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

Abstract 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.