4C.03

Abstract

Objective: To test the cross-sectional and longitudinal association of heart rate variability measured from 10-second electrocardiogram recordings with cognitive function in older subjects at high risk of cardiovascular disease. Design and method: We studied 3,583 men and women, mean age 75.0 years, who were enrolled in PROSPER (PROspective Study of Pravastatin in the Elderly at Risk) study. From baseline 10-second electrocardiograms the standard deviation of normal-to-normal RR intervals was calculated as the index of heart rate variability. Four domains of cognitive function testing reaction time, processing speed and immediate and delayed memory were assessed at baseline and repeated during a mean follow-up of 3.2 years. Using analyses of covariance, we calculated the adjusted mean values of baseline and annual changes of cognitive scores in thirds of heart rate variability. Results: Participants with lower heart rate variability had worse cognitive function at baseline including reaction time, processing speed and immediate and delayed memory (all p-values < 0.05). In longitudinal analysis, participants with lower heart rate variability had a steeper cognitive decline in reaction time (mean annual change of: 1.49 seconds in the lowest tertile, 0.84 seconds in the middle tertile and 1.06 seconds in the highest tertile, p-value = 0.05) and processing speed (mean annual change of: -0.51 digits coded in the lowest tertile, -0.45 digits coded in the middle tertile and -0.35 digits coded in the highest tertile, p-value = 0.009). There was no significant difference in annual changes of immediate and delayed memory between heart rate variability groups. All these associations remained unchanged after adjustment for medications, cardiovascular risk factors and co-morbidities. Conclusions: The present study indicates that lower heart rate variability measured from 10-second electrocardiogram recording is associated with worse executive function at baseline as well as future decline in executive function independent of cardiovascular risk factors and co-morbidities.