Author + information
- Received December 16, 1993
- Revision received July 7, 1994
- Accepted July 13, 1994
- Published online December 1, 1994.
- Sheila M. Ryan, MD∗,†,2,
- Ary L. Goldberger, MD, FACC∗,
- Steven M. Pincus, PhD∗,
- Joseph Mietus, BS∗ and
- Lewis A. Lipsitz, MD∗,†,‡∗,1
- ↵∗Address for correspondence: Dr. Lewis A. Lipsitz, MD, Hebrew Rehabilitation Center for Aged Research and Training Institute, 1200 Centre Street, Boston, Massachusetts 02131.
Objectives. This study aimed to quantify the complex dynamics of beat-to-beat sinus rhythm heart rate fluctuations and to determine their differences as a function of gender and age.
Background. Recently, measures of heart rate variability and the nonlinear “complexity” of heart rate dynamics have been used as indicators of cardiovascular health. Because women have lower cardiovascular risk and greater longevity than men, we postulated that there are important gender-related differences in beat-to-beat heart rate dynamics.
Methods. We analyzed heart rate dynamics during 8-min segments of continuous electrocardiographic recording in healthy young (20 to 39 years old), middle-aged (40 to 64 years old) and elderly (65 to 90 years old) men (n = 40) and women (n = 27) while they performed spontaneous and metronomic (15 breaths/ min) breathing. Relatively high (0.15 to 0.40 Hz) and low (0.01 to 0.15 Hz) frequency components of heart rate variability were computed using spectral analysis. The overall “complexity” of each heart rate time series was quantified by its approximate entropy, a measure of regularity derived from nonlinear dynamics (“chaos” theory).
Results. Mean heart rate did not differ between the age groups or genders. High frequency heart rate power and the high/low frequency power ratio decreased with age in both men and women (p < 0.05). The high/low frequency power ratio during spontaneous and metronomic breathing was greater in women than men (p < 0.05). Heart rate approximate entropy decreased with age and was higher in women than men (p < 0.05).
Conclusions. High frequency heart rate spectral power (associated with parasympathetic activity) and the overall complexity of heart rate dynamics are higher in women than men. These complementary findings indicate the need to account for genderas well as age-related differences in heart rate dynamics. Whether these gender differences are related to lower cardiovascular disease risk and greater longevity in women requires further study.
↵2 Dr. Ryan is the recipient of a 1991 Brookdale National Fellowship Award, New York, New York.
↵1 Dr. Lipsitz is the recipient of the Irving and Edyth S. Usen and Family Chair in Geriatric Medicine at the Hebrew Rehabilitation Center for Age J Research and Training Institute. Boston.
☆ This work was supported in part by the Hebrew Rehabilitation Center for Aged Research and Training Institute, Boston, Massachusetts; a National Institute on Aging Teaching Nursing Home Award (AG04390) and Claude Pepper Geriatric Research and Training Center Grant (AG08812) from the U.S. Public Health Service, Bethesda, Maryland; and by awards from the National Institute on Drug Abuse (P01-DA06316) and National Heart Lung, and Blood Institute (R01-HL-42172), National Institutes of Health, Bethesda, Maryland; National Aeronautics and Space Administration (NAG9572), Bethesda. Maryland; and the G. Harold and Leila Y. Mathers Charitable Foundation, Mt. Kisco, New York; and by a grant from the Colin Medical Instruments Corporation, San Antonio, Texas.
- Received December 16, 1993.
- Revision received July 7, 1994.
- Accepted July 13, 1994.