There is growing interest in examining objective markers for early identification and behavioral intervention to prevent dementia and mild cognitive impairment in clinical and community settings.

To investigate the association between salivary alpha-amylase as an objective measure of psychological stress response and mild cognitive impairment for the implication of psychological stress in the development of mild cognitive impairment.

This cross-sectional study involved 865 participants aged ≥ 65 years. A saliva sample was collected in the morning, and the levels of salivary alpha-amylase were assayed. Mild cognitive impairment was evaluated using the Japanese version of the Montreal Cognitive Assessment; a score < 26 was indicative of mild cognitive impairment. A multivariable logistic regression model was used to examine the association of salivary alpha-amylase and mild cognitive impairment after adjusting for age, sex, current drinking status, current smoking status, body mass index, hypertension, diabetes mellitus, physical activity, education, social support, social network, and heart rate variability.

Salivary alpha-amylase was associated with mild cognitive impairment (the multivariable-adjusted odds ratio [95% confidence interval] for the 1-standard deviation increment of log-transformed salivary alpha-amylase was 1.24 [1.07–1.44]). This significant association persisted after adjusting for various confounding factors.

Elevation of salivary alpha-amylase was associated with mild cognitive impairment among Japanese community-dwelling older adults. This suggests that salivary alpha-amylase is a useful objective marker of psychological stress responses associated with mild cognitive impairment.