A new study by University of Colorado at Boulder researchers indicates regular, moderate walking by women using hormone replacement therapy restored the flexibility of their large arteries, most likely reducing the risk of heart disease.
With advancing age, large arteries like the aorta and carotid lose their elasticity by roughly 50 percent, making it harder for them to expand and relax with each heartbeat, said Research Associate Kerrie Moreau of CU-Boulder's kinesiology and applied physiology department.Ìý
"Increases in the stiffness of these arteries can contribute to high blood pressure and enlarging of the heart, both risk factors for heart disease," she said. Cardiovascular disease, including strokes, is the No. 1 killer in the United States of postmenopausal women.
The carotid arteries are the two primary arteries on each side of the neck that carry blood from the heart's aorta to the head, said Moreau. Impaired elasticity in the carotid arteries also can be a factor in postural hypotension, a condition that occurs when blood pressure drops precipitously as a person changes body position.
Presented at the Experimental Biology 2002 meeting in New Orleans in late April, the study showed how relatively easy it may be to modify elasticity problems in arteries. Moreau and colleagues from CU's Human Cardiovascular Research Laboratory studied 69 healthy pre-menopausal and older post-menopausal women.
The researchers examined how hormone replacement therapy, or HRT, and exercise modify the age-related changes in the elasticity of arteries. They compared post-menopausal women who were sedentary and either using or not using HRT with women who participated in endurance-training exercise such as running.
They found the elasticity in the arteries was lower in all the post-menopausal women groups in comparison to the pre-menopausal women, she said. But post-menopausal women who were sedentary and using HRT and post-menopausal women who participated in regular exercise had a higher level of arterial elasticity than post-menopausal women who were sedentary and not taking HRT.
"There was no difference in arterial elasticity between sedentary women using HRT and those who exercised," said Moreau.
Moreau and her colleagues then had 12 healthy but sedentary post-menopausal women - whose average age was about 60 -- who had been taking HRT for a number of years participate in a walking program. The researchers found that having the women walk at a moderate pace for 40 minutes to 45 minutes a day five times a week for twelve weeks improved the elasticity of the carotid artery of the women by 48 percent -- levels similar to those in younger, pre-menopausal women.
"The findings demonstrate that HRT use and exercise both blunt the age-related changes in arterial elasticity and that combining HRT and exercise can restore elasticity to pre-menopausal levels in a relatively short period," Moreau said.
"The change in arterial stiffness seen in this study may help explain the recognized favorable benefit to cardiovascular health of regular aerobic exercise," said Moreau. It is significant that the study participants achieved the benefit of arterial elasticity without changing other factors known to influence heart disease, including blood pressure, cholesterol and body composition.
This is important because it shows exercise can be an alternative lifestyle intervention for women who do not want to take HRT or cannot take it because of side effects, doctors' advice or fear of breast cancer.
Post-menopausal women in the Denver-Boulder area who would like to participate in a clinical research study aimed at examining the effects of HRT and exercise regimens to improve their cardiovascular health can call the lab at (303) 735-6410 or email HRTstudy@colorado.edu.
Benefits from participation include a physician- supervised exercise stress test and echocardiogram of the heart and arteries. Participants also will be tested for body composition, including bone density and body-fat content, and will have their blood cholesterol concentration measured and receive a nutritional assessment of their daily diet.