The mean heart rate and systolic and diastolic blood pressures were comparable and they showed no significant differences between the diabetic (n = 48) and the healthy (n = 75) groups, and also between the elderly diabetic (n = 24) and the healthy elderly (n = 30) groups, before and after meal intake. However, both elderly groups showed a drop in mean systolic blood pressure on standing, of more than 20 mmHg, which confirmed the conclusions of other studies.[12
] The reported drop of more than 20 mmHg in the mean systolic blood pressure on standing observed in the two elderly groups in our study did not correlate well with diabetes mellitus, which is a known risk factor of orthostatic hypotension,[5
] but it did correlate well with aging, as it is noted in [Tables ,, and ]. In our study, we were not able to demonstrate any significant postural hypotension in the diabetic patients, when comparing them with the healthy subjects . This may be attributed to a better control of diabetes in our patients, who were regularly attending the Outpatient Clinic. They were University employees, expected to be more oriented in their health problems, and for that reason diabetes was not complicated by autonomic neuropathy. However, that finding may not represent the postural changes of diabetes in the general population.
To show further, the effects of aging in our study, we compared the mean supine and standing heart rate and systolic and diastolic blood pressures between the young adults ≤ 40 years old (n = 69), and the elderly group ≥ 65 years old (n = 54), before and after a meal. The results showed a highly significant postural drop in the mean systolic blood pressure of the elderly subjects, compared to a very small and insignificant drop in that of the young adults, as shown in Tables and , (P
< 0.0004). The drop in systolic blood pressure in the elderly group confirmed the conclusions of several other studies.[10
] Up to about 30% of the elderly subjects were reported to experience a significant drop in systolic blood pressure on standing.[12
The mean postural drop in systolic blood pressure in the elderly group in our study ranged between 25 and 28 mmHg. , which was greater than those changes reported in the literature.[20
] That difference may be attributed to variations in standardization of procedures, and may also be due to the higher environmental temperature in our area, compared to those areas where previous studies in the literature were conducted. The increased activity of the sweat glands at higher environmental temperatures may contribute to greater postural changes in blood pressure.
The reported increase in heart rate on standing was less and insignificant in our elderly group compared to the young adults. The increase of heart rate on standing was related to changes in the plasma norepinephrine level,[22
] and that increase was not found in some patients with orthostatic hypotension.[23
] Our study also demonstrated a higher resting heart rate in the elderly group ≥ 65 years old, compared to the young adults ≤ 40 years old, both in the supine and standing positions, as shown in . It was reported that heart rate variability diminished with advancing age, by using Power Spectral Analysis.[24
] The decreased compliance of the baroreceptors, which were responsible for correction of rapid changes in BP, were impaired.[2
] That impairment was mainly explained by arteriosclerosis, leading to loss of elasticity in the arterial walls with aging, and the loss of baroreflex sensitivity could be explained by changes in the arterial distensibility.
Our investigation demonstrated a defect in the reaction of the cardiovascular system in response to physiological stimuli, such as, standing upright or taking a meal, in the elderly group compared to the young adults. That defect was shown by a significant drop in the mean systolic blood pressure on standing, and by the relatively high mean resting heart rate in the elderly group. These findings were consistent with several previous studies on changes in cardiovascular reflexes with aging.[1
] The significant drop in systolic blood pressure observed in our elderly subjects was generally asymptomatic, however, that did not exclude the symptoms that occurred in the same individual at different times of the day. It was reported that a decrease in blood pressure following an upright tilt was a useful predictor of falls in older people.[25
Autonomic cardiovascular dysfunctions, particularly orthostatic hypotension should be considered seriously in all elderly people, particularly those at risk, for example, those with supine hypertension or those using vasodilator drugs. Elderly people should be advised to exercise caution and slow the process of changing positions from lying to sitting to standing. They should also be advised to take small frequent meals to reduce postprandial hypotension. The floors and stairs of the house should not be slippery, and loose rugs should not be used in the house, and light should be sufficient to reduce the possibility of fall, and they should not use inappropriate footwear. Blood pressure should be measured routinely in the supine and standing positions for all elderly people, to check for possibility of postural hypotension. These preventive measures may reduce the risk of the clinical outcome of postural hypotension, like dizziness or falls and fractures, which may lead to prolonged rehabilitation, and increase morbidity and mortality in the elderly.[26