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 degrees for 10 min and 70 degrees 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 degrees). Mean total peripheral resistance index was significantly higher among women during 70 degrees 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 degrees 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.