Chronobiologic assessment of human blood pressure variation in health and disease

Summary

Once long and dense measurement series are available, biologic rhythm characteristics are readily computed. To assess such characteristics, we present suitable methods for blood pressure data collection and analysis. Since intra- and inter-individual differences are greater for blood pressure than for many other physiologic variables, any rhythm should and can be assessed for the individual subject by an inferential statistical approach. Circadian rhythms are thus mapped in human blood pressure in health and disease, under ordinary conditions and in social isolation, and can be shifted in their timing by changes in work schedule. Under all of the foregoing conditions, these rhythms account for a large part of the variability in blood pressure measurements. Their assessment renders changes in blood pressure predictable to a substantial degree, whereas their neglect can lead to false positive and false negative diagnoses of “hypertension”. Changes in a measure of the extent of reproducible change, such as the circadian amplitude, can lead to amplitude-hypertension occurring before the 24-h mean becomes elevated: mesor-hypertension. When changes in biologic rhythm characteristics precede an elevation of the 24-h mean of systolic blood pressure, they are harbingers of cardiovascular disease. Once automatic and/or self-measurement covers at least 48 hours with proper density, rhythmometry yields stable characteristics. High school students and adults alike can handle inferential statistical tests whereby rhythm characteristics a) are determined in actual or presumed health and b) may be found to be altered, the alteration (indicating, e.g., amplitude and/or mesorhypertension) prompting intervention. Statistical tests also gauge the effect of intervention, motivate compliance and thus contribute toward the success of preventive or curative measures. A system of education and software for rhythm analysis, wedded to hardware for self- and automatic blood pressure measurement, is particularly suitable for screening, diagnosis and the optimization by timing of non-drug and drug treatments to enhance the desired effect and to reduce side effects. Rhythmometry of data from room-restricted automatic monitoring demonstrates the effect of a shift from a betablocker to a placebo within 24 hours and corroborates it within 48 hours.