In the coming decades, the number of older adults in the United States will reach an unparalleled level. Because of the high prevalence of potentially preventable health problems in the older population, efforts to promote health among older adults have been encouraged (e.g., Morely & Flaherty, 2002
; Rowe, 1999
). There is as yet no consensus among researchers in gerontology, however, as to the definition and measurement of “healthy” aging.
In this investigation, we examined one of the most prominent conceptualizations of healthy aging, Rowe and Kahn’s concept of successful aging. Results of this study indicate that no greater than 11.9% of older adults experienced successful aging in any year. This estimate is lower than the 18.8% observed by Strawbridge and colleagues (2002)
in their examination of Rowe and Kahn’s concept among participants of the Alameda County Study. Reasons for the discrepancy likely include differences in sample composition (e.g., the percentage with at least a high school education was higher among the sample of Strawbridge et al.) and variation in the assessment of each of the three main components of Rowe and Kahn’s concept (e.g., number of items used to assess physical functioning). Despite these differences, however, both studies suggest that the vast majority of older adults do not meet Rowe and Kahn’s definition of successful aging.
The prevalence of successful aging varied by demographic factors, with the unadjusted odds of successful aging lower among those of advanced age, non-White race, and lower SES. In general, these findings correspond with demographic differences reported by Strawbridge and colleagues (2002)
. One exception is gender. Whereas we observed little gender difference in unadjusted analyses, Strawbridge and colleagues found that a substantially higher percentage of women than men met Rowe and Kahn’s definition. As with the overall prevalence, this discrepancy undoubtedly reflects differences in the measurement of successful aging (e.g., house cleaning was incorporated as a productive activity in their study, but not ours) and sample composition. Our results also correspond with a recent British study in which SES was found to play a significant role in successful aging (Britton et al., 2008
Several findings from our comparison of successful aging across demographic subgroups warrant additional discussion. The first concerns gender differences in successful aging. Although we found no significant gender difference in the unadjusted analysis, men had lower odds of successful aging after controlling for other demographic factors. Given that women typically report more chronic conditions than men, have more functional limitations, and experience more disability (Newman & Brach, 2001
), this finding may seem somewhat counterintuitive. At least two factors help explain this finding: gender differences in characteristics such as age and SES and our chronic disease criterion.
As has been discussed widely (e.g., Calasanti & Slevin, 2001
), older women are typically more socioeconomically disadvantaged than older men. In addition, women comprise a greater percentage of the oldest age categories (He et al., 2005
). Given that lower SES and advanced age increase the risk of poor health, controlling for these factors should reduce gender differentials in health. This is not the whole explanation, however. More specifically, our decision to include only those chronic conditions that are major causes of death, some of which occur more frequently among men than women (e.g., cancer, heart disease; He et al.), influenced the observed relationship between gender and successful aging. Post hoc analyses revealed that if we had included freedom from arthritis and hypertension (two conditions for which the prevalence is greater among women than men; He et al.) in our chronic disease criterion, differences between men and women would not have been statistically significant in any wave. This highlights an important point raised by other scholars (e.g., Phelan & Larson, 2002
) that how one defines successful aging affects observed associations.
The second finding of interest pertains to SES. Corresponding with the general finding that those of higher SES experience better health (see, e.g., review by Adler et al., 1994
), we found that the odds of aging successfully increased substantially for those with higher levels of education, income, and wealth. Notably, significant differences remained for each indicator after simultaneously controlling for the other measures of SES. This undoubtedly reflects, in part, the unique ways in which each component of SES affects health and opportunities for successful aging. Whereas higher income, for instance, permits greater access to health promoting resources (Galobardes, Shaw, Lawlor, Davey Smith, & Lynch, 2006
), the cognitive resources (e.g., knowledge, capacity for problem solving) garnered through higher education may foster a sense of control that results in better health practices (Mirowsky & Ross, 2003
). It is also possible, however, that the categorization schemes used for the various SES indicators resulted in imperfect statistical control, leaving all three indicators significant in adjusted analyses. A finer categorization scheme for wealth, for example, may have weakened the association between income and successful aging in this largely retired sample of older adults.
