Risk of fibromyalgia at 11-year follow-up associated with baseline insomnia symptoms
| Insomnia symptoms | No. of persons | No. of cases | Age-adjusted RR* | Multi-adjusted RR† (95% CI) |
| No. of symptoms‡ | ||||
| 0 | 11 775 | 334 | 1.00 | 1.00 (reference) |
| 1 | 1566 | 71 | 1.60 | 1.39 (1.08 to 1.80) |
| 2 | 612 | 40 | 2.36 | 1.86 (1.33 to 2.59) |
| 3 | 219 | 21 | 3.53 | 2.66 (1.75 to 4.06) |
| Insomnia symptoms§ | ||||
| No | 11 775 | 334 | 1.00 | 1.00 (reference) |
| Yes | 2397 | 132 | 1.96 | 1.64 (1.34 to 2.02) |
*Adjusted for age (20–29, 30–39, 40–49, 50–59, 60–69 and ≥70 years).
†Adjusted for age (20–29, 30–39, 40–49, 50–59, 60–69 and ≥70 years), body mass index (18.5–24.9, 25.0–29.9 and ≥30 kg/m2), leisure time physical activity (high activity, moderate activity and low activity), education (primary school, high school, college ≤4 years, college ≥4 years and unknown), The Hospital Anxiety and Depression Scale (no depression and no anxiety, depression and/or anxiety, and unknown) and smoking (never, former, current smoker and unknown).
‡No. of symptoms were defined by adding up those who responded ‘Often/always’ on the questions about ‘Problems falling asleep’ and ‘Waking up too early’ and ‘Yes’ on the question about ‘Impaired work ability due to sleep problems’.
§Participants were classified with insomnia symptoms if they answered ‘Often/always’ on at least one of the questions about ‘Problems falling asleep’ and ‘Waking up too early’ or ‘Yes’ on the question about ‘Impaired work ability due to sleep problems’.
RR, risk ratio.