People with fibromyalgia and chronic fatigue syndrome may do best with individually tailored plans for physical activity — and ideal sleep hours — a study suggests, after finding that patients who exercised, or slept, either very little or a lot reported greater symptom severity than those who were moderate in their behavior.

The study, “Physical Activity and Sleep in Chronic Fatigue Syndrome and Fibromyalgia Syndrome: Associations with Symptom Severity in the General Population Cohort LifeLines,” was published in the journal Pain Research and Management.

Chronic fatigue syndrome (CFS) and fibromyalgia (FM) are disabling health conditions collectively known as functional somatic syndromes. The two often overlap, with substantial numbers of CFS patients meeting the criteria for fibromyalgia (disabling and unexplained fatigue and musculoskeletal pain, respectively) and vice versa, the study noted.

Both diseases are also thought to have varied causes that include biological, psychological, and social factors.

“Recent research suggests that both avoidance of activity and overactivity are associated with an increase in symptom severity, including pain and fatigue. This indicates that, in patients with CFS and FMS [fibromyalgia syndrome], both high and low levels of physical activity may result in higher symptom severity, comparable to what is observed in the general population,” the researchers wrote.

But the role of physical activity and sleep in the development and progression of CFS and FM is not well understood, and studies into activity and sleep levels of both groups of patients — and their impact on disease symptoms — are lacking.

Researchers in the Netherlands examined whether chronic fatigue and fibromyalgia patients — compared by disease group and against a control group of people without either disease — have different levels of physical activity and sleep duration, and how that affects their symptoms.

They hypothesized that either too much or too little physical activity and sleep are related to symptom severity, and used the LifeLines cohort study — a general population study — to enroll participants and access their data. The study covered 91,453 people, of which 943 had chronic fatigue, 2,714 had fibromyalgia, and 87,532 had neither disease and served as a control group.

Using questionnaires, researchers assessed physical activity, sleep duration, and symptom severity in the patients. They analyzed the data after adjusting for age, sex, body mass index, smoking, and educational level.

Activities rated included “commuting activities (walking or bicycling to/from work or school), leisure-time activities (walking, bicycling, gardening, and odd jobs), sports activities, household activities, and activities at work and school,” the study said. Each were further evaluated as to intensity (slow to fast workout), duration and frequency (number of times each week).

Symptom severity was measured using a 12-item questionnaire that looked at the intensity of various symptoms (from fatigue to muscle pain, numbness and tingling, nausea, etc.)

Results showed that both groups of patients had significantly lower physical activity scores compared to controls, but no significant differences were seen in activity levels between these two sets of patients.

People with chronic fatigue, not surprisingly, slept longest on a regular basis (average of 466 minutes) compared to fibromyalgia patients (450 minutes on average) and controls (446 minutes).

Both relatively low and high physical activity scores — and relatively short and long sleep times — were associated with higher symptom severity by all three groups of participants, people with fibromyalgia, chronic fatigue and neither disease. But those who serves as controls and had “a higher physical total activity score or longer sleep duration reported a slightly lower symptom severity,” the researchers said.

“This study indicates that patients with CFS or FMS sleep longer and are less physically active than controls on average,” the study concluded. “Both low and high levels of physical activity and short and long sleep duration are associated with higher symptom severity, suggesting the importance of patient-tailored treatment.”