The Relationship Between Brain–Heart Autonomic Signaling and Aging: A Gender-Specific Longitudinal Perspective from the Baltimore Longitudinal Study on Aging

Abstract

<h3>Background</h3> Low heart rate variability (HRV) has been previously associated with adverse cardiovascular outcomes in high-risk populations or subjects with previously documented cardiovascular conditions. Information about HRV in healthy subjects is, however, scant. Moreover, gender effects of HRV in healthy subjects have not being well described. The objective of this study was to evaluate aging-related changes of the autonomic nervous system as measured by HRV in a cohort of healthy subjects. <h3>Methods</h3> We evaluated 368 subjects from the Baltimore Longitudinal Study on Aging (BLSA) who had 2 or more Holter studies with time-domain variables lasting 24 hours. The study population is a series of healthy volunteers of different ages, starting at 20 years old, followed indefinitively with a series of evaluations over time. The data were analyzed using linear mixed effects that account for unbalanced unequally spaced observations using SAS® 9.2 software, which is characteristic of the BLSA cohort. The number of pairs of successive NNs that differ by >50 ms (pNN50), the standard deviation of NN intervals (SDNN), and the standard deviation of the average NN intervals (SDANN) were used to measure HRV. <h3>Results</h3> Average age of participants in this study is 65.3 years (range 20–97 years). We found a statistically significant difference on HRV variables and gender, with women having lower HRV values than men (pNN50 –5.416%, <i>P</i> = .002; SDNN –18.974 ms, <i>P</i> = .0001; SDANN –12.945 ms, <i>P</i> = .0001). When each variable was analyzed by gender, our study did not show a significant longitudinal association between aging and changes in HRV, but it did show a significant cross-sectional association. This association is characterized by lower HRV variables measurements in later ages of life compared to earlier ones. <h3>Conclusions</h3> Our study shows that changes in HRV are gender dependent, with women having lower HRV than men at any given age. We also found that HRV variable measurements are lower in advanced ages compared to younger ones.