Association between Dietary Sodium Intake and Cognitive Function in Older Adults.

OBJECTIVE: To examine the association of dietary sodium intake with cognitive function in community-dwelling older adults.

DESIGN: Cross-sectional study.

SETTING: Southern California community.

PARTICIPANTS: White men (n=373) and women (n=552), aged 50-96 years from the Rancho Bernardo Study, a longitudinal study of cardiovascular disease risk factors and healthy aging.

MEASUREMENTS: During the 1992-1996 research clinic visit, a food frequency questionnaire was used to determine daily sodium intake; cognitive function was assessed with Trails Making Test, part B (Trails B), Mini-Mental State Exam (MMSE), and Verbal Fluency Test (VFT); and medical, clinical and demographic information was obtained. Linear regression was used to assess the association between calorie-adjusted sodium intake and cognitive test scores with adjustment for demographic, behavioral and health measures. Logistic regression examined the odds of having cognitive impairment by sodium intake.

RESULTS: Lower sodium intake was associated with poorer performance on Trails B (p=0.008) and MMSE (p=0.003) after controlling for age, sex, and education. Associations did not differ by sex, but there was a significant interaction by age for the Trails B: older (≥80 years), but not younger, adults showed worse performance with lower sodium intake (p=0.03). Associations remained significant after additional adjustment for smoking, alcohol intake, exercise, body weight, cardiovascular risk factors, kidney function, diuretic medication use, and diet quality. Lower daily sodium intake was associated with increased odds of cognitive impairment on the MMSE (score < 26; OR per SD decrease = 1.12, 95% CI 1.08, 1.16). Concluson: Lower sodium intake was associated with worse cognitive function in older community-dwelling adults. For the maintenance of cognitive health, older adults may be advised to avoid very low sodium diets.