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LETTER TO THE EDITOR |
Department of Geriatric Medicine The Canberra Hospital Australia
Centre for Education and Research on Ageing University of Sydney and Concord RG Hospital Sydney Australia
Address correspondence to Professor David Le Couteur, CERA, Centre for Education and Research on Ageing, University of Sydney, Concord RG Hospital, NSW 2139, Australia. www.cera.usyd.edu.au. E-mail: dlecouteur{at}med.usyd.edu.au
To the Editor:
We read with interest the paper of Vloet and colleagues (1) on within-day variation in postprandial blood pressure (BP) in elderly people. The authors found that postprandial hypotension (PPH) is most prevalent in the morning. A similar pattern in BP response to meal intake was previously observed with nonstandardized meals and permitted medications (2). However, other investigators reported no significant differences between the postprandial changes during breakfast, lunch, or dinner in elderly healthy study participants (3) and in hypertensive patients (4). In the aged population, PPH is a very common disorder and a potential risk factor for serious cardiovascular events, cerebrovascular damage, and falls, so that understanding of this phenomenon is of practical importance.
The significant postprandial variation of BP during the day reported by Vloet (1) cannot be explained by the effect of medications, differences in volume, composition or temperature of meals, or the rate of gastric emptying (factors well known to influence PPH), as their studies were performed under standardized drug-free (for 24 hours) conditions. Because BP was measured with an automized oscillometric device, interobserver and intraobserver variability is also unlikely to be the cause of within-day postmeal variations.
In elderly participants, prolonged recumbency at night may cause nocturnal polyuria, reduced intraventricular volumes, and central hypovolemia, and, as a result, decrease cardiac output because the arterial baroreflex sensitivity is decreased and vasomotor and cardiac responses (increase in heart rate, stroke volume, and peripheral resistance) are reduced (blunted). Therefore, an insufficient increase in cardiac output after a meal may be more pronounced in the morning—and this will aggravate PPH.
A very important factor contributing to the variations in PPH during the day could be baseline hypertension with the morning surge of systolic BP. We and others have documented significant correlations between preprandial systolic BP and the fall in systolic BP (5–7), and this is again confirmed by Vloet and colleagues (1). As BP follows a circadian rhythm with peak levels in the early hours of the morning, more significant PPH occurs in hypertensive patients after breakfast (2,7,8). Moreover, we and others have found that essential hypertension is a significant risk factor for PPH (5,7,9,10,11), and antihypertensive therapy reduces the risk (7,12). Notably, baroreceptor dysfunction, an important underlying mechanism, is associated with both aging and hypertension (13,14). Impaired sympathoadrenal activation after meal intake was also reported in hypertensive patients with PPH (15). However, the number of hypertensive patients among the 14 participants included in Vloet's study (1) is unknown, but the mean systolic BP was 149 ± 5 (SE), and 8 patients had "cardiovascular disorders."
The morning period has also been associated with prevalence of orthostatic hypotension (16), greater risk for cardiovascular events (17), and strokes (18). In one study, most falls causing hip fractures in elderly people occurred between 9 AM and midday (19), while, in another study, the peak was in the afternoon (20). There were no seasonal variations in either study. Taken together, these data reemphasize the need of BP control throughout the 24-hour period and especially to prevent the morning surge in BP.
The number of symptomatic patients with PPH in Vloet's study (1) was high: 9, 11, and 6 of 14 participants after breakfast, lunch, and dinner, respectively. This may be a result of selection. Although PPH may cause syncope, angina, collapse, dizziness, weakness, visual disturbances, or falls (5,6), the majority of patients with PPH (defined as a fall in systolic BP of 20 mmHg or more), are asymptomatic (3,21,22). In elderly hypertensive patients, PPH is associated with advanced although asymptomatic cerebrovascular damage (4). In order to prevent serious cardiovascular and cerebrovascular disorders and falls related to inadequate hemodynamic response to meals, it seems prudent to shift our attention to screening of asymptomatic older populations for marked PPH. We have recently demonstrated in a series of 179 older people [aged 83 ± (7.0 SD) years] in residential care, that PPH occurred in 38%. Less than 10% had any symptoms after a meal, and in some symptomatic persons, there was no significant decline in BP (7). Moreover, a fall in systolic BP 
20 mmHg was not associated with a risk of falling in the last year or of recurrent falls. However, risk of falling significantly increased if postprandial seated systolic BP was 115 mmHg or less. It is reasonable to assume that the absolute level of the postprandial BP (rather than a 20 mmHg fall in systolic BP) is the main cause of inadequate blood supply to the brain, heart, and other organs resulting in symptoms and falls. The relationship between symptoms and postprandial absolute levels of BP in Vloets (1) series would be of interest.
In conclusion, PPH, a common sign of compromised BP homeostasis in elderly people, may be more prevalent and more pronounced after breakfast especially in hypertensive patients and/or as a result of decreased cardiac output caused by reduction in intravascular volume. Although often asymptomatic, marked PPH (postmeal systolic BP < 115 mmHg) should be considered as a significant risk factor for serious cardiac and cerebral events and falls. There is a need to revise the conventional criteria for diagnosis of PPH in elderly people. Adequate treatment of hypertension may improve PPH. Clinicians treating older people should be aware of these issues and measure postprandial blood pressure in hypertensive subjects and those at risk of falls.
References
This article has been cited by other articles:
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  R. W. M. M. Jansen Postprandial Hypotension: Simple Treatment But Difficulties With the Diagnosis J. Gerontol. A Biol. Sci. Med. Sci., October 1, 2005; 60(10): 1268 - 1270. [Full Text] [PDF]
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