Читать книгу Pathy's Principles and Practice of Geriatric Medicine - Группа авторов - Страница 200

There are many ways in which physical activity may influence the development and expression of disability in old age. These theoretical relationships are now borne out in many epidemiological investigations and provide the rationale for both the experimental studies and exercise recommendations found in many recent reviews of this topic. For example, 1097 participants from the Established Populations for Epidemiological Studies of the Elderly (EPESE) study who were not disabled at baseline were analysed for factors related to disability‐free survival until death in old age. Physically active adults were more likely to survive to age 80 or beyond and had approximately half the risk of dying with disability compared with their sedentary peers. The most obvious conclusion from a review of the literature in this area is that there is a great deal of overlap between the identifiable risk factors for disability and the consequences or correlates of habitual inactivity. At the most basic level, shared demographic characteristics between those at risk of disability and those more likely to exhibit sedentary behaviour include advanced age, female gender, non‐Caucasian ethnicity, and lower educational level and income. Psychosocial features common to both cohorts include social isolation, low self‐esteem, low self‐efficacy, depressive symptoms, and anxiety. Lifestyle choices more prevalent in disabled and/or inactive adults include smoking and excess alcohol consumption. Body composition changes associated with both functional decline and inactivity include sarcopenia, obesity, visceral obesity, and osteopenia. Exercise capacity is typically reduced in both conditions in all domains, including aerobic capacity, muscle strength, endurance and power, flexibility, and balance. Gait instability and slowness and impaired lower extremity function and mobility characterise both disabled and inactive populations. Since most studies have not assessed the full complement of factors known to be associated with disability, and many have made observations at a single point in time, it is not possible to say with certainty how all of these complex relationships fit together, which relationships are causal, and which risk factors are independent of each other.

In addition to the associations above, chronic diseases associated with inactivity, such as obesity, osteoarthritis, cardiovascular disease, stroke, osteoporosis, type 2 diabetes, hypertension, and depression, are all risk factors for disability. In some cases, data linking inactivity to disability‐related diseases are available from cross‐sectional or prospective cohort studies and also experimental trials (e.g., diabetes, cardiovascular disease) and in other cases from epidemiological data alone (colon and breast cancer¹⁷⁴). Disability is complex and not fully explained by deficits in physical capacity such as strength and balance, and other pathways may be operative, including sensory function, glycaemic control, psychological constructs, and other aspects of health status.

Recent prospective and experimental studies have strengthened the hypothesised causal relationship between sedentariness, functional limitations, and disability in older adults. Miller et al. reported results from 5151 participants in the Longitudinal Study of Aging¹⁷⁵ and showed that physical activity was associated with a slower progression of functional limitations and, thereby, slower progression to ADL / instrumental activity of daily living (IADL) disability. In one of the largest reported randomised controlled trial of exercise and disability in frail elders to date,¹⁷⁶ 704 residents of nine different nursing homes were randomised into resistive, balance, and aerobic exercise; nursing rehabilitation; or control conditions. After 17 months, residents in both types of intervention homes had significantly less decline in ADL functioning than those in control homes.

A review of studies targeting disability in disease‐specific populations such as depression, cardiovascular disease, stroke, chronic lung disease, and arthritis is beyond the scope of this review, but there is evidence that exercise is beneficial in all of these conditions as a primary or ancillary treatment. The largest body of data exists for older adults with osteoarthritis of the knee, which is one of the commonest conditions related to disability in older adults.¹⁷⁷ Weight‐bearing functional exercises, walking, and resistance training have been used in various combinations in these studies, and there is no clear indication of the superiority of one modality over another in the reduction of pain and disability from osteoarthritis. Notably, land‐based exercise is superior to stretching and aquatic exercise, despite the common perception that these less‐robust exercises are more efficacious or feasible in this cohort.¹⁷⁷ It is likely that the disability reductions in arthritis are due to the impact of exercise on a variety of factors, including muscle strength, gait and balance, body weight, pain, comorbid disease expression, self‐efficacy, and depressive symptoms, among others, as there is no simple link between improvements in function or pain and fitness adaptations.¹⁷⁷