Combined effects of HLA-Cw6, body mass index and waist-hip ratio on psoriasis vulgaris in Chinese Han population

Background: Psoriasis is a chronic inflammatory skin disease associated with an HLA-Cw6 allele. Higher waist-hip ratio (WHR) and body mass index (BMI) may increase the risk of psoriasis vulgaris, but, to our knowledge, no evidence of the combined effects of HLA-Cw6 and BMI, WHR are available. Objectives: To evaluate the combined effect of HLA-Cw6, BMI and WHR on psoriasis vaulgaris. Methods: The data of 466 patients and 177 controls were investigated and analyzed by a hospital-based case-control study and non-condition logistic regress model. Results: There was a graded positive association of WHIR and BMI with psoriasis vulgaris. Compared with a WHR of 0.80 or less than 0.80, the odds ratio (OR) was 2.36 (p < 0.01) for WHIR 0.80-0.85, and 2.74 (p < 0.01) for WHR greater than 0.85. Compared with subjects with a BMI of 20 or less than 20, the multivariate OR of psoriasis were 1.20 (p > 0.05) for a BMI of 20-25, 1.84 (p < 0.05) for a BMI of more than 25 corresponding overweight (p for trend, <0.01). We found not only the risk of psoriasis for the individual with HLA-Cw6(+) was 8.33 times greater than that for individual with HLA-Cw6(-) but also the risk increased approximately 35 times in individuals with HLA-Cw6(+) and a overweight as compared with one with HLA-Cw6- and a non-overweight, and 17-fold when the individuals with HLA-Cw6(+) and a WHR of more than 0.80 were compared with individuals with HLA-Cw6(-) and a WHR of 0.80 or less than 0.80, displaying the combined effect of HLA-Cw6, BMI and WHR (all p < 001). Conclusion: This study suggested that HLA-Cw6, overweight and higher waist-hip ratio are material risk factors of psoriasis vulgaris, specially the combined effects of HLA-Cw6 and BMI, WHR on psoriasis vulgaris in Chinese population. (C) 2008 Published by Elsevier Ireland Ltd on behalf of Japanese Society for Investigative Dermatology.