Adherence to general national dietary guidelines and risk of psoriasis: results from a general population study of 105 332 individuals

Background It is unknown if an unhealthy diet can affect the risk of developing psoriasis.Objectives To test the hypothesis that individuals with an unhealthy diet have an increased risk of prevalent and incident psoriasis.Methods We included 105 332 adults from the Copenhagen General Population Study, who were invited to participate between 2003 and 2015. The response rate was 43%. An unhealthy vs. healthy diet was defined according to adherence to general national dietary guidelines. The participants were grouped into three groups: low, intermediate and high adherence to general national dietary guidelines; this was based on information from a food frequency questionnaire. Identification of psoriasis was made using International Classification of Diseases codes.Results Of the 105 332 individuals, 580 had a diagnosis of psoriasis at the time of enrolment and 640 received a diagnosis during the median follow-up of 9 years. Risk of prevalent psoriasis increased according to nonadherence to general national dietary guidelines in a stepwise manner with an age- and sex-adjusted odds ratio of 1.70 (95% confidence interval 1.26-2.30) in individuals with low vs. high adherence to dietary guidelines. Results were similar in a multivariable-adjusted model. Prospective analyses adjusted for age and sex showed a weak association between nonadherence to dietary guidelines and risk of incident psoriasis (P for trend 0.04). This association disappeared, when adjusting for multiple confounders (P for trend 0.50).Conclusions Although individuals with psoriasis have an unhealthier diet, diet alone does not appear to independently increase the risk of developing psoriasis. Graphical Abstract In this study we found that individuals with psoriasis had an unhealthier diet compared with individuals without psoriasis. However, an unhealthy diet alone does not appear to independently increase the risk of incident psoriasis.