The role of lifestyle factors in the association between education and self-reported fibromyalgia: a mediation analysis.

BACKGROUND: Socioeconomic status as measured by education, income, or occupation, has been associated with fibromyalgia but the underlying mechanism and the role of lifestyle factors are unclear. Thus, we examine the role of modifiable lifestyle factors (body mass index, physical activity, alcohol consumption and smoking) in the association between education and self-reported fibromyalgia. METHODS: We used data from 74,157 participants in the population-based prospective Norwegian Women and Cancer (NOWAC) study. Socioeconomic position, operationalized as years of educational attainment, and lifestyle factors were assessed via self-reported questionnaires. Multiple mediation analysis was used to decompose total effects into direct and indirect effects. Estimates were reported as hazard ratios (HRs) with 95% confidence intervals (CIs). RESULTS: The cumulative incidence of fibromyalgia was 3.2% after a median follow up time of 13 years. Fibromyalgia was inversely associated with years of educational attainment for ≤ 9 years (HR = 2.56; 95% CI 2.32-2.91) and for 10-12 years (HR = 1.84; 95% CI 1.72-2.02), compared with ≥ 13 years of education. Overall, all lifestyle factors together jointly mediated 17.3% (95% CI 14.3-21.6) and 14.1% (95% CI 11.3-18.9) of the total effect for ≤ 9 years and 10-12 years of education, respectively. Smoking and alcohol consumption contributed the most to the proportion mediated, for ≤ 9 years (5.0% and 7.0%) and 10-12 years (5.6% and 4.5%) of education. CONCLUSION: The association between education and self-reported fibromyalgia was partly explained through lifestyle factors, mainly smoking and alcohol consumption.

Lifestyle risk factors of self-reported fibromyalgia in the Norwegian Women and Cancer (NOWAC) study.

BACKGROUND: While the aetiology of fibromyalgia syndrome (FM) remains unknown, lifestyle factors have been linked to the disorder. However, there are few studies on the association between lifestyle factors and FM, thus we examine the risk of self-reported fibromyalgia given selected lifestyle factors. METHODS: We used data from 75,485 participants in the Norwegian Women and Cancer study. Information on FM and the lifestyle factors body mass index (BMI), physical activity level, smoking status/intensity, and alcohol consumption were obtained from baseline and follow-up questionnaires. We used Cox proportional hazards model to calculate hazard ratios (HRs) with 95% confidence intervals (CIs). RESULTS: After a median follow-up time of 10 years, we observed 2,248 cases of self-reported fibromyalgia. Overweight (BMI 25-29.9 kg/m2) and obese (BMI ≥ 30 kg/m2) women had a relative risk of 1.34 (95% CI 1.21-1.47) and 1.62 (95% CI 1.41-1.87), respectively, compared to women with normal weight (BMI 18.5-24.9 kg/m2). Very low physical activity level (1-2) was associated with a 31% higher risk of self-reported fibromyalgia (HR 1.31, 95% CI 1.09-1.57) when compared to moderate physical activity level (5-6). There was a strong dose-response relationship between smoking status/intensity and self-reported fibromyalgia (p for trend < 0.001). Compared with moderate alcohol consumption (4.0-10 g/day), the risk of self-reported FM was 72% (HR 1.72; 95% CI 1.45-2.03) higher among teetotallers, and 38% (HR 1.38, 95% CI 1.23-1.54) higher among those with low consumption (0.1-3.9 g/day). CONCLUSIONS: Overweight and obesity, very low physical activity level, smoking, and alcohol consumption were associated with an increased risk of self-reported FM.