Physical Activity and Older People: A Walk A Day Keeps the Doctor Away

Over the past two years the Journal has published more than a dozen articles about exercise in older people. Moreover, literally hundreds of articles have been published in the top medical and scientific journals throughout the past 10 years on the topics of exercise, aging, and health. Taken together, this body of literature supports the hypothesis that exercise, and, more broadly physical activity, is an important determinant of health and independence in old age. Several points regarding the relationship of exercise and aging have been established. First, there is strong experimental evidence to show that healthy older people can exercise safely and that regular exercise will improve measures of physical fitness such as aerobic power, strength, balance, and flexibility.1–4 Furthermore, there is accumulating evidence that frail, chronically ill older people are able to exercise and improve their physical fitness.5 Second, both experimental and observational studies affirm that older people who participate in an exercise program have improvements in risk factors (lipids, insulin resistance, bone density, etc.) for many of the major chronic diseases.6–9 Third, epidemiological evidence suggest that high levels of physical activity are associated with lower rates of incident adverse health outcomes such as physical disability, falls, hip fractures, and mortality.10–14 Additionally, a recently published experimental study has shown that older persons assigned to one of several exercise programs had fewer falls than those in a control group.15 Given the consistent evidence that exercise is good for older people, are there new areas of research to be pursued? The study by LaCroix et al. in this issue of the Journal is indeed a step forward.16 In their study, 1645 community-dwelling older adults, who were members of an HMO and did not have cardiovascular disease, were followed for a period of 4.2 years to determine if the total time spent walking in all activities was associated with a reduced rate of hospitalization for cardiovascular disease. The results showed that people who walked more than 4 hours per week were 31% less likely to be hospitalized for cardiovascular disease than those who walked less than 1 hour per week. The association was present in both sexes, all age groups, and in people with physical limitations. One interpretation of these findings is that people who walked more, did so because they were healthier or that walking was a marker for participation in more vigorous exercise. However, the association of walking with decreased hospitalizations for cardiovascular disease persisted after adjusting for potentially confounding variables such as measures of health status, and the association was found in people who did not participate in vigorous physical activities. There are limitations to this study, most of which the authors readily acknowledge. The number of hospitalizations for each cardiovascular disease category was relatively small, and different diseases had to be combined to give a summary endpoint. Therefore, one cannot discern the association of walking with specific diseases, although the data suggest that much of the effect was attributable to fewer hospitalizations for coronary heart disease. Moreover, the association of walking with the overall rate for all hospitalizations is not given. However, there was an association of walking with total mortality, which strengthens the findings. The study cohort is not representative of the general population. Thus, the findings need to be replicated in other cohorts of older adults. Finally, this is a study of associations, not cause and effect. These limitations notwithstanding, the results of the study are potentially very important for the health of older people. The data suggest that moderate amounts of walking, the most common and basic of all physical activities, accumulated throughout the day, may be sufficient to provide major health benefits to older adults. These data are consistent with the recent recommendations from the Centers for Disease Control and Prevention and the American College of Sports Medicine to accumulate 30 minutes of moderate level physical activity per day.17 Thus, if older adults engage in daily activities that require a half hour of walking, traditional exercise may not be necessary to improve their health. It is likely that physical activity accumulated as part of an active lifestyle (engaging in a variety of moderate intensity activities that increase caloric expenditure) will be more accepted by older adults than traditional exercise programs (repetitive activities designed to improve physical fitness).9 Interventions that encourage adults to be more physically active throughout their day should be tested against traditional exercise programs to determine the effects on physiological variables and health outcomes.17 See also p 113 As gerontologists, we have a challenging task to convince older people to be more physically active. Despite the fitness boom of the last 20 years, most older Americans do not meet the recommended levels of physical activity.9,17 Furthermore, even if older people are willing to begin a physical activity program, keeping them active is difficult. A recent study by King et al. showed that up to half of healthy middle-aged and older adults who were enrolled in a walking program dropped out within 2 years, although the compliance rates varied some according to the intensity and location of the program.7 It is likely that the health benefits of physical activity wane rapidly when the physical activity is stopped. Thus, developing effective strategies to get older people to engage in and sustain physical activity should be a high research priority.19,20 We may have a new ally in our efforts to get older people to be more physically active. Health Maintenance Organizations (HMO) who enroll Medicare recipients have a strong financial incentive to keep their enrollees healthy and, specifically, to prevent hospitalizations. The latter is the largest expense for a Medicare HMO. In the LaCroix paper, those who walked more than 4 hours per week had a 31% lower rate of hospitalizations for cardiovascular disease than the non-walkers, a potentially large savings. Thus, developing and implementing strategies to increase the physical activity of older enrollees may be a good investment for HMOs. Most HMOs don't have the in-house expertise to design and evaluate the cost effectiveness of preventive services. Joint ventures between academia and the HMO make good sense in this regard. In summary, the evidence points to one conclusion: physical activity is good for the health of older people. Physicians and other health care providers should now encourage their older patients to be physically active. However, we need to know more about the effects of different types of physical activity on health outcomes as well as what are the most effective strategies to encourage and maintain physical activity in older people.