Incidence and determinants of chronic pruritus: a population-based cohort study.

Epidemiological data on chronic pruritus (> 6 weeks) in the general population are sparse. We aimed to provide data on the incidence and prevalence of chronic pruritus, and identify its determinants based on cross-sectional and longitudinal analyses. A cohort of 1,190 participants from a cross-sectional baseline-study (response rate: 57.8%) was followed up after one year. The questionnaire assessed occurrence of chronic pruritus, medical, lifestyle and psychosocial variables. Incident chronic pruritus was defined as reported chronic pruritus at follow-up in those subjects free-of-the-symptom at baseline. Cross-sectional analyses of data from the follow-up assessments addressed potential associations of medical, lifestyle and psychosocial factors with prevalent chronic pruritus. Longitudinal analyses examined sociodemographic factors as potential predictors of incident chronic pruritus. The follow-up response rate was 83.1%. The mean age of subjects was 56 years, and 58% were female. The 12-month cumulative-incidence equalled 7.0% (95% confidence interval (95% CI) 5.2-9.2%. Lifetime prevalence was 25.5% (95% CI 21.8-27.8%). Incidence was significantly associated with age. Determinants of prevalent chronic pruritus in multi-variable analyses were: liver disease, asthma, eczema and dry skin within the medical domain, an elevated body mass index within the lifestyle domain and higher anxiety scores within the psychosocial domain. Findings suggest a considerable 12-month incidence and lifetime prevalence and provide important directions for future research.