Salivary Alpha-Amylase Activity in Relation to Cardiometabolic Status in Japanese Adults without History of Cardiovascular Disease

Aims: Stress is known to be a potential contributor to the development of diabetes and hypertension. However, the biological mechanisms underlying the association between cardiometabolic risk markers and the biological stress response have not yet been determined. Therefore, we examined salivary alpha-amylase and heart rate variability in relation to cardiometabolic status in a sample of healthy Japanese men and women. Methods: Participants (473 men and 1,029 women aged 30-84) underwent a 75 g oral glucose tolerance test after a 10-hr fast. The homeostasis model assessment index for insulin resistance was based on fasting and 2-hr postload glucose and insulin concentrations. Sitting blood pressure was measured twice after rest. A saliva sample was collected in the morning and salivary alpha-amylase was assayed. A 5-min heart rate variability recording was evaluated using time-domain indices of standard deviations of normal-to-normal intervals and root mean square of successive differences. Multivariate linear regression models were used to estimate associations between salivary alpha-amylase and each outcome measure. Results: Salivary alpha-amylase was associated with fasting glucose (β=0.008; 95% CI=0.002, 0.014), 2-hr postload glucose (β=0.023; 95% CI=0.004, 0.041), homeostasis model assessment index for insulin resistance (β=0.032; 95%CI=0.000, 0.064), systolic (β=1.603; 95% CI=0.479, 2.726) and diastolic (β=0.906; 95% CI=0.212, 1.600) blood pressures among women. These associations remained significant after further adjustment for heart rate variability measures. Conclusions: The elevation of salivary alpha-amylase may reflect a dysfunction of the sympathetic nervous system associated with cardiometabolic abnormalities in women.