Sleep problems linked to risk of fibromyalgia

Women with sleep problems have a higher risk of developing fibromyalgia than women who don’t have trouble sleeping, according to a large prospective Norwegian study.

The longitudinal study, published in Arthritis and Rheumatism (2012;64[1]:281-284), included 12,350 Norwegian women who didn’t have fibromyalgia, muscle pain, or physical impairment at baseline from 1984 through 1986. At follow-up from 1995 through 1997, 327 of the women reported fibromyalgia. Adjusted risk of fibromyalgia was 3.43 in women who said that they often or always had sleep problems compared with those who never experienced sleep issues. The association was somewhat, although not significantly, stronger in women aged 45 years or older. Those who reported having sleep problems often or always had an adjusted relative risk of 5.41 compared with a relative risk of 2.98 for women 20 to 44 years old.

“This study provides evidence of a strong dose-dependent association between frequency of sleep problems and risk of [fibromyalgia] in adult women,” the authors write. “Future studies should investigate whether early detection and treatment of sleep problems can reduce the risk of developing chronic widespread pain.”

How sleep problems lead to widespread musculoskeletal pain is uncertain, the authors note. Healthy people who experience sleep deprivation and interrupted slow-wave (stage 4) sleep have been found to develop mechanical hyperalgesia (symptoms similar to fibromyalgia) at many locations in the body. Sleep deprivation also can elevate plasma levels of markers of inflammation and decrease endogenous pain-inhibitory capacity. In fibromyalgia patients, sleep problems have predicted exacerbation of pain during 1-year follow-up. “It is therefore possible that long-lasting sleep problems render the individual more susceptible to development of chronic widespread pain, as well as exacerbation of such pain,” the authors theorize.

One limitation of the study is that it used a single question that didn’t allow for diagnosis of sleep disorders according to established standards, which could result in misclassification. However, the authors note that misclassification likely wouldn’t have differentiated between women who did and didn’t develop fibromyalgia. Another limitation was that the incidence of fibromyalgia was based on self-reports of physician-diagnosed disease, so some cases may not have fulfilled diagnostic criteria. The authors also note that they can’t rule out residual confounding of results by unknown and unmeasured factors (particularly anxiety) that affect sleep.

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