To examine levels and variance structure of systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR), we measured those 3 variables every 7.5 min for 24 h (approximately 192 samples each subject) by ambulatory monitoring in 2 nominated groups of normal volunteers: younger (Y; 8 men, 5 women, 24-44 years) and older (O; 13 men, 12 women, 50-95 years). Y and O did not differ in either sleep or wake means for HR and DBP. Mean SBP in O was 17 mm Hg higher than in Y during wakefulness. Thirty-four subjects had significant low frequency variations (presumably the circadian rhythm) in SBP, DBP and HR, regardless of age. A periodic model fitting the time series required a 9 h feature (rhythm) for Y and O in DBP for best reduction of mean square error. In addition, O regularly showed 3 h features in both SBP and DBP, a 6 h feature in DBP and a 9 h feature in SBP, which were absent in Y. Our results suggest that low-power ultradian rhythms may appear in both SBP and DBP after age 50, and possibly serve as dynamic markers of normal cardiovascular aging.

Activity Cycles↗

PubMedDate not supplied

Dynamic assessment of cognitive and cardiovascular performance in the elderly.

Dynamic measures of cardiovascular and cognitive performance have been used as a preliminary step toward developing predictors of decline in functional performance in older persons. Both batteries use multiple measures to examine the cooperativity of various aspects of performance, and both examine the subject's response to naturally occurring stresses. In these two senses, the measures are dynamic. For the cardiovascular measure we conducted ambulatory monitoring of blood pressure and pulse at 7.5-min intervals over a 24-h period. These parameters were analyzed simultaneously to examine changes in one relative to the others, using spectroscopy. After appropriate filtering, several dominant ultradian rhythms were noted, with periods of 47 min, 180 min and 6 to 8 h, the latter rhythm being present only in subjects aged greater than or equal to 60. A battery of computer-administered cognitive tests was developed to assess reaction time, visual recognition memory and word recognition memory. This testing allows for both a time and performance level grading. The results of the computer battery correspond well with those for standard neuropsychological tests. In general, performance declined with age, and reaction time increased. The computerized tests are faster, more consistently administered, and do not rely on a skilled professional for administration or analysis. They also provide a wide variety of measures that can be used in isolating components of performance. Once the acceptability and tolerance of older subjects toward such testing was established, attention shifted to questions of measurement stability and discriminant validity. Since the project's primary purpose is to predict subtle measures of decline in function, the battery's ultimate test is in its ability to correctly identify those about to change functional status. However, many different measures of status change are possible, and the predictive accuracy will depend on the outcome chosen. Subsequent work will focus on the predictors to refine measures and compare data collected at one point in time with the predictive power of change scores that reflect the individual subject's "signature." By-products of this work include a wealth of longitudinal physiologic and neuropsychologic data on older persons and tools that may be useful to the practicing physician.

Aged↗

PubMedDate not supplied

Application of control systems theory to physiology. Adrenal glucocorticoid control system.

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Adrenal Glands↗