Effects of Age on Circadian Blood Pressure and Heart Rate Rhythms in Patients with Primary Hypertension

Abstract

To evaluate whether circadian rhythms in blood pressure and heart rate are influenced by age, we analyzed 24-h ambulatory blood pressure and heart rate recordings from 31 patients with primary hypertension. Data were collected during hospitalization, after a drug-free run-in period. Set times were administered for lights-on, meals, and lights-off. Daytime napping was prohibited. The patients were divided into sex-matched groups of young (group I: 25-45 years, n = 9), middle-aged (group II: 47-57 years, n = 11), and old (group III: 57-74 years, n = 11) subjects. Hourly data were analysed by fitting a two-component cosine function (24- and 12-h periods). Amplitudes of the circadian rhythms in systolic blood pressure and heart rate were significantly reduced with age. This finding could be partly attributed to the recording of higher nocturnal values in older patients. Elderly hypertensives also evidenced a significantly greater ultradian component (12-h period) in the systolic blood pressure rhythm than did young patients, with the secondary afternoon decline in blood pressure being more pronounced in groups II and III. The 24-h acrophase of heart rate was found to occur approximately 1.6 h earlier than that of systolic blood pressure in the young group (p < 0.01). This phase advance of heart rate compared with systolic blood pressure was reduced to 1 h in group II (p < 0.05) and was not evident in group III (p > 0.1). These results indicate that circadian blood pressure and heart rate profiles of primary hypertensives change with age. Since measures were obtained in a typical clinical setting, these findings have implications for the diagnosis and treatment of hypertension in the elderly. The marked afternoon decline in blood pressure for the elderly patients may also render conventional cosinor analysis inappropriate for accurate description of the circadian rhythms of geriatric hypertensives.

Chronophysiology of the cardiovascular system

“…Jones et al (2006) also observed a further fall and rise in systolic blood pressure reactivity in the afternoon. This finding agrees with other observations on elderly people, including those with hypertension, of a secondary rise in blood pressure in the afternoon, especially after a nap is taken (Atkinson et al 1994;Dunbar & Farr 1996;Kawamura et al 2003;Scorzoni et al 1997). Since some cardiac events also show a secondary peak in the late afternoon or evening, these blood pressure changes have led to the hypothesis that daytime sleep or a ''siesta'' is also a significant risk factor for myocardial infarction and strokes (Bursztyn et al 1999(Bursztyn et al , 2002Campos & Siles 2000;Qureshi et al 1997).…”

Reactivity of Ambulatory Blood Pressure to Physical Activity Varies With Time of Day

“…A secondary afternoon peak in absolute values of BP has been found previously for elderly subjects. 6,9 Our data suggest that this peak could be mediated by a greater reactivity to changes in activity at this time, such as those resulting from an afternoon nap. 12 Participants did not keep detailed records of exactly when lights were switched on or off or when an upright posture was adopted after waking.…”

“…For example, a secondary fall and rise in BP has been demonstrated in the afternoon in the elderly, including those who are hypertensive. 9,10 This pattern is also observed in people who take an afternoon "siesta." 11 Interestingly, the siesta has been identified as a separate risk factor for sudden cardiac events, 12 but it is not known whether it is the daytime sleep, the increase in activity after the nap, or both components that mediate unfavorable BP changes.…”

Why do circadian biorhythms age?

“…An increased tendency to low amplitude, loose internal synchronization and poor response to external environmental time queues are documented for many characteristics of both human subjects and animals (Richardson et al 1982, Brock 1991, Vansomeren et al 1993, Atkinson et al 1994, Garciapatterson et al 1996, Forsling 1998, Driver 2000, Weinert 2000, Van Someren et al 2002. A shortened period of circadian rhythms was observed sometimes in old laboratory animals and elderly humans (Witting et al 1994, Deuschle 1997, Weinert 2000.…”