From the Journals

Evidence builds for effects of obesity, low physical activity on development of psoriatic arthritis



A new Norwegian study has identified a high body mass index and lower levels of physical activity as modifiable risk factors for developing psoriatic arthritis (PsA).

“Our study adds to the growing evidence that the risk of PsA is modifiable and highlights the importance of preventive work against obesity as well as encouraging physical activity in order to reduce the incidence of PsA,” wrote Ruth S. Thomsen, MD, of the Norwegian University of Science and Technology, and coauthors. The study was published in Arthritis Care & Research.

To determine the impact that adiposity and body fat distribution have on developing PsA, the researchers analyzed data from 36,626 women and men who participated in two surveys from the longitudinal, population-based Norwegian HUNT Study. All participants did not have diagnosed PsA at baseline in 1995-1997. Variables used in statistical analysis included calculated baseline BMI, waist circumference, waist-hip ratio, and level of physical activity.

Between baseline and follow-up in 2012, 185 new cases of PsA were reported. One standard deviation increase in BMI (4.2 kg/m2 for women, 3.5 kg/m2 for men) and waist circumstance (10.8 cm for women, 8.6 cm for men) was associated with adjusted hazard ratios of 1.40 (95% confidence interval, 1.24-1.58) and 1.48 (95% CI, 1.31-1.68), accordingly. Obese individuals – defined as BMI of 30 kg/m2 or higher – had an adjusted HR of 2.46 (95% CI, 1.65-3.68) when compared with individuals at normal weight.

Compared to individuals with BMI less than 25 kg/m2 and a high level of physical activity, individuals with BMI at 25 kg/m2 or higher and any lower level of physical activity had an adjusted HR of 2.06 (95% CI, 1.18-3.58). In addition, individuals with a high waist circumference – defined as 81 cm or more in women and 95 cm or more in men – and low physical activity had an adjusted HR of 2.22 (95% CI, 1.37-3.58) in comparison to those with a high waist circumference and high physical activity (adjusted HR, 1.84; 95% CI, 0.97-3.47). Physical activity level was considered low with less than 3 hours of light physical activity and no hard physical activity per week and high with any amount of light activity plus 1 or more hours of hard physical activity.

The authors acknowledged the study’s potential limitations, including the requirement for participants to complete the final two HUNT study surveys and the use of stricter criteria than usual in validating PsA diagnoses.

The study was partially funded by a grant Dr. Thomsen received from the Norwegian Extra Foundation for Health and Rehabilitation. The authors reported no conflicts of interest.

SOURCE: Thomsen RS et al. Arthritis Care Res. 2019 Dec 7. doi: 10.1002/acr.24121.

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