for the analysis of the two-phase design of the study
(Dunn et al, 1999). The association of GNI per head with fatigue was analysed by means of a series
of logistic regression models (separately for each fatigue syndrome) using the
SVYLOGIT command in Stata. We used fatigue case status (YesNo) as the
dependent variable, and the classification of centres according to GNI as the
independent variable, adjusting for socio-demographic variables, psychiatric
morbidity and physical morbidity. Odds ratios (with 95% CIs) of fatigue were
calculated for each category of the GNI variable. Psychiatric and physical
morbidity were entered into the models as binary variables. In all the
analyses we used sampling weights.
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RESULTS |
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Prevalence of fatigue syndromes
Table 1 shows the prevalence
of substantial unexplained fatigue and fatigue as a presenting complaint
across centres.
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Prevalence of substantial unexplained fatigue differed fifteen-fold across primary care centres (P<0.001). Centres with high prevalence of substantial unexplained fatigue (>10%) were Manchester, Santiago, Berlin, Groningen, Paris and Mainz, and centres with low prevalence (<4%) were Bangalore, Shanghai, Seattle, Verona and Ibadan.
Fatigue as a presenting complaint (either weakness or lethargy) was reported by 6.27% of the subjects (95% CI 5.47-7.18) with wide variation across centres. Centres with high prevalence of fatigue as a presenting complaint (>10%) were Bangalore, Ibadan, Nagasaki, Ankara and Paris, whereas centres with low prevalence (<2%) were Manchester, Seattle, Mainz and Verona.
In the whole data-set, very few subjects with substantial unexplained fatigue presented with fatigue (11%; 95% CI 8.21-14.57).
Association with level of economic development
In the logistic regression analysis, unexplained fatigue was associated
positively with GNI per head after adjustment for all other socio-demographic
variables, psychiatric morbidity and chronic physical morbidity. High-income
countries had an odds ratio of 2.62 (95% CI 1.67-4.11) compared with
low-income countries (Table
2).
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In contrast, fatigue as a presenting complaint was associated negatively with GNI per head, and subjects from higher-income countries had an odds ratio of 0.38 (95% CI 0.25-0.58) compared with subjects from lower income countries.
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DISCUSSION |
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Limitations and strengths
These results should be interpreted in the context of the following
limitations. First, this is a study carried out in primary care and therefore
the results cannot be generalised to the general population. Second, response
rates for the second phase baseline assessment were below 50% for five
centres. Therefore, a systematic bias in either direction cannot be ruled out,
even though participation was not related significantly to age, gender or
screening GHQ12 score. Third, although CIDI has been developed for use
in cross-cultural epidemiological research, this does not prove its cultural
validity. Fourth, medical causes of fatigue were excluded in a crude way by
asking patients if a doctor had given them a definite diagnosis for their
symptom or if there had been any abnormalities reported on examination or
further investigation.
Despite these limitations our study had the advantage of investigating fatigue in a large multicultural sample using the same methodology. We are not aware of any other studies that used such a culturally diverse sample. The present research was therefore able to study fatigue independently of the confounding effect of the sociocultural context.
Prevalence of fatigue syndromes across centres
The prevalence of substantial unexplained fatigue differed significantly
across centres, with an average prevalence of 7.99% (95% CI 7.13-8.85) in
primary care but with a range between 2.26 and 15.05 in different
countries.
The prevalence estimates reported from studies carried out in Western countries are generally consistent with the estimates provided here for similar countries. For example, Buchwald et al (1987) found a prevalence of unexplained chronic fatigue of 21% in an American primary care centre. In Australia, 24% of the primary care attenders reported substantial unexplained fatigue (Hickie et al, 1996), whereas in Canada 14% reported this (Cathebras et al, 1992). In UK primary care the prevalence of unexplained fatigue has been found to be approximately 10% (David et al, 1990; Wessely et al, 1997). By contrast, studies from the more-developed countries that used more culturally heterogeneous samples reported lower prevalence rates compared with the rates mentioned previously, for example 2% in a multiracial sample in San Francisco (Steele et al, 1998) and 6.4% in a study of ChineseAmericans in Los Angeles (Zheng et al, 1997). In the present study we also observed lower rates of fatigue in Asian countries.
Differences in the prevalence
In order to explain the reported differences in the prevalence of
unexplained fatigue we examined whether economic factors at the aggregate
level influence rates of fatigue. The classification of centres according to
the GNI per head for the country of location showed that subjects coming from
middle- or high-income countries were more likely to report substantial
unexplained fatigue compared with subjects from low-income countries.
Therefore, there is an indication that economic development might influence
the reporting of unexplained fatigue. It is worth noting that this pattern was
not found when similar analyses were carried out for other unexplained somatic
symptoms such as pain, headache, dizziness, excessive flatulence and
palpitations (data on file). These symptoms, unlike fatigue, tended to be less
prevalent in higher-income countries. Therefore, this finding cannot be
attributed to a general tendency for unexplained functional symptoms to be
reported more commonly in well-developed countries.
This is a difficult finding to interpret because economic development might be associated with many other (confounding) variables such as organisation of primary health care or local diagnostic preferences. To find out whether a similar pattern is observed for primary care patients, who presented to primary care physicians with complaints of weakness or lethargy (presenting fatigue), we carried out a similar analysis with the presenting complaint of fatigue as the dependent variable. This showed a very different picture; subjects from high- or middle-income countries were less likely to present with fatigue compared with those from low-income countries.
Past research in developed countries, in both the community and primary care, has shown that subjects with fatigue usually attribute their symptoms to psychosocial causes. For example, in a community study in the UK almost half of the subjects attributed fatigue to psychosocial causes such as work, family and lifestyle (Pawlikowska et al, 1994) and similar findings have been reported in primary care (David et al, 1990). If psychosocial explanations are prevalent then it seems reasonable that fatigue will not be a presenting complaint in primary care in developed countries. In that case, fatigue is more of a social metaphor rather than a legitimate or useful medical complaint (Lee & Wong, 1995). By contrast, in less-developed countries a somatic presentation might ensure an appropriate medical examination. This reminds us of the process of facultative somatisation described by Goldberg & Bridges (1988) where patients present with somatic symptoms as a ticket of admission to the primary care clinic. Simon et al (1999) have reported a similar finding in their study of the relation between somatic symptoms and depression. Analysing the same dataset used in the present study, they found that a somatic presentation of depression was more common at centres where patients lacked an ongoing relationship with a primary care physician. All the centres from low-income countries and most of the centres from middle-income countries were of this type.
Given the strong association of psychiatric disorders with fatigue (Skapinakis et al, 2000), we think that this finding might have important clinical implications. In less-developed countries, the complaint of fatigue might be an indicator of hidden psychiatric morbidity. By contrast, in more-developed countries, although syndromes of fatigue are common, they should not be always considered as evidence of unmet need as they might represent a common expression of psychosocial distress.
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Clinical Implications and Limitations |
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LIMITATIONS
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ACKNOWLEDGMENTS |
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Received for publication April 30, 2002. Revision received October 7, 2002. Accepted for publication October 21, 2002.