Sodium in Patients’ Diets Linked to Increased Atopic Dermatitis Severity

Brenda M. Chiang, MS

Credit: Abuabara Research Group

Sodium intake through diet is associated with prevalent and active atopic dermatitis (AD) as well as increased disease severity, according to recent findings.¹

These conclusions were the results of a new cross-sectional study—led by Brenda M. Chiang, MS, of the department of dermatology at the University of California, San Francisco—in which investigators sought to assess the extent to which dietary sodium intake increases were linked with eczema. Chiang and colleagues estimated this through the use of urine sodium as a biomarker.

The investigators noted recent findings indicating the majority of the human body’s exchangeable sodium is held within one’s skin, adding that skin sodium is known to be linked with inflammatory conditions.²

“A German textbook recommended a low-salt diet for AD more than a century ago, but data on the association between sodium consumption and AD are still lacking,” Chiang and colleagues wrote. “Our objective was to investigate whether there is an association between higher levels of sodium consumption and AD prevalence, activity, and severity at the population level.”³

Background and Methods

The investigators implemented a cross-sectional trial design and looked at data that had been drawn from the UK Biobank, including more than 500,000 participants in the age range of 37 - 73 at the time of recruitment from the National Health Service (NHS) in the UK. The Biobank participants are predominantly female, generally older, and often inhabit regions with lower socioeconomic deprivation.

The research team gathered their data through a single assessment visit between March 2006 - October 2010, supplementing the information with retrospective primary care records dating as far back as 1938. The team’s main focus was on 24-hour urinary sodium excretion, known to approximate around 90% of subjects’ dietary sodium intake per-day.

They evaluated this through biomarkers in the urine collected at a single time point, under the assumption they represented typical intake of dietary sodium. The INTERSALT equation, taking into account factors such as BMI, sex, age, and urine concentrations of sodium, potassium, and creatinine, was also implemented to estimate 24-hour urinary excretion of sodium.

The primary outcome assessed by the investigators was participants’ atopic dermatitis, identified through a validated algorithm. The date of a subject’s diagnosis was identified to be the later of the 2 dates of prescription, ranging from 1987 - 2017.

Subjects deemed likely to have active eczema symptoms around the urine collection timeframe were found by meeting several criteria and having the relevant clinical or prescription codes. They were also categorized by their disease severity based on their prescriptions, and a sensitivity analysis using ICD-10 codes for AD was also carried out by the team.

The investigators considered potential confounding variables to be risk factors for atopic dermatitis in terms of links between estimated 24-hour urinary sodium excretion and subjects’ disease.

Findings

The research team ended up with 215,832 subjects with an average age of 56.52 years, 54.3% of them having been reported as female. The team found that 3.01 grams per day was the average estimated 24-hour urine sodium excretion, and 5.0% were shown to have a diagnosis of atopic dermatitis.

Through the use of a multivariable logistic regression, the investigators’ analysis suggested that for each additional gram of estimated 24-hour urine sodium excretion, participants’ odds of having the skin disease were found to have increased (adjusted odds ratio [AOR] 1.11, 95% confidence interval [CI] 1.07-1.14).

Additionally, the research team found that the odds of active eczema rose (AOR 1.16, 95% CI 1.05-1.28), as did participants’ likelihood of greater disease severity (AOR 1.11, 95% CI 1.07-1.15). Through a separate validation cohort of 13,014 individuals from the National Health and Nutrition Examination Survey, a link was identified by the team between an increase of 1 gram in estimated dietary sodium intake and risk of current atopic dermatitis (AOR 1.22, 95% CI 1.01-1.47).

“Dietary sodium intake represents an interesting avenue for future research in understanding its unpredictable heterogeneity in disease course,” they wrote. “Our study opens the potential for future studies on restriction of dietary sodium intake as an intervention for AD that would be cost-effective, low risk, and widely available.”

References

1. ^{Chiang BM, Ye M, Chattopadhyay A, Halezeroglu Y, Van Blarigan EL, Abuabara K. Sodium Intake and Atopic Dermatitis. JAMA Dermatol. Published online June 05, 2024. doi:10.1001/jamadermatol.2024.1544.}
2. ^{Chattopadhyay A, Tully J, Shan J, et al. Sodium in the skin: a summary of the physiology and a scoping review of disease associations. Clin Exp Dermatol. 2023;48(7):733-743. doi:10.1093/ced/llad080.}
3. ^{Finkelstein H. Lehrbuch Der Sauglingskrankheiten. Julius Springer Verlag; 1921. doi:10.1007/978-3-662-25423-3.}