Broadband spectral analysis of blood pressure and heart rate variability in very elderly subjects

Systolic blood pressure (SBP) variability is increased and R-R interval variability is reduced in the elderly. Little is known, however, about how SBP and R-R interval variabilities change in the very elderly. More important, however, it is not known which frequency components of SBP and R- R interval variability are affected significantly. We addressed this issue in subjects older than 70 years by broadband spectral analysis, which allows all variability components from the lowest to the highest frequency to be considered. In 20 very elderly normotensive subjects (mean±SD age, 78.1±6.8 years) and 28 normotensive adult subjects (36.1±7.1 years), noninvasive finger blood pressure and R-R intervals were recorded continuously for 30 minutes in the supine position and 15 minutes in the upright position. SBP and R-R interval power spectral densities were computed over the entire frequency region between 0.005 Hz (0.007 Hz in the upright position) and 0.5 Hz. Overall SBP variability (SD) was greater and overall R-R interval variability was less in very old subjects than in adult subjects. All spectral R-R interval powers were reduced significantly in very elderly individuals. The spectral SBP powers were greater in the very elderly group than in the adult group only in the very-low-frequency range (