Researchers at Johns Hopkins have determined that in people age 55 to 75, a moderate program of physical exercise can significantly offset the potentially deadly mix of risk factors for heart disease and diabetes known as the metabolic syndrome. More specifically, the researchers found that exercise improved overall fitness, but the 23 percent fewer cases were more strongly linked to reductions in total and abdominal body fat and increases in muscle leanness, rather than improved fitness.
The researchers' findings raise the importance of physical exercise in treating both men and women with the metabolic syndrome, a clustering of three or more risk factors that make it more likely for a person to develop heart disease, diabetes and stroke - including high blood pressure, elevated blood glucose levels, excess abdominal fat and abnormal cholesterol levels.
The study, to be published in the American Journal of Preventive Medicine and available online Dec. 30, is believed to be the first to focus on the role of exercise training in treating metabolic syndrome in older persons, a group at high risk for heart disease and diabetes.
"Older people are very prone to have the metabolic syndrome," said lead study investigator and exercise physiologist Kerry Stewart, Ed.D., professor of medicine and director of clinical exercise physiology and heart health programs at The Johns Hopkins University School of Medicine and its Heart Institute. "While each component of metabolic syndrome increases disease risk by itself, when combined, they represent an even greater risk for developing heart disease, diabetes and stroke."
To assess the benefits of a fixed program of exercise training, the Hopkins team studied a group of 104 older people for a six-month period between July 1999 and Nov. 2003. All of the participants had no previous signs of cardiovascular disease beyond untreated, mild hypertension. One half of the study participants were randomly assigned to a control group that received a booklet that encouraged increased activity, such as walking, to promote good health. The other half participated in a supervised series of exercises for 60 minutes, three times per week. The combination of exercises was designed to work all major muscle groups, the heart and circulation. These included aerobics on a treadmill, bicycle or stepper, plus weightlifting.
The Hopkins team measured the changes in participants' risk factors, body fat, and muscle and fitness levels, and found substantial improvements in the group that was exercising for six months. Aerobic fitness, as measured by peak oxygen uptake on a treadmill, increased by 16 percent, and strength fitness increased by 17 percent. The average weight loss in this group was only four pounds because much of the loss of fat was offset by increased muscle mass. The fat in the abdominal region, by itself an important risk factor for heart and metabolic syndrome, was reduced by 20 percent among people in the exercising group. The group that was not exercising had either no or significantly less improvement than the exercising group.
At the beginning of the study, 43 percent of all participants had the metabolic syndrome. By the end of the study, participants in the exercising group had no new cases of metabolic syndrome, and the condition had resolved in nine of them, a reduction of 41 percent. In the control group, eight participants no longer had the syndrome, while four new cases appeared, resulting in an overall reduction of only 18 percent.
"Older people can benefit greatly from exercise, especially to reduce their risk for developing metabolic syndrome," said Stewart. "Our results show that this population can be motivated to follow through with a moderate exercise program, and for some risk factors, such as abdominal fat, exercise can be as effective as what is accomplished today with drugs.
"A novel finding of our study was that the changes in disease risk factors with exercise training were more closely related to reductions in body fat, particularly abdominal fat, and increases in muscle tissue, rather than improvements in fitness.
"The results also confirm the value of exercise for managing multiple risk factors. Because so many older persons have or are at risk for metabolic syndrome, this study provides a very strong reason for individuals to increase their physical activity levels. They will reduce their fatness, and increase their fitness and leanness, while reducing their risk for heart disease and diabetes."
Estimates of the prevalence of metabolic syndrome range from 25 percent to 40 percent of American adults age 40 and older.
Funding for the study was provided by the Heart, Lung and Blood Institute, a member of the National Institutes of Health (NIH), with additional assistance from the Johns Hopkins Bayview General Clinical Research Center, also funded by the NIH. Other Hopkins researchers who took part in this study were Anita Bacher, M.P.H.; Katherine Turner, M.S.; Jimmy Lin, M.D.; Paul Hees, Ph.D.; Edward Shapiro, M.D.; Matthew Tayback, Sc.D.; and Pamela Ouyang, M.D.
Materials provided by Johns Hopkins Medical Institutions. Note: Content may be edited for style and length.
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