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

Aging reduces cardiac baroreflex sensitivity. Our primary aim in the presen t study was to assess the effects of aging on cardiac baroreflex sensitivit y, as determined by power spectral analysis (alpha index), in a large popul ation of healthy subjects. We also compared the alpha indexes determined by power spectral analysis with cardiac baroreflex sensitivity measured by th e phenylephrine method (BSphen). We studied 142 subjects (79 males/63 femal es; age range 9-94 years), who were subdivided into five groups according t o percentiles of age (25, 50, 75 and 95). Power spectral analysis yields th ree alpha indexes: an alpha low-frequency (LF) index of cardiac baroreflex sensitivity that ranges around 0.1 Hz; an alpha high-frequency (HF) index r eflecting cardiac baroreflex sensitivity corresponding to the respiratory r ate; and it total frequency (alpha TF), a new index whose spectral window i ncludes all power in the range 0.03-0.42 Hz. Spectra were recorded during c ontrolled and uncontrolled respiration. Under both conditions, all three a indexes were higher in the youngest age group (less than or equal to 34 yea rs old) than in the three oldest groups. Notably, alpha TF was significantl y higher in younger subjects than in the three oldest groups [14+/-1 ms/mmH g 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 BS (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 alph a indexes were correlated inversely with age. The index yielding the closes t correlation with BSphen was alpha TF (r = 0.81, P < 0.001). Cardiac baror eflex sensitivity in normotensive individuals declines with age. It falls p redominantly in middle age (from approx. 48 years onwards) and remains subs tantially unchanged thereafter. The elderly subjects we selected for this s tudy probably had greater resistance to cardiovascular disease that is mani fested clinically, with preserved cardiac baroreceptor sensitivity.