Changes in heart rate and heart rate variability over time in middle-aged men and women in the general population (from the Whitehall II Cohort Study).

Previous cross-sectional studies have shown that heart rate (HR) and HR variability (HRV) are influenced by several behavioral, biologic, and psychosocial factors. There are very few longitudinal studies that enable analyses of changes in HRV over time at an individual level. This study aimed to describe changes in HR and HRV in a general population setting and to determine predictors of HR and HRV at follow-up. From 1997 to 2004, 1,999 participants (29% women) in the United Kingdom Whitehall II Cohort Study had 2 measurements of cardiac autonomic function (mean time between measurements 5.47 years, range 4.07 to 6.93). The mean +/- SD age at the first measurement was 55.6 +/- 6.0 years. At baseline, men showed higher low-frequency power than women, suggesting that they may have higher sympathetic activity. Conversely, women had higher high-frequency power, indicating higher parasympathetic tone. Over the 5-year follow-up period, men and women had decreases in HR. Men had reductions in HRV in time and frequency dimensions, whereas women showed increases in HRV. In conclusion, the probability of being in the adverse quartile of HRV function and HR at follow-up was related to baseline exercise, body mass index, cholesterol, and blood pressure.