Abstract 51: Heart Rate Variability and its Association with Cognitive Decline Over 20 years: The Atherosclerosis Risk in Communities - Neurocognitive Study

Background: Heart rate variability (HRV) reflects activity of the sympathetic and parasympathetic nervous systems. Low HRV is associated with an increased risk of heart disease and mortality, and risk factors for lower HRV are also linked to cognitive impairment. We assessed whether HRV measures are associated with cognitive decline in the Atherosclerosis Risk in Communities (ARIC) study. Methods: We studied 10,623 individuals (23% African-American, 57% female, mean age 54). HRV measures were obtained from 2-minute electrocardiogram rhythm strips in 1987-89 and include the standard deviation of all normal RR intervals (SDNN), root mean square of successive differences (rMSSD), low frequency (LF) and high frequency (HF) spectral power, and the LF/HF ratio. Cognitive function was measured in 1990-92, 1996-98 and 2011-2013 using 3 neuropsychological tests: Delayed Word Recall (DWR), Digit Symbol Substitution (DSS), and Word Fluency (WF). Scores were standardized and their average was used as a test of global cognitive function. HRV measures were log-transformed and we used linear regression models fit with generalized estimating equations to evaluate associations with cognitive performance over time, which was modeled as a linear spline with a knot at year 6 of follow-up. Results: At baseline, lower levels of HRV were significantly associated with reduced scores in all cognitive tests. Lower baseline levels of HRV measures of sympathetic activity (LF and LF/HF ratio) were associated with faster decline in tests evaluating executive function and language (DSST and WF) (table). We did not observe associations between parasympathetic nervous system measures (rMSSD and HF) and cognitive decline. Conclusion: In this large population-based study, markers of cardiac sympathetic dysfunction measured in mid-life were associated with a faster decline in executive function, which is more frequently affected in cognitive impairment of vascular origin. Additional research should explore the mechanism for this association.