Increased sodium consumption is associated with psoriasis: A population‐based cohort study

BACKGROUND: Sodium is stored in skin and may trigger or perpetuate autoimmune diseases including psoriasis. One previous study found skin sodium was elevated in a small group of patients with severe psoriasis compared to healthy controls, but the relationship between sodium intake and psoriasis within a population has not been investigated. OBJECTIVES: To identify whether dietary sodium intake is associated with psoriasis and whether there are subgroups of individuals more likely to have salt-sensitive psoriasis. METHODS: This cross-sectional, population-based study evaluated a UK Biobank cohort of nearly 500,000 participants in the 2006-2010 period and a US-based National Health and Nutrition Examination Survey (NHANES) validation cohort of 2393 participants in the 2003-2004 period. Dietary sodium intake, the exposure, was estimated using urine biomarkers and the previously validated INTERSALT equation. Psoriasis outcome was assessed by the presence of ICD-10 code L40. RESULTS: In the UK Biobank, of the 468,913 included participants, 54% were female and mean (standard deviation) age at recruitment was 57 (8) years. Multivariable logistic regression models revealed that every 1 g increase in estimated 24-h urine sodium was associated with an 18% increase in odds of psoriasis (OR 1.18, 95% CI: 1.14-1.21) after adjustment for sex, age, race/ethnicity, education and socioeconomic status. There was no consistent evidence of large effect modification by age, sex, race/ethnicity, polygenic risk score for psoriasis or those with a history of hypertension, chronic renal failure or type 2 diabetes mellitus. In NHANES, each additional gram of self-reported dietary sodium intake was also associated with increased odds of examination-confirmed psoriasis (OR: 1.47, 95% CI: 1.19-1.83). CONCLUSIONS: Increased sodium intake was associated with psoriasis in two population-based cohorts; future clinical trials could investigate whether decreasing sodium intake improves psoriasis.