Risk of psoriasis according to body mass index: A retrospective cohort analysis

Background Psoriasis has been linked to obesity, although data on the incidence of psoriasis according to body mass index (BMI) are limited. Objective To compare incidence of psoriasis among patients stratified by BMI category (normal or underweight, overweight, obese class 1, obese class 2/3). Methods Retrospective cohort analysis of a demographically heterogeneous sample of over 1.5 million patients in the United States between January 1, 2008 and September 9, 2019. Results Crude incidence of psoriasis per 10,000 person-years was 9.5 (95% confidence interval [CI], 9.1-10.0) among normal or underweight patients, 11.9 (95% CI, 11.4-12.4) among overweight patients, 14.2 (95% CI, 13.6-14.9) among obese class 1 patients, and 17.4 (95% CI, 16.6-18.2) among obese class 2/3 patients. Compared to patients with BMI < 25.0, those who were overweight (adjusted hazard ratio, 1.19; 95% CI, 1.12-1.27; P < .001), obese class 1 (adjusted hazard ratio, 1.43; CI, 1.34-1.53; P < .001) and obese class 2/3 (adjusted hazard ratio, 1.83; CI, 1.71-1.95; P < .001) significantly greater risks for developing psoriasis. Limitations Influence of obesity on psoriasis severity could not be measured. Conclusion BMI independently influences the development of psoriasis. There appears to be a graded association between BMI and risk of psoriasis. Psoriasis has been linked to obesity, although data on the incidence of psoriasis according to body mass index (BMI) are limited. To compare incidence of psoriasis among patients stratified by BMI category (normal or underweight, overweight, obese class 1, obese class 2/3). Retrospective cohort analysis of a demographically heterogeneous sample of over 1.5 million patients in the United States between January 1, 2008 and September 9, 2019. Crude incidence of psoriasis per 10,000 person-years was 9.5 (95% confidence interval [CI], 9.1-10.0) among normal or underweight patients, 11.9 (95% CI, 11.4-12.4) among overweight patients, 14.2 (95% CI, 13.6-14.9) among obese class 1 patients, and 17.4 (95% CI, 16.6-18.2) among obese class 2/3 patients. Compared to patients with BMI < 25.0, those who were overweight (adjusted hazard ratio, 1.19; 95% CI, 1.12-1.27; P < .001), obese class 1 (adjusted hazard ratio, 1.43; CI, 1.34-1.53; P < .001) and obese class 2/3 (adjusted hazard ratio, 1.83; CI, 1.71-1.95; P < .001) significantly greater risks for developing psoriasis. Influence of obesity on psoriasis severity could not be measured. BMI independently influences the development of psoriasis. There appears to be a graded association between BMI and risk of psoriasis.