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Psoriasis prevalence has long been considered to be 2-4% in the United States (US). Recently, prevalence rates of 0.5-0.6% were reported in Medicare patients and 0.128% in commercially insured children. We investigated psoriasis prevalence among commercially insured individuals younger than 65 years. The Truven Health Analytics MarketScan Commercial Claims and Encounters databases, which includes beneficiaries of employer-based commercial insurance in the US, was interrogated for continuously enrolled beneficiaries from 2011-2017. Psoriasis cases were identified using >=1 or >=2 inpatient or outpatient claims by any physician (ICD-9-CM code 696.1; ICD-10-CM codes L40.0-L40.4, L40.8, L40.9). Annual prevalence and 95% confidence intervals (CI) were calculated for each year separately. Information on gender and age range was also collected. Defining psoriasis as >=1 claim yielded a prevalence of 0.529% (95% CI 0.526-0.531) in 2011 and 0.718% (95% CI 0.714-0.721) in 2017. Women (51.7-53%) were slightly more represented than men (48.3-47%). Prevalence rose in the 18-34 years and 45-54 years age groups, reflecting a bimodal distribution of onset of psoriasis. When using >=2 claims of psoriasis as the definition, the prevalence fell to 0.220% (95% CI 0.219-0.222) to 0.329% (95% CI 0.326-0.331) during the study period. This study suggests that psoriasis is possibly up to 4-fold less prevalent than previously believed with a prevalence of 0.5-0.7% using >=1 claim of psoriasis as our criterion. When using 2 claims for psoriasis, a more clinically vigorous case definition, prevalence dropped to 0.2-0.3%. This replicates observations of previous studies and reflects the greater positive predictive value of using multiple claims for psoriasis as compared to one claim. Limitations of our study include diagnosis misclassification and the restriction to commercial insurance beneficiaries. Given the effects of psoriasis on quality of life, comorbid conditions, and health care utilization, a re-appraisal of the prevalence of psoriasis in the US is a necessary consideration.
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The field of contact dermatitis is constantly evolving. Trends in irritant and allergic contact dermatitis are shaped by the introduction of new chemicals, revival of older allergens, industrial practices, and consumer behaviors. This article discusses the most noteworthy trends within the field, organized by allergen category, with particular attention to newer and/or controversial allergens.