Sodium Intake and Socioeconomic Status as Risk Factors for Development of Age-Related Cataracts: The Korea National Health and Nutrition Examination Survey

PURPOSE Cataract is a very prevalent ocular disorder, and environmental risk factors for age-related cataracts have been widely investigated. We aimed to evaluate an association of dietary sodium intake and socioeconomic factors with the development of age-related cataracts. METHODS A cross-sectional case-control study based on the 2008-2011 Korea National Health and Nutrition Examination Survey. Dietary sodium intake was estimated using urinary sodium to creatinine ratio (U[Na+]/Cr). RESULTS Among a total 12,693 participants, 2,687 (21.1%) had cataracts and 10,006 patients without cataracts served as controls. The prevalence of cataracts increased with age and quartiles of U[Na+]/Cr (p for trend < 0.001). Multivariate logistic regression analyses revealed that factors related to the development of cataracts were age ≥ 50 years (adjusted odds ratio [aOR] 15.34, 95% confidence interval [CI] 13.31‒17.69), low income (aOR 1.85, 95% CI 1.64-2.09), low educational attainment (aOR 1.76, 95% CI 1.57-1.96), and high sodium intake (U[Na+]/Cr > 16.4 mmol/mmol; aOR 1.29, 95% CI 1.16-1.44). In a subgroup analysis, a robust effect on cataracts across U[Na+]/Cr quartiles was observed in patients ≥ 50 years of age (aOR 1.11, 95% CI 1.04-1.18), though not in younger patients (aOR 1.06, 95% CI 0.96-1.17). CONCLUSIONS Our results suggest that high sodium intake and low socioeconomic status may affect the development of cataracts, and that a low-salt diet could be helpful for the prevention of cataracts in an older population. Furthermore, efforts to close gaps in health services due to socioeconomic factors may contribute to a reduction in the prevalence of cataracts.