Serum Sodium in Relation to Various Domains of Cognitive Function in the Elderly US Population
Abstract Background:Recent evidence suggests that sodium imbalances may be associated with cognitive impairment; however, the association between specific domains of cognition remains unclear. This study examines the association between serum sodium levels and immediate and delayed verbal memory as measured by the CERAD Word Learning Test (CERAD WLT), executive function as measured by the Animal Fluency test (AFT), and sustained attention, working memory, and processing speed as measured by the Digit Symbol Substitution test (DSST) in the elderly population of the US aged 60 and older who participated in the 2011–2014 National Health and Nutrition Examination Surveys (n=2,700). Methods:Cognitive function tests were performed by trained interviewers and sodium levels were measured using indirect ion selective electrode methodology. Results:After adjusting for all covariates, CERAD WLT scores showed significant positive associations with sodium levels (Immediate recall (IR) β = 0.11 (SE = 0.04, p-value 0.018); Delayed recall (DR) β = 0.07 (SE = 0.03, p-value 0.009)). Compared to individuals with normal sodium levels, individuals with hyponatremia were significantly associated with lower CERAD WLT-DR (β = -0.71, SE = 0.23, p-value 0.005) and AFT scores (β = -1.58, SE = 0.68, p-value 0.027), and showed a borderline significant relationship with lower CERAD WLT-DR scores (β = -1.11, SE = 0.56, p-value 0.057). Individuals with hypernatremia did not show any significant relationships with cognitive test scores, compared to those with normal sodium levels. Conclusions:Our cross-sectional study showed that lower sodium levels were associated with cognitive change, especially regarding memory and executive function.