Salt added at the table, APOE genotype and incident dementia

Background: The frequency of salt added at the table (i.e., to food after it has been prepared, during consumption) could reflect an individual's long-term dietary preference and habitual intake in Western countries. However, little is known about the association between the frequency of salt added at the table and incident dementia. This study investigates the association of the frequency of salt added at the table with the risk of dementia and explores differences in the associations among people with apolipoprotein E ε4 genotypes.

Methods: Individuals indicated whether they added salt to their food at the table (salt used for cooking was not included) "never/rarely", "sometimes", "usually", or "always". Cox proportional hazards models were used to compute hazard ratios with 95 % confidence intervals and evaluate the association between the frequency of salt added at the table and incident dementia.

Results: We observed a graded relation between the frequency of salt added at the table and spot urine sodium concentrations and estimated 24-h sodium excretion. Over a median follow-up of 13.7 years, there were 9373 cases of all-cause dementia, including 4119 of Alzheimer's disease and 2052 of vascular dementia. With a higher frequency of salt added at the table, the risk of all-cause dementia, Alzheimer's disease and vascular dementia increased in a monotonic manner after adjustment for potential confounding factors (all P-trend <0.001). These associations of the frequency of salt added at the table with the risks of all-cause dementia, Alzheimer's disease and vascular dementia were greater in apolipoprotein E ε4 heterozygotes and homozygotes.

Conclusion: Our study showed that a higher frequency of salt added at the table was associated with a higher risk of incident dementia. This positive association was more prominent among individuals with apolipoprotein E ε4 heterozygotes and homozygotes.