The third finding pertains to the observed racial-ethnic disparities in successful aging. In unadjusted analyses, we found that non-Whites were substantially less likely to be classified as aging successfully than their White counterparts. After adjusting for covariates, however, differences were reduced and were no longer statistically significant for three of the four waves. As has been observed by others (e.g., Hayward, Crimmins, Miles, & Yang, 2000
), post hoc analyses revealed that SES played an important role in racial-ethnic differences in successful aging. More specifically, when just age and gender were controlled, the odds of successful aging remained markedly lower for non-Whites in all waves. It was only when SES was controlled that the effect of race diminished. As noted by House and Williams (2000)
, however, “racial/ethnic status is a major determinant of every indicator of socioeconomic position” (p. 88). Thus, the attenuation of effect that occurs when SES is controlled should not be interpreted to mean that race and ethnicity do not have an impact on successful aging.
Lastly, we observed a decline in the prevalence of successful aging during the 6-year period examined in this study. An examination of the components of successful aging suggests that the decline in prevalence is due to a decrease in the number of older adults meeting the disease and physical functioning criteria. The former finding is consistent with literature documenting a rise in the prevalence of at least some chronic diseases in the older population (e.g., Crimmins, 2004
; Freedman & Martin, 2000
; Freedman, Schoeni, Martin, & Cornman, 2007
). The latter finding, however, is inconsistent with reported declines in functional limitations among older adults (Freedman, Martin, & Schoeni, 2002
). This discrepancy may reflect differences in the time periods covered (the 80s to mid-90s vs the 6-year period between 1998 and 2004) or differences in the assessment of physical functioning. Because our focus was on the identification of individuals with “high physical functioning” as opposed to quantifying population-level changes in functional limitations, we did not include several basic tasks (e.g., “sitting for about two hours”) in our operationalized definition.
Several study limitations should be noted. To start, the measures of active engagement used in this study only superficially capture this component of Rowe and Kahn’s definition. Specifically, our assessment of productive engagement was limited to just three activities: working for pay, formal volunteerism, and caring for grandchildren. Clearly, there are other activities that fall within the realm of productive activity that are not captured here (e.g., helping a homebound friend with errands). The social relations component was also assessed in a less than ideal manner. In this investigation, we considered whether an individual was married, had a good friend nearby, and how frequently he or she visited with neighbors. Although more than 90% of participants met one or more of the three criteria (data not shown), other important relationships (e.g., parent–child) and social activities (e.g., church attendance) were not examined and level of social support was not assessed directly. Given these limitations, our findings with respect to active engagement should be viewed tentatively. It should be noted, however, that even if 100% of participants had met the engagement criterion as fully conceptualized by Rowe and Kahn, less than one fifth of the older population would have been classified as aging successfully in all years. Nevertheless, more precise estimates could be obtained with better measures of social relations and productive engagement.
Second, it is important to reiterate that how one chooses to measure successful aging affects prevalence estimates and observed relationships. In this investigation, for example, the only chronic diseases included were those that are major causes of death among older adults. Had we also included hypertension and arthritis, the estimate of successful aging would have been lower, as these conditions affect roughly half of all older adults (Federal Interagency Forum on Aging-Related Statistics, 2006
). Moreover, demographic relationships would likely be different from what was observed here, as disease profiles vary by age, gender, race, and SES.
Third, interactions among demographic factors were not examined in this study. Given that each demographic status is associated with unique advantages and disadvantages over the life course, it is entirely possible that the effect of one status (e.g., gender) on successful aging varies by level of another status (e.g., race-ethnicity). Where possible, interactions among demographic factors should be examined in future studies of successful aging.
