HEART RATE VARIABILITY AND COGNITIVE FUNCTION IN MIDDLE-AGE ADULTS: THE CARDIA STUDY

Abstract

Lower heart rate variability (HRV), a marker of cardiac autonomic dysfunction, has been associated with major risk factors of cognitive impairment. Yet the direct association of HRV with cognitive function remains relatively unexplored, particularly early in the life course. We used data from the Coronary Artery Risk Development in Young Adults to examine whether measures of HRV are associated with cognitive function in middle-age. In 2005 (our study baseline), two measures of HRV, standard deviation of normal-to-normal intervals (SDNN) and the root mean square of successive differences (RMSSD), were calculated using 10-second 12-lead electrocardiogram. Lower SDNN (2.6ms to 17.4ms) and lower RMSSD (2.2ms to 17.8ms) were defined as the lowest quartiles. Five years later, in 2010, three cognitive tests were administered including a test of verbal memory (Rey Auditory-Verbal Learning Test, RAVLT, range 0–15), processing speed (Digit Symbol Substitution Test, DSST, range 0–133), and executive function (Stroop interference). 2,118 participants (57.7% female, 42.2% black) with a mean baseline age of 45.3 years were included in this analysis. In demographic-adjusted models, compared to participants with the upper three quarters of SDNN, participants with lower SDNN scored 1.76 points worse on DSST (p=0.01) and 1.14 points worse on Stroop (p=0.02). After adjusting for behavioral and cardiovascular risk factors, lower SDNN remained significantly associated with worse stroop (p=0.01) but not with DSST. There was no association between RMSSD and cognitive function. Our findings suggest that lower SDDN is associated with worse executive function among middle-aged adults, above and beyond cardiovascular risk factors.