Aging and Health - Health Research

Over the last 50 years, life expectancy has steadily increased for both men and women in the United States. For much of that period, those years of added life were years free from disability. In the most recent period, however, that trend toward improvement may be stalling or perhaps even reversing. Understanding the changing pattern of the trend in health in later life has implications for individuals, families, and public spending. Changes on a number of dimensions of health in the elderly population (i.e., persons aged 65þ) have been documented in recent US surveys. Similar to Manton (2001), this article reviews the magnitude and substance of the changes in mortality, disease prevalence, and functioning and disability, and consider such of those factors that are shaping the current patterns and their implications for health and healthcare.

Introduction: Dimensions of Health

The definition of what is meant by ‘health’ is an important part of any discussion of health status. For many decades, mortality was assumed to be an adequate measure of the health of the elderly. Rapid mortality declines since the 1960s, especially for women, however, raised the question of whether these years of added life were years of good health. Answering this question has involved a considerable effort by researchers for the past several decades. One of the important early discussions of this topic outlined the link between different dimensions of health – mortality, disease prevalence, and disability. Crimmins (1996, 2004) discussed the interrelationship of the dimensions of health status and pointed out that due to differences in the processes driving each, we should not expect all measures to move in the same way over time. An examination of the health of the older population, and particularly the trends in health status, needs to look at all dimensions and take into account their differing influences.

Of most interest to many of those interested in the wellbeing and care of the elderly is the extent to which health problems limit activity or create dependency. Commonly referred to as ‘disability’ this is an important indicator of the health and well-being of the older population. Verbrugge and Jette (1994) coined the term disablement process to describe the interrelationship of disease, functioning, and disability. In this model, diseases are seen as creating impairments that lead to limitations in physical functioning. For instance, arthritis may create joint stiffness which results in difficulty bending or grasping an object. When limitations are severe they may interfere with the ability to carry out specific activities, resulting in a disability. Environmental factors are an additional component of the process. Individuals may be able to adapt to their environment, or their task, to accommodate their limitations. In those cases, they may delay the onset of a disability. In this framework, physical limitations are seen as coming before disabilities and more closely related to the underlying disease process.

There are three different models describing how disability may change in the US population. The failure of success model, expressed by Gruenberg (1977) argued that with improvements in the treatment of some chronically disabling diseases the US would enter a period of a ‘pandemic’ of chronic diseases and disability. That is, it was expected that persons with chronic diseases, and the profound disabilities they can generate, would survive many more years raising the prevalence of chronic disability and the average amount of lifetime that could be expected to be lived in an impaired state (Verbrugge, 1984).

A second perspective, due to Fries (1980), postulated that a ‘compression of morbidity’ would occur as life expectancy reached a maximum (estimated to be about 85 years). As this survival limit was approached the age range at which deaths occurred would become smaller, leading to a rectangularization of the survival curve. However, Fries suggested, at the same time the age of chronic disease onset could become compressed. As a result, most of life would be spent in an unimpaired state.

The third model suggested that the times of chronic disabilities and diseases onset could be in a dynamic equilibrium with survival (Manton, 1982). In this model, specific diseases may be affected by healthcare advances in differing ways. These differences would affect the relationship between mortality and disability so that both total life expectancy and disability-free life expectancy could be increased. This type of change would decrease the average amount of time spent in disabled states.

While these theories attempted to explain population differences in healthy life expectancy, new developments in the field of aging and health have focused on the role of genetics in affecting healthy survival. It has been commonly observed that longevity clusters within families, those with long-lived parents and siblings are more likely to have a long life themselves. More recent studies have shown that the children of long-lived individuals, as well, have more favorable risk factor profiles and fewer age-related diseases (Newman et al., 2011). Despite the allure of finding a single ‘longevity’ gene, it is likely that several genes contribute to this effect, operating in many different ways. For instance, some genes may slow the aging process overall, while others may protect an individual from a particular disease.

Results from twin registry studies (Hjelmborg et al., 2006) and the Framingham Heart Study (Murabito and Lunetta, 2011) show that the genetic influences on longevity operate primarily above age 60. The heritability estimates for overall longevity range from 20 to 30%. The longevity phenotype, however, is very heterogeneous, including a wide range of physical and cognitive functioning levels. An examination of individual aging traits in the Framingham study shows varied heritabilities (Murabito et al., 2012). Physical frailty, for instance, showed a modest heritability, about 19%. But some less complex outcomes have higher heritability; measures of walking time and handgrip strength have substantial genetic contributions with heritabilities of nearly 40%.

Both individual and population measures of health provide important clues to the overall well-being of the older population and the outlook for future changes in health and functioning.

