Chronic fatigue syndrome (CFS) is a debilitating condition characterized by extreme fatigue that doesn't go away with rest. Other common symptoms of CFS include weakness, muscle pain, impaired memory, and sleep disorders.

While the cause of CFS is largely unknown, a number of factors are suspected to play a role. For instance, CFS is diagnosed two to four times as often in women than in men, for reasons unknown. CFS has also been associated—at one time or another—with low socioeconomic status, depression, psychological illness, stressful life events, high academic achievement, absence from school as a child, childhood behavior problems, obesity, history of infections such as mononucleosis and viral meningitis, high exercise levels, allergic tendencies, maternal over-protectiveness and/or depression, premature birth, birth weight, and birth order. None of these factors, however, come close to explaining why certain people develop CFS.

A large British cohort study that followed participants from birth until age 30 collected data on almost all of these potential risk factors. Their results, published in the October 5, 2004 issue of the British Medical Journal , failed to confirm any of them with few exceptions. Perhaps most significantly, their findings opposed previous research indicating that regular exercise increases the risk of CFS. Quite to the contrary, this study found that exercise during childhood was associated with a significantly reduced risk of developing CFS later in life.

About the Study

The 1970 British cohort study (BCS70) enrolled 16,567 babies born in England, Scotland, and Wales on April 5-10, 1970. The researchers collected data on the participants at birth, and ages 5, 10, 16, and 29-30. At age 30, the researchers used a self-report questionnaire to determine whether the participants had ever developed CFS.

Throughout the study, the researchers collected data from the participants and their parents, schoolteachers, and school doctors on the following factors potentially related to CFS:

Adulthood risk factors:

  • Socioeconomic status
  • Depression or psychiatric illness
  • Ethnicity

Childhood risk factors:

  • Socioeconomic status (age 10)
  • Gender, premature birth, birth weight, and birth order (at birth)
  • History of allergy (age 10)
  • Obesity (age 10)
  • Participation in sports (age 10)
  • Number of school days missed due to health or emotional problems (age 10)
  • “Presence of a longstanding condition in the child” and whether this condition “considerably limited the child’s daily life” (age 10)
  • Maternal or paternal severe or prolonged illness within past five years (age 10)
  • Maternal depression or psychiatric illness (ages 5, 10, and 16)
  • Behavior disorder (i.e., impulsivity/hyperactivity, attention deficit, and social development) (ages 5, 10, and 16)
  • Self-esteem (ages 10 and 16)
  • Psychological distress (age 16)
  • High intelligence (equivalent to IQ > 120 on cognitive tests; age 10)

The Findings

Out of the 11,261 participants who completed the study, 93, or 0.8%, reported ever having had CFS; and 48, or 0.4% reported currently having it – relatively low numbers.

A positive association was found between CFS by age 30 and the following risk factors: current depression (3 times as likely), female gender (twice as likely), having had a longstanding health condition as a child, and high , not low, socioeconomic status in childhood. Participants with CFS were three times as likely to be depressed, and twice as likely to be female, have had a childhood health condition, or a father in a professional or managerial occupation. No association was found between CFS and maternal depression, childhood depression or self-esteem, academic ability, parental illness, allergies, or birth order.

Only higher levels of spare time exercise in childhood were associated with a decreased risk of CHF in this study— by half. This is in contrast to a 1996 study concluding that patients with CFS were more than three times as likely to have exercised regularly prior to contracting their illness.

Somewhat mysteriously, while spare time exercise reduced the risk of CFS, more hours of sports played at school did not. Similarly, while having had a longstanding health condition during childhood that considerably affected home or school life was found to increase the risk of CFS, the number of days of school missed at age 10 (logically, as a result of such an illness) did not increase risk.

How Does This Affect You?

Though this study was large enough to detect a relatively rare condition, it suffered from some design limitations. For example, the presence of chronic fatigue syndrome was determined by self-report, not by a doctors’ diagnosis. And in the case of CFS, medical examination often determines an alternate explanation for a patient’s symptoms. For example, CFS can be confused with anemia, hypothyroidism, sleep apnea, hepatitis B and C, Cushing syndrome, dementia, and depression, among others. So some participants who reported they had CFS may have actually had a medical disorder resulting in their fatigue.

This study is helpful in excluding some previously suggested risk factors for CFS, such as having a depressed mother, and in identifying a potential risk modifier —exercise, but it does not help determine how or why CFS occurs. In fact, some of its findings are paradoxical and may even add to CFS’ enigmatic reputation.

What the study results do suggest, however, is that exercise during childhood may help protect against future CFS, so it adds to the already long list of reasons to encourage children to begin a life-long habit of regular, vigorous exercise.