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

Abstract

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 (α index), in a large population of healthy subjects. We also compared the α indexes determined by power spectral analysis with cardiac baroreflex sensitivity measured by the phenylephrine method (BSphen). 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 α indexes: an α low-frequency (LF) index of cardiac baroreflex sensitivity that ranges around 0.1 Hz; an α high-frequency (HF) index reflecting cardiac baroreflex sensitivity corresponding to the respiratory rate; and α total frequency (α 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 α indexes were higher in the youngest age group (⩽ 34 years old) than in the three oldest groups. Notably, α 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]. BSphen 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 α indexes were correlated inversely with age. The index yielding the closest correlation with BSphen was α 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.