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: We hypothesised that individuals with an unhealthy diet have increased risk of prevalent and incident psoriasis.
Methods: We included 105,332 adults from the Copenhagen General Population Study, who were invited between 2003 and 2015. Response-rate was 43%. An unhealthy versus healthy diet was defined according to adherence to general national dietary guidelines. The participants were grouped into low, intermediate, and high adherence to general national dietary guidelines based on information from a food frequency questionnaire. Identification of psoriasis was made using ICD 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 non-adherence 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 non-adherence 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.
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