Circadian and circannual characteristics of blood pressure self-measured for 25 years by a clinically-healthy man.

Abstract

A normotensive, clinically healthy, diurnally-active man, 20.5 years of age at start of study, used an aneroid sphygmomanometer to self-measure systolic (S) and diastolic (D) blood pressure (BP) in triplicate several times daily during waking-only for > 340 days/year for 25 years. The 39,321 mean values (from 117,963 readings) were analyzed by year after editing for time-zone changes and overt illness. A significant time-effect of day and year could be demonstrated by ANOVA at p < 0.001 during each year for both SBP and DBP. Notwithstanding the lack of data during sleep, a circadian rhythm was described by the least-squares fit of a 24h cosmic (Single Cosinor analysis) at p < 0.001 for each BP during each year. Acrophases for SBP and DBP remained remarkably stable, with the circadian acrophase of DBP consistently occurring at midday (13(44) h) and that of SBP consistently occurring in the early evening (19(32) h). A circannual rhythm could be demonstrated in 24 out of 25 years for both SBP and DBP, with acrophases generally occurring between late Fall and early Spring. No trend over the 25-year observation span was found in SBP (p = 0.61), but one of +0.16 mmHg/y was detectable in DBP (p = 0.02), much less than the average circadian (3 - 5 mmHg) and circannual amplitudes (0.9 - 1.3 mmHg). As a complement to automatic around-the-clock monitoring, long-term self-measurement of BP (and other physiologic variables) is feasible and can cost-effectively provide individualized reference values (ranges, MESOR, amplitude, acrophase) in conjunction with the assessment of 1) multiple rhythmic components, 2) age, and 3) trends, thereby providing a reasonable guide for prognosis and diagnosis.