Despite numerous investigations, the determinants of healthy longevity require further clarification. Findings that aging is associated with decreasing heart rate variability (HRV), a marker of decreasing autonomic function, suggest that the converse (i.e., the persistence of high HRV) indicates good autonomic function and healthy longevity. To assess this matter, our group conducted a cross-sectional study of 24-hour Holter monitor records from 344 healthy subjects, aged 10 to 99 years, without known disease, significant arrhythmia, or significant medication histories, using 4 time-domain measures of HRV.

Our data clearly show that healthy longevity is associated with increases in parasympathetically modulated HRV measures (the root mean square of the successive normal sinus RR interval difference [rMSSD] and the percentage of successive normal sinus RR intervals >50 ms [pNN50]), findings in accord with conclusions that longevity is related to the persistence of good autonomic function, particularly good parasympathetic function. Although we are familiar with Stein et al’s findings of nonrespiratory “erratic rhythms” in the elderly, what is not clear is why the reported increase in erratic rhythms in the elderly is attributed solely to old age or why this precludes the use of HRV as an index of autonomic function particularly, given that their study was conducted in a nonuniform population with a wide range of health status, disease states, and medication use, all of which can influence heart rate, heart rhythm, and autonomic function.

Of equal importance, our subject selection process was designed to exclude those with significant arrhythmia other than sinus arrhythmia. We examined the records of our oldest subjects (aged ≥80 years) in particular detail and found virtually all rhythm irregularities to be of the respiratory sinus arrhythmia variety. Thus, conclusions that the frequent occurrence of ectopic and erratic rhythms in the elderly preclude the use of HRV as an index of autonomic function does not apply to our study population. In addition, conclusions that longevity is associated with the persistence of high levels of parasympathetic function are supported by power spectral studies showing that ultracentenarians exhibit lesser low-frequency (sympathetic) power and greater high-frequency (parasympathetic) power than do even slightly younger subjects. Findings that centenarians exhibit low sympathetic function/parasympathetic function ratios also are supportive.

Finally, Stein et al’s view that the high levels of pNN50 and rMSSD in the elderly are age related does not detract from the view that they reflect an underlying persistence of good parasympathetic activity in this population and that this contributes to longevity. In this regard, it would be of great interest to repeat the study on erratic rhythms in a healthy population not receiving significant medications.