Mortality

Life expectancy itself is one important indicator of health status in a population and reductions in death rates are often used as an indication of improvements in health and well-being. Life expectancy at birth is 78.7 years in 2011; 81.1 years for US women; and 76.3 years for US men (Hoyert and Xu, 2012). The difference in life expectancy between men and women, now just under 5 years, has been declining since 1979, when the gap was nearly 8 years. There is a persistent racial gap in life expectancy as well, blacks have life expectancy of 75.3 in 2011 compared with 79.0 for whites.

More important as an indicator of late life health, however, is the life expectancy at age 65. For the total US population, life expectancy at age 65 has increased from 17.2 years in 1990 to 19.2 years in 2009 (Arias, 2012). White women have the longest expected survival, 20.3 years and black men the shortest, 15.8 years. In 2009 for the first time life expectancy at age 75 exceeds 10 years for all demographic groups, men and women, whites and blacks.

These gains in life expectancy reflect improvements in the underlying age-specific mortality rates. Between 1935 and 2010 death rates for persons aged between 65 and 74 fell by 62% (Hoyert, 2012). In the most recent decade, 2000 to 2010, the largest reductions in mortality occurred for males, with non- Hispanic black men experiencing the largest declines. All three major causes of death, heart disease, cancer, and stroke showed declines (Minino, 2013). Of growing importance for later-life health is the significance of Alzheimer’s disease (AD) as a cause of death. Mortality from AD has steadily increased during the last 30 years, becoming the fifth leading cause of death for people aged 65 and over (Tejada-Vera, 2013). Alzheimer’s disease accounts for between 5 and 15% of all deaths in older people. Some of this increase is due misclassification of AD into other categories leading to a significant undercounting of deaths attributable to AD. Changes in the coding of cause of death, in place since 1999, have allowed for estimation of a more consistent trend (Moschetti et al., 2012). Since Alzheimer’s disease is often preceded by many years of disability, the impact of this increase on health care and family costs is an important consideration for the future.

Disability and Functioning

Since disability is a major driver of health and personal care costs, tremendous effort in recent years has been expended on describing and documenting trends in disability levels in the older population. Disability is most often defined relative to the ability to live independently and take care of one’s personal care needs. The inability to perform the most basic activities, referred to as activities of daily living (ADLs), is considered the most severe form of disability. This standard set of activities includes bathing, dressing, eating, toileting, transferring from bed and chairs, and walking around inside. Less severe disability is measured by the inability to perform instrumental activities of daily living (IADLs), routine household tasks shopping, cleaning, cooking, and going places.

In his earlier discussion, Manton (2001) describes the US declines in functional disability first documented in the 1982 to 1989 National Long Term Care Surveys (NLTCS). The NLTCS are sets of longitudinally related surveys designed to assess changes in functional status, social conditions, and Medicare and LTC service use in the US elderly population. Through the 1990s, other US population studies found even larger declines than that first reported by Manton et al. (1997). Freedman and Martin (1998) using the 1991–1996 Survey of Income and Program Participation reported a decline which existed at the higher levels of disability and at advanced (85þ) ages. Waidmann and Liu (1998) also found confirmation of declines in the 1993–1996 Current Medicare Beneficiary Survey. Crimmins et al. (1997) found evidence for declines in the 1984 Supplement on Aging and the LSOA (longitudinal study of aging) from 1986 to 1990. Evidence of declines has been found in the 1985 and 1995 Supplements on Aging to the National Health Interview Survey (Crimmins and Saito, 2000). Evidence for declines in European countries was found in Waidmann and Manton (1998).

These various studies, while finding relatively consistent evidence of declines in limitations in IADLs and in functional limitations, produced mixed results on the trend in the most severe type of disability, limitations in ADLs. In an effort to summarize and harmonize the results of these studies a technical working group was formed in 2002, drawing together researchers with experience from five national data sets covering the US population: the Health and Retirement Study (HRS), the Medicare Current Beneficiary Survey (MCBS), the NHIS, the National Long Term Care Survey (NLTCS), and the Supplements on Aging (SOAs). The working group concluded that while evidence of a decline in activity limitations was mixed in the 1980s, by the mid-1990s there was a clear downward trend in reported limitations across surveys, despite differences in question wording and study design (Freedman et al., 2004). While this trend was most pronounced in limitations in IADLs and in functional limitations, from the mid- to late 1990s the proportion of the older population reporting difficulty in performing ADLs declined steadily, too.

This promising news, described as one of the most significant advances in the health and well-being of Americans in the past quarter-century (Schoeni et al., 2008), has been tempered by more recent evidence. In the most recent decades, since 2000, these trends appear to be changing. A recent summary (Freedman et al., 2013), carried out by many of the same researchers involved in the technical working group, compares results from four of the same national data sets covering the US population with the substitution of the National Health and Nutrition Examination Survey (NHANES) for the SOAs. All of these surveys cover the period 2000–08 and the NLTCS and MCBS allow analysis of both community and institutional populations. Carefully controlling for differences in question wording, coverage, and coding, trends in ADL and IADL limitations were estimated from each study. In contrast to the steady downward trend observed in the 1980s and 1990s, the more recent years of data show no change in the proportion of the older population reporting difficulty in performing these personal care and household activities.

