Background Psoriasis is a common chronic inflammatory skin disorder. Higher adiposity may increase the risk of psoriasis, but prospective data on this association are scarce. One prospective study showed that increased adiposity increased the risk of incident psoriasis in younger women, but no data are available in older women. Methods We prospectively examined the associations between body mass index (BMI), weight change, waist and hip circumference and risk of incident psoriasis in 67,300 women over a 12-year period (1996-2008) in the Nurses’ Health Study. The primary outcome was self-reported, physician-diagnosed psoriasis. Results During the 12 years of follow-up, there were a total of 809 incident psoriasis cases. There was a graded positive association between BMI (both baseline and updated) and the risk of psoriasis (both P values for trend <0.0001). Compared to women with updated BMI of <25, the multivariate RRs (relative risks) of incident psoriasis were 1.21 (95% CI, 1.03-1.43) for a BMI of 25.0 to 29.9, 1.63 (95% CI, 1.33-2.00) for a BMI of 30.0 to 34.9, and 2.03 (95% CI, 1.58-2.61) for a BMI of 35.0 or greater. Higher waist circumference, hip circumference, and waist-hip ratio were associated with a higher risk of incident psoriasis, but became non-significant after additionally adjusting for BMI. The BMI at age of 18 years was not associated with the risk of psoriasis. Weight gain since the age of 18 years was associated with an increased risk of psoriasis and RR of 10 lb gain was 1.08 (95% CI, 1.06-1.11; p<0.0001). Conclusion This large prospective study indicates that higher BMI and weight gain are risk factors for incident psoriasis in older US women.

Summary Background Psoriasis is a common, chronic and inflammatory disease of the skin, which has been associated with depression in cross-sectional studies with limited adjustment for confounders. Objectives In this prospective cohort study, we investigated the risk of incident depression among individuals with psoriasis and psoriatic arthritis (PsA). Methods We included 50 750 US female nurses from the Nurses’ Health Study who were free of depression at baseline in 2000. Those participants who had ever self-reported clinician-diagnosed depression or regular use of antidepressants, or had a Mental Health Inventory score of ≤ 52 were excluded. In 2008, we retrospectively asked participants if they had ever received a physician’s diagnosis of psoriasis or PsA. We defined depression as self-report of clinician-diagnosed depression or regular use of antidepressant medication. Time-dependent Cox proportional hazard models were used to estimate age and multivariate-adjusted relative risks (RRs) of clinical depression. Results After adjusting for covariates including body mass index, physical activity, smoking and the presence of major chronic conditions, the multivariate-adjusted RRs of clinical depression were 1.29 [95% confidence interval (CI) 1.10–1.52] for women with psoriasis and 1.52 (95% CI 1.06–2.19) for women with psoriasis and concomitant PsA, compared with women without psoriasis. Conclusions We found an increased risk of depression in US women with psoriasis compared with those without psoriasis. This risk was higher in those who reported concomitant PsA. Future studies are needed to confirm these findings in other populations and to identify pathophysiological mechanisms linking psoriasis to depression.

Summary Background We present the largest set of US prevalence data for psoriasis to date, obtained from three prospective cohort studies describing validated clinical phenotypes of psoriasis, including novel data about the prevalence of inverse (intertriginous) psoriasis in these groups. Nonplaque psoriasis phenotypes have been largely unmeasured in observational and interventional studies, and this has led to an under-recognition of this aspect of psoriatic disease. Aim To describe the prevalence of nonplaque psoriasis phenotypes in a large prospective cohort. Methods We included 3179 women and 646 menin the analysis. Participants in the Nurses Health Study and Health Professionals Follow-up Study with physician-diagnosed psoriasis completed a validated, self-administered questionnaire to assess plaque and nonplaque subsets of psoriasis. Results Psoriasis phenotypes were as follows: plaque 55%, scalp 52%, palmar–plantar 14%, nail 23% and inverse 21% in the Nurses Health Study (NHS) (n = 1604); plaque 60%, scalp 56%, palmar–plantar 16%, nail 27% and inverse 24% in the second NHS study (NHS II) (n = 1575); and plaque 55%, scalp 45%, palmar–plantar 12%, nail 27% and inverse 30% in the Health Professionals Follow-up Study (n = 646). Scalp, nail, palmar–plantar and inverse disease represent highly prevalent phenotypes of psoriasis in the USA. Conclusion Scalp, nail, palmar–plantar and inverse disease represent highly prevalent phenotypes of psoriasis.