Reducing Disability in Older Age

In this issue of THE JOURNAL, Freedman and colleagues¹ present encouraging evidence from a number of sources that disability in seniors is decreasing. The authors identified and reviewed 16 articles based on 8 surveys that assessed US trends in the prevalence of self-rated older adult disability and physical, cognitive, and sensory limitations among older adults beginning in 1982 through 1999. Of the studies assessed as having at least fair quality, surveys showed consistent declines in instrumental activities of daily living (IADLs) and in functional limitations. These findings are conservatively presented and all are consistent with the single best study, the report by Manton and Gu,² which presents the most recent data, has the most detailed end points, surveys the most representative sample of the US population, and shows the most striking findings. Manton and Gu studied trends in disability in the National Long Term Care Surveys (NLTCS) of 1982, 1989, 1994, and 1999 of the Medicare-eligible population aged 65 years and older, which include both institutionalized and noninstitutionalized individuals.

Surveying a sample that includes both institutionalized and noninstitutionalized older adults is important because the proportion of elderly individuals institutionalized declined from 6.8% in 1982 to 4.2% in 1999.² This increase in the number of persons with relatively greater amounts of disability into the noninstitutionalized population would be expected to decrease observed improvements in noninstitutionalized populations and to underestimate the actual decline, as may have occurred in some of the studies reviewed.¹ In the NLTCS, similar declines were observed in those with any disability, IADL disability, and activities of daily living (ADL) disability, with the greater declines seen in IADL. In general, declines in disability are greatest in the studies with the most recent data, and rates of decline appear to have accelerated after 1994, being 1.7% annually over the 17 years of the NLTCS and 2.6% per year from 1994 to 1999. A rapid decline in disability in blacks of nearly 4% per year, not seen previously, occurred from 1994 to 1999. It has been argued that a decline in any disability of 1.5% per year would ensure the long-term solvency of the Medicare and Social Security programs.³ These are important changes.

In 1980, I introduced the compression of morbidity hypothesis, suggesting that if the age of onset of disability could be postponed to a greater degree than senior life expectancy would increase, then lifetime disability could be compressed into a shorter average period and cumulative average lifetime disability could be reduced.⁴ Furthermore, if decreases in health risk factors such as lack of exercise, obesity, and cigarette smoking could be achieved in seniors, substantial postponement of disability might result and that, in general, preventive approaches to health enhancement and chronic disease prevention held the greatest promise for improving the health of older individuals. At that time, any suggestion that senior health futures could be improved was considered naively optimistic.^{5 - 6} Direct proof that morbidity could be compressed would be documentation that age-specific disability rates were declining more rapidly than age-specific mortality rates. The present data indicate that senior mortality rates are declining at about 1% per year⁷ and disability is declining at about 2% per year.² Thus, compression of morbidity is occurring nationally, and that certainly is good news.

Reasons for these trends are less clear. Improvements in lifestyle risk factors do not seem adequate to account for much of the change. Over the past 2 decades, the prevalence of obesity has increased,⁸ and exercise levels have not changed appreciably.⁹ The decline in cigarette smoking has been estimated to account for as much as 1 percentage point of the decline but cannot account for the complete decline.¹⁰ Arguments for major contributions from prostate-specific antigen testing, bone density screening, immunization rates, or other preventive services are not convincing.¹⁰ Health promotion and self-management programs have not been broadly adopted, and Medicare has remained reluctant to remunerate for preventive services.

The impact of improvements in medical care on reducing disability is difficult to quantitate. The number of total joint replacements and cataract surgery procedures have doubled over this period, and hypertension, diabetes, and hyperlipidemia are now treated more aggressively in elderly patients. However, access to care has not improved and access to prescription drugs may have decreased even as more effective drugs have become available.¹¹

Although medical care itself may be insufficient to explain the decline, the increasing expectations of aging adults to maintain good health may be self-fulfilling. Better health is associated with increased educational levels, and educational levels of older adults have been increasing.¹ Perceived self-efficacy, the belief that an individual can alter his or her own health future, is powerfully associated with health and offers a possible mechanism for the education and health associations.¹² Data for broad changes in senior self-efficacy, however, are lacking.

On balance, the reduction in disability is largely unexplained, and the most reasonable explanations are multifactorial.⁹ However, the present lack of clarity represents opportunity as much as it reveals ignorance. Multidisciplinary research with a finer grain is required to approach these questions. Regardless of the causes, however, several means to improve senior health have not yet been exploited and provide some promise that the current improvements may be continued and possibly accelerated. Two research areas not discussed by Freedman et al¹ suggest that the greatest future declines in disability may result from reductions in lifestyle risk factors.

Longitudinal studies of aging have shown strong associations between lifestyle risk factors and the incidence of disability, with substantial postponement of the onset of disability. A study of University of Pennsylvania alumni, initiated in 1986 at an average participant age of 68 years, documented postponement of disability by 7.75 years in those who exercised, had normal body mass indexes, and did not smoke compared with those who did not exercise, were obese, and smoked.¹³ The cumulative lifetime disability of those with low risks was one fourth that of those with high risks. In a study of vigorous exercisers and community controls, the heavy exercising group was projected to postpone disability for 12.8 years compared with controls.¹⁴ These disability postponements exceed any increases in life expectancy. In a study of the 418 members of the University of Pennsylvania cohort who had died,¹⁵ those without risk factors had slow progression of disability beginning 10 years before death, whereas those at high risk had more disability throughout and also experienced a surge in disability to high levels in the 2 years before death.

In addition, randomized trials of health promotion programs for seniors, especially those using tailored print interventions specific to the participant, demonstrate significant improvement in health risk reduction, health status, and reduced medical care utilization.^{16 - 17} Such programs hold promise for systematic approaches to improve senior health and potential attendant societal gains.^{18 - 19} The promise of healthier lives through active approaches to primary and secondary prevention may yet accrue.

In general, postponing premature morbidity is likely to be easier than postponing premature death, not only for medical and social approaches but also for prevention-oriented approaches. The most prevalent conditions of later life, such as osteoarthritis, depression, isolation, and Alzheimer disease, have relatively little effect on mortality yet cause immense amounts of morbidity; postponement of the onset of these disorders or improvement in their treatment should help decrease morbidity substantially without major effect on average life expectancy.

The health of seniors is one of the greatest medical problems facing developed nations and is one of the largest single economic burdens. An urgency of addressing these issues is increasingly recognized.^{19 - 20} In 2001, after an evidence-based review of senior health promotion programs determined that a Medicare demonstration project should be initiated, an experimental design project has begun with the goal of establishing effective health promotion as a Medicare benefit.²¹ A consortium of concerned institutions and individuals (http://www.HealthPromotionAdvocates.org) has formed to actively seek legislative action for federal support to develop the basic and applied science of health promotion. Subsequent legislation would seek support for programs for the most vulnerable segments of the population. A Sense of the Congress Resolution on Building Health Promotion into the National Agenda has attracted strong support in both the Senate and the House, and Healthy Senior bills have been presented in both houses of Congress.

In 1990 I wrote in THE JOURNAL an editorial titled "The Sunny Side of Aging"²² in which I urged a research agenda that would (1) establish an epidemiology of aging and trends in aging, (2) understand the fundamental basis of age-associated conditions and of nonfatal chronic illness, and (3) set a priority for documenting and implementing effective programs in prevention that could improve health and perhaps mitigate the economic consequences of unnecessary morbidity among older adults. It is still a good agenda, and a hopeful one, and health care has come quite a ways further along with it than it was. There are going to be a great many more older adults over the next decades, and it will be best if we are healthy seniors.