In the study (.pdf), Norwegian researchers recruited 12,350 women aged 20 and older and followed them for a 10-year period. Participants were part of a large nationwide health survey that involved completing questionnaires and physical exams first between 1984 and 1986 and again between 1995 and 1997. None of the volunteers had chronic musculoskeletal pain upon enrolling in the study. Medpage Today reports:
A total of 327 women reported having been given a diagnosis of fibromyalgia at follow-up, which represented an incidence proportion of 2.6%.
Women ages 20 to 44 had an incidence proportion of 3.2%; the incidence proportion for those 45 and older was 1.7%.
In analyses that adjusted for smoking, education, physical exercise, body mass index, and education, the researchers found that women 45 and older who had frequent sleep difficulties had a rate ratio for fibromyalgia of 5.41, while the younger cohort had a rate ratio of 2.98.
[Researchers] then compared the 3,949 women who reported sleep problems of any frequency with the 8,401 who had no sleep disturbances, and found a rate ratio for fibromyalgia of 2.10