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The fast orthogonal search method was utilized for the time-series analysis of insulin periodicities based on the 'basic-rest-activity cycle' (BRAC) phenomenon. Time-series analysis of insulin periodicities indicated the lack of autonomy for different systems. The multivariate study also indicated the primary regulatory activities of the autonomic nervous system and the hypothalamus. Furthermore, the autonomic, cardiovascular and neuroendocrine systems exhibited strong coupling and shared periodicities with insulin.

The autonomic, cardiovascular and neuronendocrine systems exhibit periodicity within a 24-hour day in a phenomenon known as ultradian rhythm. Processes such as cardiac output, thoracic fluid index, and the secretion of hormones such as epinephrine, norepineprine and leutinizing hormone were monitored and data was subjected to time-series analysis. These processes occurred in periods of 115-145, 70-100 and 45-60 minutes and point to a single system regulating periodicity.

A calculation of loss rates is reported for human structural and functional variables from a substantially larger data set than has been previously studied. Data were collected for healthy, non-smoking human subjects of both sexes from a literature search of cross-sectional, longitudinal, and cross-sequential studies. The number of studies analyzed was 469, and the total number of subjects was 54,274. A linear model provided a fit of the data, for each variable, that was not significantly different from the best polynomial fit. Therefore, linear loss rates (as a percent decline per year from the reference value at age 30) were calculated for 445 variables from 13 organ systems, and additionally for 24 variables even more integrative, such as maximum oxygen consumption and exercise performance, that express effects of multiple contributing variables and systems. The frequency distribution of the 13 individual system linear loss rates (as percent loss per year) for a very healthy population has roughly a unimodal, fight-skewed shape, with mean 0.65, median 0.5, and variance 0.32. (The actual underlying distribution could be a truncated Gaussian, an exponential, Poisson, gamma or some other). The linear estimates of loss rates were clustered between 0% and 2% per year for variables from most organ systems, with exceptions being the endocrine, thermoregulatory, and gastrointestinal systems, for which wider ranges (up to ~3% per year) of loss rates were found. We suggest that this set of linear losses over time, observed in healthy individuals between ages (approximately) 30 to 70 years, exposes the underlying kinetics of human senescence, independent of effects of substantial disease.