Fourth, this investigation does not incorporate those older adults who required proxy respondents and those residing in nursing homes. Had they been included, prevalence estimates would undoubtedly be lower, as these subgroups typically have worse health. Moreover, their inclusion may alter the pattern of successful aging observed over time.
Lastly, although HRS is a longitudinal study, the associations among demographic factors and successful aging examined in this study were cross-sectional in nature. Thus, care must be taken with respect to assumptions about causality, particularly for factors such as income and wealth for which health problems may precipitate declines in financial resources (e.g., Kim & Lee, 2006
This investigation has several important implications for those interested in studying healthy aging. First, the small percentage of adults meeting Rowe and Kahn’s definition suggests that it is too rigorous for use as a benchmark for measuring and monitoring the health status of our older population. Although it has moved into broader realms, the original intent of Rowe and Kahn’s concept was to encourage the recognition and study of those with unusually good health for the purpose of deepening our understanding of age-related changes in health and factors responsible for the maintenance of unusually good health in older adulthood (Rowe & Kahn, 1987
). For such purposes, a strict definition of successful aging is understandable. For broader public health purposes, however, this study suggests that a less rigid definition is needed. It is worth noting that if we had operationalized Rowe and Kahn’s definition to the fullest extent (e.g., incorporated a larger number of diseases as well as risk factors for disease), the prevalence of successful aging would have been even lower. The problem with too rigid a definition is that individuals with relatively inconsequential disease and/or impairments are likely to be classified as being in an unhealthy state. This is not desirable when attempting to identify individuals who would benefit from public health intervention.
In a discussion of disability, Mehlman and Neuhauser (1999)
note that “the best definition of disability may be one that is the best predictor of something important” (p. 386). This is a useful guide for definitions of successful aging as well. For those interested in modifying or refining Rowe and Kahn’s definition, a critical next step will be to determine what that “something important” is. This is not an easy task, however, as what is deemed important will depend on who is asked. Strawbridge and colleagues (2002)
, for instance, examined how well two methods of measuring successful aging related to psychological well-being. Other scholars from other disciplines might be more concerned with how well definitions correlate with outcomes such as active life expectancy or health service utilization. Older adults may utilize yet another benchmark (e.g., the ability to engage in desired activities). Furthermore, there is likely to be considerable within-group variation in what is felt to be important. With respect to older adults, for example, Phelan and Larson (2002)
have noted that factors such as age, birth cohort, and race-ethnicity may influence beliefs about what it means to age successfully. In the end, it may be that a single definition of successful aging is neither practical nor possible, but must vary with the context in which it is used. At a minimum, however, researchers can explain how their definition relates to “something important” and acknowledge the standards or values by which it was deemed “important.”
Second, the results of this investigation clearly demonstrate that successful aging varies along socially defined statuses, supporting the calls of scholars such as Riley (1998)
for greater recognition of the importance of broad structural factors in successful aging. They also highlight a continued need for public health efforts aimed at the elimination of health inequalities by race-ethnicity and SES.
Finally, the decline in the prevalence of successful aging across time warrants attention. Analyses suggest that it is due largely to a drop in the number of older adults meeting the disease and physical functioning criteria. Given that chronic disease and functional difficulties can negatively affect quality of life, potential reasons for the observed changes should be explored.
Few older adults meet Rowe and Kahn’s definition of successful aging, although the percentage varies by factors such as age, education, and income. Although a rigid definition of successful aging may be appropriate for some purposes (e.g., to study predictors of phenomenal health and functioning), findings suggest that modification of Rowe and Kahn’s concept is necessary if it is to be used as a benchmark by which to assess the health and functioning of our older population. In its current form, we are likely to classify many older adults with good health and functioning as being in an unhealthy state for what may be relatively minor reasons. A first step will be to determine exactly what it is that we hope to achieve by promoting successful aging. Only then can we determine how best to define and measure the concept.