Reduced heart rate variability is associated with worse cognitive function in elderly Mexican-Americans

Abstract

Heart rate variability (HRV) is a subclinical measure of central autonomic function. Reduced HRV has been found to be a strong predictor of cardiovascular risk factors, cardiovascular events and mortality. Therefore, reduced HRV may be associated with cognitive neurodegeneration. Yet this has been relatively unexplored, particularly in minority populations. We investigated whether autonomic nervous system dysfunction, measured as reduced heart rate variability, was associated with worse cognitive function in elderly Mexican Americans. The Sacramento Area Latino Study on Aging (SALSA) is a prospective cohort study of 1,789 community-dwelling Mexican-Americans aged 60–101 years at baseline in 1998–1999. SALSA includes seven annual study visits. HRV was measured in a total of 869 subjects who participated in either visit 5 or 6 and thus constituted our analytical sample. HRV was assessed using the ANS2000 which is an ECG monitor and respiration pacer measuring variability in heart rate in response to deep breathing. Cognitive function was assessed using the Modified Mini Mental State Exam (3MS), a 100-point test of global cognitive function. For ease of interpretation, we categorized HRV into quartiles (Q1 to Q4: reduced to high HRV). We fit linear regression models to estimate the associations between quartile of HRV and cognitive function (3MS). Our sample of 869 participants had a mean age of 75 years (SD=6.1) and included 59% females. A total of 14% of the participants reported having had a stroke, 41% had type-2 diabetes, and more than 90% had hypertension. Reduced HRV was associated with older age, lower education, having had a stroke, a diagnosis of type-2 diabetes, hypertension, and elevated depressive symptoms. In models adjusted for age, gender, education, diabetes, stroke, and depressive symptoms, compared to subjects in the highest quartile of HRV, those in quartile 1 had a 4-point lower mean 3MS score (p<0.01), those in quartile 2 had a 2-point lower mean 3MS score (p=0.04), and those in quartile 3 had a 1-point lower mean 3MS score (p=0.35). Reduced HRV is associated with worse performance on the test of global cognitive function, above and beyond traditional cardiovascular risk factors.