Women experiencing insomnia are twice as likely to develop fibromyalgia as women without sleeping problems, a study suggests. Exercise may lessen such risk, researchers report.

The study, “The joint effect of insomnia symptoms and lifestyle factors on risk of self-reported fibromyalgia in women: longitudinal data from the HUNT Study,” was published in BMJ Open.

Fibromyalgia is a chronic condition characterized by widespread pain, fatigue, and disturbed sleep. Difficulties with sleep onset, maintenance, and persistent non-restorative sleep are particularly distressing to fibromyalgia patients.

“Almost all women with fibromyalgia report some sleep problems,” the researchers said.

Although the association between chronic widespread pain and insomnia is bidirectional, evidence suggests that sleep impairment may have a stronger impact on chronic pain than vice versa.

“Epidemiological studies indicate insomnia symptoms increase the risk of fibromyalgia and widespread pain among an otherwise healthy population,” the team stated.

However, it is not clear whether the number of insomnia symptoms is associated with risk of fibromyalgia in a dose-dependent way and whether lifestyle factors can change this association.

“Some evidence indicates that leisure time physical activity and maintenance of normal body weight to some extent can reduce the adverse effect of sleep problems on risk of chronic pain in the low back and neck/shoulders,” the authors wrote.

A Norwegian team of investigators sought to study the association between insomnia symptoms and risk of self-reported fibromyalgia in women, and to explore whether leisure time physical activity and body mass index affect this association.

To do so, they used data from a longitudinal population health study called Norwegian Nord-Trøndelag Health Study (also known as the HUNT study), which gathered questionnaire-based information on lifestyle and health-related factors.

Scientists focused on data collected from 1995–1997 (baseline, i.e. study’s beginning) and 2006–2008 (follow-up). Data from 14,172 women who reported to be free from fibromyalgia between 1995 and 1997 was analyzed and the risk for self-reported fibromyalgia was estimated.

Participants were considered to have insomnia symptoms if they answered “often” or “almost every night” to the questions:

• “During the last month, have you had problems falling asleep?”
• “During the last month, did you ever wake up too early, not being able to fall asleep again?”
• “During the last year, have you been troubled by insomnia to such a degree that it influenced your work ability?”

About 20% (2,397) of the women had one or more insomnia symptoms. The ones with insomnia symptoms had a mean age of 47 years, while the women without such complaints were around 43.5 years old.

During the study period, 466 new cases of fibromyalgia were reported. The increasing number of insomnia symptoms was found to be positively correlated with the risk of developing fibromyalgia. More specifically, women who reported one, two, or three symptoms had risk ratios of fibromyalgia of 1.39, 1.86, and 2.66, respectively.

In women with one or more insomnia symptoms, low physical activity was associated with a higher risk of fibromyalgia (1.90), while frequent physical activity appeared to reduce such risk (1.55).

Although scientists found no synergistic effect between insomnia symptoms and body mass index, women with excess weight and one or more insomnia symptoms had a risk ratio of 2.35 and obese subjects with the same number of disturbed sleep complaints had a fibromyalgia risk of 2.18, in comparison with the reference group of normal weight participants without insomnia symptoms (risk ratio of 1).

“Leisure time physical activity may modify some of the adverse effect of insomnia symptoms on risk of fibromyalgia,” the researchers said. “These findings indicate that preventing sleep problems and promoting a healthy active lifestyle are important to reduce the incidence of fibromyalgia.”