Excessive Dietary Salt Intake Exacerbates Cognitive Impairment Progression and Increases Dementia Risk in Older Adults.

Objectives: To investigate excessive dietary salt intake as an independent risk factor of cognitive impairment and dementia in older adults.

Design: Prospective, population-based cohort study.

Settings And Participants: Two thousand forty-one community residents aged ≥60 years were recruited between April 2007 and August 2009 from the Shandong area of China.

Measurements: Participants were classified into low, mild, moderate, and high salt intake groups according to urinary sodium measurements for 7 consecutive days. Global cognitive function was assessed at baseline and biennially thereafter using the Mini Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), Dementia Rating Scale (DRS), and Informant Questionnaire on Cognitive Decline in the Elderly. Demographics and apolipoprotein E (APOE) genotype were also obtained for each participant. Participants were monitored for 11.4 ± 2.0 years.

Results: During follow-up, MMSE, MoCA, and DRS scores decreased progressively faster with increasing salt intake (P < 0.05 among all intake groups). In total, 319 participants (13.74 per 1000 person-years) developed cognitive impairment. Compared with the low salt intake group, cognitive impairment risk was increased by 75% in the mild group (P = 0.027), 180% in the moderate group (P < 0.001), and 330% in the high group (P < 0.001) after adjustment for age, education, mean, and variability in visit-to-visit systolic and diastolic blood pressure, and APOE genotype. The hazard ratio for cognitive impairment increased by 1.59 (95% CI 1.40-1.79) with each 1-SD increment in salt intake after confounder adjustment (P < 0.001).

Conclusions And Implications: Excessive dietary salt impairs cognitive function and increases cognitive impairment risk in older adults independently of known risk factors, including hypertension and APOE genotype.