Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 173

The effects of exercise on total mortality are unlikely ever to be substantiated via randomised controlled clinical trials, given the impossibility of random assignment to various physical activity regimens over many decades. However, there is clear evidence of an inverse, linear dose‐response relationship between the volume of physical activity reported in epidemiological studies (with sample sizes ranging from fewer than 500 to over 2.5 million individuals) and all‐cause mortality rates.¹ These relationships are demonstrable for both men and women and for both older and younger adults. Volumes of energy expenditure during exercise of at least 1000 kcal per week reduce mortality by about 30%, whereas reductions of 50% or more are seen with volumes closer to 2000 kcal per week, when more precise measures or estimates of physical activity participation incorporating fitness assessments are utilised instead of surveys. These changes in all‐cause and cardiovascular mortality translate to an increase in life expectancy of ~2 years for those exercising at such volumes. In a recent example, in a cohort study of 16,741 women with a mean age of 72, women who averaged approximately 4400 steps/day had significantly lower mortality rates during a follow‐up of 4.3 years compared with the least active women who took approximately 2700 steps/day. More steps taken per day were associated with lower mortality rates until approximately 7500 steps/day.³⁴

Despite the consistency of the data from well‐designed observational studies, many questions remain regarding the minimum threshold for efficacy; the effect of exercise intensity, duration, and frequency (apart from contributions to overall volume); the effect of non‐aerobic modalities of exercise; and the mechanisms of benefit. From a public health perspective, if small, effective doses of moderate‐intensity activity are found to be as beneficial as longer bouts of vigorous activity, adoption of mortality‐reducing physical activity recommendations by sedentary middle‐aged and older adults may be more successful. Of particular relevance to the exercise prescription for this cohort are studies that have demonstrated that a change from a sedentary to a more active lifestyle in midlife or beyond is associated with a reduction in mortality. In the sections that follow, the focus is on changes in functional capacity, physical fitness and body composition, quality of life, and disease burden, rather than on changes in longevity itself. It is in these domains that the centrality of physical activity patterns to optimal ageing is perhaps most relevant to the concerns of the healthcare professional and the older individual.