Symbolic dynamics of sleep heart rate variability is associated with cognitive decline in older men.

We aimed to investigate the association between autonomic and cognitive functions in older men. We investigated heart rate variability (HRV) during sleep using time domain metrics and symbolic dynamics analysis of inter-beat intervals. These metrics were statistically analysed for associations with cognitive function which was elicited by administering the modified mini-mental state examination (3MS) and the Trail making test part-B in older men participating in the MrOS sleep study.Multivariable linear regression adjusted for age, body-mass-index (BMI), apnea-hypopnea index (AHI) and arousal index (A.I.) showed that symbolic dynamics of HRV especially the 0V% which is a measure of sympathetic outflow to the heart during rapid eye movement (REM) sleep is significantly associated with 3MS and Trail B scores. In conclusion, nonlinear HRV during sleep provides a unique window to probe the association between cognitive and autonomic function.Clinical Relevance- This study shows that cognitive decline is associated with altered cardiac autonomic function.