Long term alcohol intake and risk of rheumatoid arthritis in women: a population based cohort study

Objective To analyse the association between alcohol intake and incidence of rheumatoid arthritis in women. Design Prospective cohort study with repeated measurements. Setting The Swedish Mammography Cohort, a population based cohort from central Sweden. Participants 34 141 women born between 1914 and 1948, followed up from 1 January 2003 to 31 December 2009. Main outcome measures Newly diagnosed cases of rheumatoid arthritis identified by linkage with two Swedish national registers. Data on alcohol consumption were collected in 1987 and 1997. Results During the follow-up period (226 032 person years), 197 incident cases of rheumatoid arthritis were identified. There was a statistically significant 37% decrease in risk of rheumatoid arthritis among women who drank >4 glasses of alcohol (1 glass = 15 g of ethanol) per week compared with women who drank <1 glass per week or who never drank alcohol (relative risk 0.63 (95% confidence interval 0.42 to 0.96), P=0.04). Drinking of all types of alcohol (beer, wine, and liquor) was non-significantly inversely associated with the risk of rheumatoid arthritis. Analysis of long term alcohol consumption showed that women who reported drinking >3 glasses of alcohol per week in both 1987 and 1997 had a 52% decreased risk of rheumatoid arthritis compared with those who never drank (relative risk 0.48 (0.24 to 0.98)). Conclusion Moderate consumption of alcohol is associated with reduced risk of rheumatoid arthritis.