Association of 24-Hour Urinary Sodium-to-Potassium Ratio with Deep White Matter Lesions in Community-Dwelling Older Adults

Background: The urinary sodium-to-potassium (Na/K) ratio is an integrated biomarker associated with cardiovascular risk. However, its association with deep white matter lesions (DWMLs), a manifestation of cerebral small vessel disease (CSVD), remains unclear. We investigated the associations of the urinary Na/K ratio and albuminuria with DWMLs. Methods: We conducted a cross-sectional study of 296 Japanese adults (mean age, 68.7 years). Brain magnetic resonance imaging was used to assess DWMLs using the Fazekas scale, and lesions were classified as absent (grade 0) or present (grades 1?3). The urinary Na/K ratio and albumin excretion were measured using 24-h urine collections. Multivariable logistic regression models examined the associations between urinary biomarkers and DWMLs. Results: DWMLs were present in 119 (40.2%) participants. A higher urinary Na/K ratio was independently associated with DWMLs (odds ratio per 1?standard deviation increase, 1.44; 95% confidence interval, 1.09?1.90; P=0.010). Participants in the highest quartile had greater odds of DWMLs than those in the lowest quartile (odds ratio, 2.48; 95% confidence interval, 1.16?5.29; P=0.019). Urinary potassium excretion was inversely associated with DWMLs, whereas urinary sodium excretion alone showed no significant association. Findings were consistent across sensitivity and subgroup analyses. Conclusions: A higher 24-h urinary Na/K ratio was independently associated with DWMLs in older adults. This association appeared to be driven primarily by lower urinary potassium excretion rather than higher sodium excretion alone. The urinary Na/K ratio may serve as a simple, noninvasive marker of CSVD.