Baroreflex function in sedentary and endurance-trained elderly people.

Objective: to determine the differences associated with age and endurance exercise training on the baroreflex function of healthy subjects. Design: cross-sectional study. Setting: university research department. Participants: 26 (10 female) sedentary, healthy, normotensive elderly subjects (mean age 67 years, range 62-81), eight (two female) elderly endurance-trained athletes (66 years, 62-69) and eight (two female) young (30 years, 25-34) subjects. Measurements: baroreflex sensitivity was quantified by the α-index, at high frequency (HF, 0.15-0.35 Hz) and mid frequency (MF, 0.05-0.15 Hz), derived from spectral and cross-spectral analysis of spontaneous fluctuations in heart rate and blood pressure. Results: resting heart rate was significantly lower in endurance-trained athletes than sedentary elderly people (58 ± 12 versus 68 ± 11 min-1, P < 0.05) but not different to that in healthy young subjects (63 ± 9 min-1). α(HF) in sedentary elderly subjects (8.1 ± 4.2 ms.mmHg-1) was lower than both endurance-trained elderly athletes (14.8 ± 4.8 ms.mmHg-1, P < 0.05) and healthy young subjects (28.3 ± 21.8 ms.mmHg-1, P < 0.05) and was not significantly different between endurance-trained elderly athletes and healthy young subjects (P = 0.10). α(MF) in healthy young subjects (15.4 ± 8.8 ms.mmHg-1) was greater than in sedentary elderly subjects (6.5 ± 3.2 ms.mmHg-1, P < 0.01) and endurance-trained elderly athletes (6.9 ± 2.0 ms.mmHg-1, P < 0.01), while there was no significant difference between the two elderly groups (P = 0.66). Conclusions: both components of the baroreflex measured by the α-index show a decrease with age. Elderly endurance-trained athletes have less reduction in the high, but not mid, frequency component of the α-index compared with sedentary elderly subjects. Some of the age-related changes in baroreflex sensitivity may be related to physical fitness and activity levels.