More alarming than the apparent stalling in improvement in functioning at older ages is evidence that health at younger ages, those aged 50–64, is not improving and, perhaps, declining. Analysis of the NHIS (Lakdawalla et al., 2004) found that between 1984 and 1996 there was an increase in needs for help among those in middle age, although the numbers were small. Using the Behavioral Risk Factor Surveillance Survey (BRFSS), Zack et al. (2004) found an increase from 1993 to 2001 in those in middle age reporting poor or fair health. Worsening functioning and health were observed from 1992 to 2004 in the HRS (Soldo et al., 2007) for younger cohorts. Examining a variety of health measures, Martin et al. (2009) conclude that trends for the Baby Boom generation vary by measure, period, and age group. For mortality and self-reported health, baby boomers are doing better, while trends for functional limitations and the need for IADL help are stable. Other analyses find that the proportion of people aged 50–64 who report needing help with personal care, while small, increased between 1997 and 2007 (Martin et al., 2010b).

Disease Prevalence

During the period while mortality rates were falling and disability was clearly declining, prior to 2000, the prevalence of most chronic diseases increased. Between 1984 and 1994 increases in self-reports of arthritis, heart disease, cancer, diabetes, stroke, and osteoporosis were observed in the population aged 70 and older (Crimmins and Saito, 2000; Freedman and Martin, 2000). Manton et al. (1995) observed that some conditions decreased from the 1980s to the 1990s (arthritis, circulatory, and cerebrovascular conditions), while others increased (pneumonia, bronchitis, and diabetes).

In more recent time periods, after 2000, the prevalence of chronic diseases continued to increase in the older population. Importantly, musculoskeletal conditions, like arthritis, which have strong links to functional impairments and disability have shown increases. During the time period, 1997–2004, continuing increases in the prevalence of arthritis, cancer, diabetes were reported in the NHIS, although no significant change was observed for heart disease, stroke, or lung conditions (Freedman et al., 2007). This trend is observed in younger cohorts, too. Among those aged 50–64 an increase in musculoskeletal conditions are the most commonly cited causes of disability (Martin et al., 2010b). Unclear is the effect of cognitive impairments on the disability trends. While the prevalence of Alzheimer’s disease has increased, the contribution of this condition to overall disability is harder to measure in our large national surveys due to proxy respondents and the greater likelihood of institutionalization.

Not only has chronic disease prevalence increased, but the likelihood of reporting two or more chronic conditions has increased in recent years. Analysis of data from the NHIS shows that among those aged 65 and over the proportion of those reporting two or more chronic conditions (defined as hypertension, heart disease, diabetes, cancer, stroke, chronic bronchitis, emphysema, asthma, or kidney disease) increased from 37 to 45% between 2000 and 2010 (Fried et al., 2012). The most common combination was hypertension and heart disease (21%) but one of the biggest increases was seen in the percentage with both hypertension and diabetes; an increase from 9 to 15% over the 10-year period. These increases occurred for both men and women and for all racial groups.

Causes of Disability Trends

The reasons for the decline in disability observed during the close of the twentieth century and the reasons for the more recent stagnation in improvement remain unclear. The increased prevalence of chronic diseases in tandem with disability declines indicates some possible explanations (Schoeni et al., 2008). One theory is that the earlier diagnosis of chronic conditions has led to higher disease prevalence at a stage before impairments are evident. Furthermore, earlier treatment of chronic conditions may postpone the debilitating effects of the disease. Better medical treatments and improved drug therapies may make diseases less disabling.

The use of assistive devices and accommodations is another possible explanation for the seeming paradox of increased disease and decreased disability. To the extent that disability is a function of both personal abilities and the environmental context in which activities are performed, changes in the environment alone may reduce reported disability. The IADLs, which saw the largest decline, could have been influenced by changes in the socioeconomic environment which allow changes in socially defined gender roles (e.g., men doing more grocery shopping or laundry).

The reversal of the trend in disability improvement is very new and likely to engage the attention of researchers in the coming decade. Trends in obesity are often cited as a primary driver of the reversal and may operate through diabetes, arthritis, and heart conditions (Sturm et al., 2004), but others attribute less of the increase directly to obesity (Martin et al., 2010a). The past improvements may have reflected a change in the disablement process, particularly the use of technology and assistive devices (Schoeni et al., 2008). Future declines in disability may require even newer technologies if we have reached a saturation of the use of these devices or run up to the limits of their ability to compensate for functional changes. The lack of health improvements in the cohorts soon to reach advanced age, coupled with the larger size of these age cohorts, may signal a costly reversal of past trends in the older populations need for care.

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