Background Several studies have investigated the association between overweight and the development of rheumatoid arthritis (RA) and have come out with conflicting results. Body Mass Index (BMI) has been the preferred surrogate measure for overweight in these studies. However, BMI correlates only modestly with total amount of body fat and does not reflect fat distribution.

Objectives To investigate the association between BMI, waist circumference, bio-impedance-derived total body fat percentage and the incidence of RA.

Methods A population-based cohort study conducted within the Danish Diet, Cancer and Health cohort, which included individuals aged 50 to 64 years at the recruitment in the period between 1993 and 1997. Body fat composition measurements and data on lifestyle factors were collected at the enrolment into the cohort. The participants who subsequently developed RA were identified via linkage to The Danish National Patient Registry. The participants were followed until development of RA, death, loss to follow-up or October 2016, whichever came first. Data were analyzed by Cox proportional hazards regression model with delayed entry and age as the underlying time variable. Analyses were stratified by gender. Cox regression analyses with restricted cubic spline were carried out to elucidate the dose-response association between anthropometric measures and risk of RA. Smoking, socio-economic status, alcohol consumption, physical activity and intake of n-3 fatty acids were included in multivariate analyses as potential confounders.

Results Data were available on 54 284 subjects (52% female). During follow-up (median 21 years), 283 women and 110 men developed RA. The median (IQR) time to onset of RA was 7 (4–11) years. The adjusted hazard ratio's (HR) for developing RA are presented in Table 1. Restricted cubic spline analysis of body fat percentage displayed a positive slope in women (Image). There was no linear association between amount of fat and incidence of RA among men.

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Conclusions Overweight and obesity, defined by BMI, abdominal obesity and higher body fat percentage, especially above 30%, were in women associated with a higher risk for the development of RA. In men the associations were not consistent.

Acknowledgements The Danish Rheumatism Association, The Danish Heart Foundation, Central Denmark Region, North Denmark Regional Hospital, Scandinavian Rheumatology Research Foundation

Disclosure of Interest None declared