[Circadian profiles of blood pressure with respect to age]

The effects of ageing on nocturnal blood pressure (BP) and the circadian rhythm of BP were studied. Ambulatory BP and heart rate (HR) were monitored at 30-minute intervals for 24 hours, in 326 normotensive volunteers aged 15-83. The following groups were monitored: young: < 40 yrs, n = 177; middle: 40 yrs < or = - < 60 years, n = 100; old: 60 yrs < or =, n = 49 Firstly, the ratio of nocturnal fall (RONF) of BP (or HR) was calculated as follows: [(average day time BP (or HR)-average night time BR (or HR)]/averaged whole day BP (or HR) x 100. Then we calculated 2 measurements: 1. The dipper (RONF of BP (or HR) > or = 10% 2. The non-dipper. (RONF of BP (or HR) < 10%. A cosine fitting technique using the least-squares method was employed to find the circadian rhythm of BP and HR. The results of the study showed that the incidence of the non-dipper on systolic BP (SBP) was higher for old subjects than for young subjects. In addition, the nocturnal BP and HR were higher for old subjects than for young subjects. The circadian amplitude of HR was lower in old subjects. The circadian midline estimating statistic of rhythm (MESOR) or SBP increased with age. The circadian acrophase of BP and HR increased with age.

non-dippers of BP and HR were observed in any age groups. The frequency of BP and HR non-dipper was greater for old subjects than young subjects. This result may suggest the clinical significance of nocturnal BP and HR for the evaluation of hypertensive subjects.