Adiposity and physical activity as risk factors for developing psoriatic arthritis. Longitudinal data from the HUNT study.

Abstract

OBJECTIVE\nAdiposity is prevalent among patients with psoriatic arthritis (PsA). However, the temporal relation is unclear. We investigated whether adiposity and body fat distribution may be related to the risk of developing PsA, and whether physical activity could modify the possible risk.\n\n\nMETHODS\nWe included 36,626 women and men from the Norwegian HUNT Study without diagnosed PsA at baseline in 1995-97. Cox regression was used to estimate adjusted hazard ratios (HRs) with 95% confidence intervals (CIs) of incident PsA at follow-up in 2006-08.\n\n\nRESULTS\nDuring follow-up, 185 new cases of PsA were reported. One standard deviation increases in BMI (4.2 and 3.5 kg/m2 for women and men) and waist circumference (10.8 and 8.6 cm) were associated with HRs of 1.40 (95% CI 1.24-1.58) and 1.48 (1.31-1.68), respectively. Obese individuals had a HR of 2.46 (1.65-3.68) and overweight 1.41 (1.00-1.99) compared to normal weight individuals. Comparing extreme quartiles of waist circumference gave a HR of 2.63 (1.73-3.99). In analyzes of combined effects using BMI<25 kg/m2 and high physical activity as reference, BMI≥25 kg/m2 was associated with HRs of 2.06 (1.18-3.58) and 1.53 (0.80-2.91) among those with low and high physical activity levels, respectively. Corresponding HRs for high waist circumference and physical activity were 2.25 (1.40-1.63) and 1.85 (0.95-3.50).\n\n\nCONCLUSION\nThe results suggest that adiposity, and particularly central obesity, is associated with increased risk of incident PsA. Although there was no clear modifying effect of physical activity, high levels of physical activity reduced the risk of PsA, regardless of BMI.