Reduced sympathetic response to head-up tilt in subjects with mild cognitive impairment or mild Alzheimer's dementia.

BACKGROUND: Hemodynamic control was compared in patients with mild cognitive impairment (MCI) or mild Alzheimer's dementia (AD) as well as in healthy elderly subjects. METHODS: Noninvasive, continuous hemodynamic recordings were obtained from 14 patients and 48 controls during supine rest (tilt of 30 and 70°). Cardiac output, end-diastolic volume, total peripheral resistance, heart rate variability (HRV), systolic blood pressure variability (SBPV), and baroreceptor sensitivity were calculated. RESULTS: At 70° tilt, the HRV indices differed significantly, with higher high-frequency (HF) variability as well as lower low-frequency (LF) variability and LF/HF ratios in the patients. The patients had significantly lower SBPV in the LF range at 30° tilt. CONCLUSIONS: The results indicate a poorer sympathetic response to orthostatic stress in MCI and mild AD. © 2015 S. Karger AG, Basel.

Fit elderly men can also stand: orthostatic tolerance and autonomic cardiovascular control in elderly endurance athletes.

BACKGROUND AND AIMS: Endurance training may reduce orthostatic tolerance. Elderly people are prone to orthostatic intolerance, but the impact of endurance training in old age has been insufficiently explored. METHODS: 54 healthy men; 30 endurance athletes and 24 controls, free from medication and chronic diseases, were subjected to head-up tilt tests: 30º for 10 min and 70º for 40 min. Non-invasive recordings of blood pressures, heart rate, stroke volume, end diastolic volume, total peripheral resistance, heart rate variability, blood pressure variability, and baroreflex sensitivity were obtained. We registered terminations of test due to frank syncope or unbearable presyncopal symptoms. RESULTS: Mean age 71 years (range 65-84); athletes had lower body mass index (23.4 versus 24.8, p < 0.05) and lower resting heart rate (50 versus 61, p < 0.01). Blood pressures and total peripheral resistance were equal. End diastolic volume index, baroreflex sensitivity, and heart rate variability were higher among athletes, both HF-RRI (high-frequency variability, reflecting parasympathetic activity) and LF-RRI (low-frequency variability, reflecting both sympathetic and parasympathetic activity). Syncope or presyncopal symptoms occurred in 11 persons, 4 athletes and 7 controls (p = 0.2). Cox Regression analysis showed that higher heart rate at rest was the only variable associated with syncope. DISCUSSION: Orthostatic tolerance was not reduced among elderly endurance athletes. Rather, there was a trend towards better orthostatic tolerance, which might be attributed to stronger parasympathetic cardiovascular control and larger blood volume. CONCLUSIONS: Better orthostatic tolerance might be an additional benefit of physical activity in older age.

Gender differences in orthostatic tolerance in the elderly.

BACKGROUND: Gender differences in orthostatic tolerance in the elderly are poorly studied and understood. METHODS: 48 healthy elderly over 65 years (24 women), free from medication and without chronic diseases, were subjected to head-up tilt (HUT) tests: 30° for 10 min and 70° for 40 min. Blood pressures, stroke volume, total peripheral resistance, blood pressure variability, heart rate variability and baroreceptor sensitivity were measured and test terminations due to vasovagal syncope or unbearable presyncopal symptoms were registered. RESULTS: Mean age was 72; women and men differed in body mass index; 22.2 versus 24.8, respectively (p < 0.01). Mean blood pressures were lower among women, with 88 and 98 mmHg, respectively (p < 0.01) (rest) and 86 and 96 mmHg (p < 0.01) (tilt 30°). Mean total peripheral resistance index was significantly higher among women during 70° tilt, 13.5 versus 10.8 (p < 0.01); no gender differences in heart rate were seen. Women had lower LF/HF ratio (an index of sympathovagal balance) at rest and during 30° tilt (both p < 0.05); other heart rate variability measures and baroreceptor sensitivity did not differ. Two women, 9 %, and 8 men, 33 %, terminated head-up tilt test due to vasovagal syncope or presyncopal symptoms. Gender difference was marginally significant (p = 0.05, log-rank test). Higher heart rate at rest (p < 0.01) was the only variable significantly associated with the risk of syncope. CONCLUSIONS: Our results indicate that elderly men have poorer orthostatic tolerance during protracted postural stress than women of the same age. The underlying reason might be differences in vascular rather than cardiac autonomic control.