Association Between Heart Rate Variability and Home Blood Pressure: The Toon Health Study

BACKGROUND Although blood pressure (BP) is regulated by the autonomic nervous system, it is not fully understood how autonomic activity affects BP at home in the general population. METHODS Subjects were enrolled from 2009 to 2012 and included 1,888 men and women aged 30-79 years. We measured casual BP in the morning during health checkups and asked participants to monitor BP at home twice in the morning and evening for 1 week. The mean of the two measurements of mean arterial pressure (MAP) was calculated. Five-minute recordings of the pulse wave from a fingertip sensor were used to determine the following indices of heart rate variability (HRV): standard deviation of normal-to-normal RR intervals (SDNN), root mean square of successive differences in RR intervals (RMSSD), high frequency (HF) power, low frequency (LF) power, and LF/HF. RESULTS Sex- and age-adjusted means of casual MAR and morning and evening MAP at home were significantly different among quartiles of SDNN, RMSSD, and HF. When further adjusted for smoking, alcohol drinking, medication for hypertension, diabetes, sleeping hours, snoring, and mental health status, the associations were somewhat attenuated. Inverse relationships were found between the means of morning home MAR and RMSSD (P= 0.02) and HF (P = 0.051) after adjustment for confounders. The association between MAP and RMSSD, or MAP and HF was evident in individuals <65 years old. CONCLUSION Low HF and RMSSD, which reflect impaired parasympathetic nervous system activity, were associated with increased home MAP in the morning rather than in the evening.