medwireNews: Findings from a longitudinal study suggest that obese people have an elevated risk for developing psoriatic arthritis (PsA).
Moreover, individuals taking part in high levels of physical activity have a reduced risk for PsA compared with those who are inactive, regardless of BMI, report Ruth Stoklund Thomsen (Norwegian University of Science and Technology, Trondheim) and fellow researchers.
“[O]ur 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,” they write in Arthritis Care & Research.
The analysis included 36,626 people from the Norwegian population-based HUNT study who were free form PsA in 1995–1997 and followed up until 2006–2008. Average BMI at baseline ranged from 25.1 to 27.3 kg/m2 among men and women falling into different categories of physical activity, while average waist circumference ranged from 77.3 to 93.2 cm.
Over the follow-up period, 185 participants developed PsA, 59% of whom were women.
Thomsen and colleagues found that each standard deviation increase in BMI – 4.2 kg/m2 in women and 3.5 kg/m2 in men – was associated with a significant 1.40-fold increase in the risk for PsA after adjustment for sex, age, education level, and smoking status.
Similarly, each standard deviation increase in waist circumference (10.8 cm in women and 8.6 cm in men) and waist-to-hip ratio (0.06 in women and 0.05 in men) was associated with a significantly increased risk, with adjusted hazard ratios (HRs) of 1.48 and 1.39, respectively.
When participants were categorized according to obesity status, those with a BMI of 30 kg/m2 or higher had a greater than twofold higher risk for PsA than those with a BMI of 18.5–24.9 kg/m2 (adjusted HR=2.63), while those with a high waist circumference according to World Health Organization cutoffs (≥81 cm and ≥95 cm for women and men, respectively) had a 1.75-fold greater risk than those with smaller measurements.
And when physical activity was taken into account, overweight and obese individuals (BMI≥25 kg/m2) classified as inactive or having low levels of physical activity (<3 hours of light and no hard leisure-time activity per week) were more than twice as likely as people of normal bodyweight with high levels of physical activity (any light and ≥1 hour of hard activity per week) to develop PsA, with an adjusted HR of 2.06.
There was also a trend for increased PsA risk among people in the overweight/obese group with high levels of physical activity and those in the normal bodyweight category with low levels of physical activity relative to those with normal bodyweight and high levels of physical activity, but these associations did not reach statistical significance.
“Although there was no clear evidence of a synergistic effect of physical activity and adiposity on PsA risk, the results suggest that the adverse effect of adiposity was somewhat lower among the most physically active participants,” say the researchers.
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Arthritis Care Res 2019; doi:10.1002/acr.24121