Influence of aging on cardiac baroreflex sensitivity determined non-invasively by power spectral analysis.

Aging reduces cardiac baroreflex sensitivity. Our primary aim in the present study was to assess the effects of aging on cardiac baroreflex sensitivity, as determined by power spectral analysis (alpha index), in a large population of healthy subjects. We also compared the alpha indexes determined by power spectral analysis with cardiac baroreflex sensitivity measured by the phenylephrine method (BS(phen)). We studied 142 subjects (79 males/63 females; age range 9-94 years), who were subdivided into five groups according to percentiles of age (25, 50, 75 and 95). Power spectral analysis yields three alpha indexes: an alpha low-frequency (LF) index of cardiac baroreflex sensitivity that ranges around 0.1 Hz; an alpha high-frequency (HF) index reflecting cardiac baroreflex sensitivity corresponding to the respiratory rate; and alpha total frequency (alpha TF), a new index whose spectral window includes all power in the range 0.03-0.42 Hz. Spectra were recorded during controlled and uncontrolled respiration. Under both conditions, all three alpha indexes were higher in the youngest age group (< or =34 years old) than in the three oldest groups. Notably, alpha TF was significantly higher in younger subjects than in the three oldest groups [14+/-1 ms/mmHg compared with 9+/-1 (P<0.05), 8.1+/-1 (P<0.001) and 8.1+/-1 (P<0.05) ms/mmHg respectively]. BS(phen) showed a similar pattern [12+/-1 ms/mmHg compared with 8+/-0.5 (P<0.001), 6+/-0.5 (P<0.05) and 6+/-1 (P<0.05) ms/mmHg respectively]. No significant differences were found for cardiac baroreflex sensitivity among the three oldest groups. All alpha indexes were correlated inversely with age. The index yielding the closest correlation with BS(phen) was alpha TF (r=0.81, P<0.001). Cardiac baroreflex sensitivity in normotensive individuals declines with age. It falls predominantly in middle age (from approx. 48 years onwards) and remains substantially unchanged thereafter. The elderly subjects we selected for this study probably had greater resistance to cardiovascular disease that is manifested clinically, with preserved cardiac baroreceptor sensitivity.