Epidemiology of chronic fatigue syndrome and self reported myalgic encephalomyelitis in 5-15 year olds: cross sectional study

Chronic fatigue syndrome is characterised by severe physical and mental fatigue associated with disability, which by definition markedly affects people's lives. At one end of the spectrum, newspaper headlines imply that chronic fatigue syndrome or myalgic encephalomyelitis in children is of epidemic proportions, whereas at the other end the existence of the disorder is refuted. Attempts have been made to assess the size of the problem in the community, general practice, schools, and secondary care.^w1-w5 Methodological problems, however, such as selection biases and poor response rates make it difficult to draw conclusions from these studies. We are unaware of any population studies in the United Kingdom that examine the prevalence of and factors associated with chronic fatigue syndrome in children. We determined the prevalence of chronic fatigue, chronic fatigue syndrome, and reported myalgic encephalomyelitis in 5-15 year olds and examined demographic and psychiatric associations.

Methods and results

This study was part of a larger study, carried out in 1999 by the social survey division of the Office for National Statistics to find out the prevalence of mental disorders in children aged 5-15. A total of 14 250 families were contacted, 931 (6.5%) opted out, and 790 (5.5%) of addresses were ineligible. Families living in private households in England, Scotland, and Wales were sampled.¹

Altogether 10 438 of 12 529 mothers were asked whether the index child had myalgic encephalomyelitis or chronic fatigue syndrome and completed the 12 item general health questionnaire.² The sample for the interview study consisted of 4240 11-15 year old children identified from this sample, and they were asked whether they had been feeling more tired and worn out than usual. If they answered affirmatively the interviewer asked supplementary questions relating to duration, effect of fatigue on different aspects of their life, and number and severity of symptoms. We used the development and wellbeing assessment to assess psychiatric disorder.³

Table 1.

Relation between dependent variables and self reported chronic fatigue, criteria from the US Centers for Disease Control and Prevention (CDC) for chronic fatigue syndrome, and parental report of myalgic encephalomyelitis or chronic fatigue syndrome (multivariate analysis). Values are odds ratios (95% confidence intervals) unless otherwise indicated

	Self reported	CDC criteria	Parental report*
No (%) of respondents	24/4240	8/4240	4/10 438
Prevalence (95% CI)	0.57 (0.34 to 0.80)	0.19 (0.06 to 0.32)	0.038 (0.00 to 0.076)
Age†	1.5 (1.1 to 2.1)	1.9 (1.0 to 3.7)	1.2 (0.9 to 1.8)
	P<0.01	P=0.03	P=0.2
Female sex	1.4 (0.6 to 3.3)	0.8 (0.2 to 3.4)	0.9 (0.1 to 7.1)
	P=0.4	P=0.8	P=0.9
Mother's score on general health questionnaire†	1.0 (0.9 to 1.2)	1.2 (0.9 to 1.4)	1.3 (1.0 to 1.6)
	P=0.6	P=0.1	P=0.03
Any anxiety disorder	3.7 (1.2 to 12.0)	8.8 (1.8 to 43.5)	4.6 (0.4 to 48.3)
	P=0.03	P=0.008	P=0.2
Any depressive disorder	2.8 (0.6 to 12.2)	1.2 (0.1 to 12.3)	0.0 (0.0 to 2.86×10−33)
	P=0.1	P=0.9	P=0.8

^*Includes one child aged 6.

^†For continuous variables, odds ratios represent a one point shift on the scale.

Chronic fatigue was defined as severe fatigue of at least six months' duration, for which rest did not help and which led to functional impairment of the child. Chronic fatigue syndrome was defined according to the criteria of the US Centers for Disease Control and Prevention (CDC).⁴

We used logistic regression to examine associations in terms of odds ratios between independent and dependent variables. We conducted interviews with 10 438 of 12 529 eligible children. Failed interviews were due to either non-contact (n = 317) or refusal (n = 1774). The table shows risk factors for each of the three main outcomes. The risk factors for chronic fatigue and CDC criteria for chronic fatigue syndrome were older age and anxiety disorders. Parental report of myalgic encephalomyelitis or chronic fatigue syndrome was associated with maternal distress on the general health questionnaire. Female sex was not a risk factor for any outcomes.

Comment

Symptomatic fatigue in children is common, but chronic fatigue and chronic fatigue syndrome are relatively rare. The rates of the syndrome that we report are lower than those found in equivalent surveys in adults. Cases where children are labelled as having myalgic encephalomyelitis or chronic fatigue syndrome are even less common. Given the small numbers, the results obtained in the subsequent analysis cannot be precise. We found no concordance between parental labelling that a child had myalgic encephalomyelitis and operationally defined chronic fatigue syndrome. We found a strong association between psychiatric disorder and these outcomes, which is a consistent finding among adults with chronic fatigue syndrome. Maternal psychological distress was associated with parental report of myalgic encephalomyelitis or chronic fatigue syndrome, but given the cross sectional nature of the data it is impossible to determine the direction of causality.