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.