The Mediterranean diet has been reported to be associated with a significant reduction in risk of noncommunicable diseases. We undertook this study to assess the relationship between adherence to the Mediterranean diet and the risk of rheumatoid arthritis (RA), especially in high-risk individuals.
The E3N study (Etude Epidémiologique Auprès des Femmes de la Mutuelle Générale de l'Education Nationale) is a French prospective cohort study that has included 98,995 women since 1990. Dietary data were collected via a validated food frequency questionnaire in 1993. Adherence to the Mediterranean diet was assessed using a 9-unit dietary score evaluating consumption of vegetables, legumes, cereal products, fish, meat, dairy products, olive oil, and alcohol. Hazard ratios (HRs) and 95% confidence intervals (95% CIs) for incident RA were estimated using Cox proportional hazards regression models adjusted for age and the main potential confounders, including smoking.
Among 62,629 women, we identified 480 incident cases of RA. In the entire study population, the Mediterranean diet adherence score was not associated with RA risk (HR 0.86 [95% CI 0.67-1.09] for high score versus low score; P for trend = 0.09); however, among ever-smokers, a higher score was associated with a decreased risk of RA (HR 0.91 [95% CI 0.84-0.99] for 1-point increase in score; P = 0.03). In ever-smokers, the absolute risks of RA in those with high scores and those with low scores were 38.3 and 51.5 per 100,000 person-years, respectively, compared to 35.8 per 100,000 person-years in never-smokers with high Mediterranean diet scores.
Our results suggest that adherence to the Mediterranean diet could reduce the high risk of RA among ever-smoking women. Our results must be confirmed in future research.