Being overweight or obese is a strong and independent risk factor for the future development of fibromyalgia in women, particularly for those who are inactive, a Norwegian study found.
Studies have shown lower levels of physical fitness among patients with fibromyalgia compared with healthy controls.
In addition, high body mass index — which may reflect poor physical fitness — has been linked with a lower pain threshold among patients with fibromyalgia.
Because it has not been determined whether poor physical fitness contributes to the development of fibromyalgia or is a consequence of the disease, Mork and colleagues conducted a longitudinal study that included 15,990 women ages 20 years and older who were healthy at baseline.
The analysis also found a non-significant tendency toward a dose-response effect for physical activity, with women who reported exercising at least four times per week having a 29% lower risk of fibromyalgia compared with those who were inactive.
Women who exercised for two hours or more per week had a lower relative risk.
The risk was more than twofold higher for obese or overweight women who exercised less than one hour per week.
Although the precise mechanisms by which obesity contributes to widespread pain in fibromyalgia are unknown, some etiologic factors seem to be shared by the two conditions.
For example, elevated levels of proinflammatory cytokines have been found in obese subjects and in patients with fibromyalgia, but further studies are needed to clarify the relationship.
Dysregulation of the hypothalamic-pituitary-adrenal function also has been identified both in the obese and in patients with fibromyalgia.
“An autonomic dysfunction may therefore contribute to enhanced pain and other symptoms associated with [fibromyalgia] (e.g., disturbed sleep,
fatigue) by alterations of the physiologic responses required for adequate stress management and pain inhibition.”
In addition, the well recognized temporary pain relief that follows aerobic exercise, probably through the body’s natural pain relief system, may contribute protective effects against chronic pain.
Limitations of the study include the possibility that inactive women might have been less likely to participate in the survey, so the estimated relative risks may have been underestimated.
“Community-based measures aimed at reducing the incidence of [fibromyalgia] should emphasize the importance of regular physical exercise and maintenance of normal body weight,” they concluded.
Primary source: Arthritis Care & Research Source reference: Mork P, et al “Association between physical exercise, body mass index, and risk of fibromyalgia: longitudinal data from the Norwegian Nord-Trøndelag Health Study” Arthritis Care Res 2010; 62: 611-17.