Obesity, central adiposity double risk of developing psoriasis
Individuals with obesity and high abdominal fat mass appear to have a twofold increased risk of developing psoriasis, as shown in a study. Long-term weight gain of ≥10 kg is also associated with a substantially increased risk.
Results showed that of the 33,734 individuals (mean age 47 years; 55 percent female) in the population-based Nord-Trøndelag Health Study (ie, HUNT) followed for 10 years, 369 developed psoriasis. There was a positive association between the risk of the chronic autoimmune disease and all body composition measures.
In multivariable Cox regression models, a one-SD increase in body mass index (3.81 kg/m2), waist circumference (11.14 cm), and waist-hip ratio (0.08) respectively increased the risk of incident psoriasis by 1.22 (95 percent CI, 1.11–1.34), 1.26 (1.15–1.39), and 1.18 (1.07–1.31) times. [J Investig Dermatol 2017;137:2484–2490]
Relative to normal-weight individuals, those with obesity were nearly twice as likely to have incident psoriasis (relative risk [RR], 1.87; 1.38–2.52). When comparing extreme categories of waist circumference, the fourth vs the first quartile was likewise associated with a twofold increased risk of developing the autoimmune disease (RR, 1.95; 1.46–2.61).
Analysis in the subgroup of individuals with 10-year data on weight change showed that the risk increased by 20 percent (RR, 1.20; 1.07–1.35) for every one-SD (5.96 kg) increase in weight change and by 72 percent among those with a long-term weight gain of ≥10 kg (RR, 1.72; 1.15–2.58).
“In conclusion, our study supports former findings that body weight is associated with psoriasis risk, and we found a consistent dose-response relationship across multiple obesity-related measurements,” the investigators said, noting that although psoriasis has been extensively studied in relation to obesity, the present study used objectively measured rather than self-reported weight.
“Strong associations between waist circumference and psoriasis risk could indicate that central adiposity plays an important role in disease development,” they added. “There was suggestive evidence that a weight decrease was associated with reduced risk of psoriasis, but low statistical precision calls for cautious interpretation of these results.”
Resident macrophages within adipose tissue may explain why obesity could induce psoriasis. These macrophages contribute to the production of psoriasis-signature cytokines such as IL-6 and tumour necrosis factor-α, which are also reported to lead to insulin resistance and altered lipid metabolism, hypertension, and enhanced risk of cardiovascular disease. A common genetic link between psoriasis and obesity is also a possible mechanism. [Exp Rev Clin Immunol 2016;12:1–10; JAMA Dermatol 2016;152:761–767]
“From a public health perspective, nearly a quarter of psoriasis cases could be attributed to overweight or obesity if the estimated associations [in the current study] reflect causal relations,” the investigators said.