In this large study of women, we documented a strong, positive association between mid-life leisure-time physical activity and the odds of successful survival, or exceptional overall health in later life. This included a positive relation between moderate-intensity activity, such as walking, and odds of maintaining overall health status among aging women.
There is persuasive evidence supporting an inverse association between physical activity and many individual aspects of health, including multiple chronic diseases, cognitive function, physical function, and mental health.9–19, 34
However, fewer epidemiological studies have examined the association of physical activity with overall health status as evaluated by multiple domains among those who have survived to older ages. In addition, existing data are primarily for men,3, 5, 7
despite the fact that women live, on average, longer than men. Among Cardiovascular Health Study participants and male Harvard college alumni, mid-life physical activity was associated with an improved overall health status at older ages.3, 7
In contrast, among male Japanese Americans, mid-life physical activity was not associated with the probability of exceptional overall health at older ages.5
In the latter study, adjustment of risk factors that can mediate the effects of physical activity on human health, such as plasma glucose, plasma triacylglycerol, hypertension, and BMI, is likely one explanation for the null association. Despite this, it is difficult to directly compare our findings to these studies, since our cohort only included women, for whom physical activity patterns tend be different from those among men. Nonetheless, similar to the Cardiovascular Health Study and the Harvard alumni study, we observed a strong, positive association between physical activity and exceptional survival at ages 70 years and older in women. Our observations are also compatible with previous studies that used disability-free survival or self-rated overall health as a surrogate measure of successful survival.20, 21
In the previous studies of successful survival, walking was not distinguished from more vigorous activities. While approximately 85% of Americans do not participate in any regular vigorous physical activities, 44% walk for exercise.35
Consistent with the literature on walking in relation to chronic diseases and other specific, adverse health outcomes,36–38
our results suggested that energy expenditure from walking at moderate to brisk pace could also increase the likelihood of exceptional survival. Our observations provide initial support for the consideration of walking in broad public health recommendations, since walking is sustainable and can often be easily incorporated into people’s daily schedule.
Importantly, in the current study, being physically active was associated with increased odds of successful survival for both lean and overweight women. This observation was consistent with our previous findings that physical activity was related to a substantial reduction in risk of chronic diseases and premature death among participants with various body weights.10, 34, 39
Together, our data strongly support the notion that, regardless of body weight, engaging in physical activity may increase the probability of preserving an optimal health status. Meanwhile, our study also demonstrated that maintaining a healthy body weight and high physical activity levels simultaneously at mid-life likely convey the highest odds of successful survival.
The strengths of the current study include a comprehensive measurement of overall health of aging women, large sample size, high follow-up rate, accurate self-reported incidence of chronic diseases, and validated methods to quantify physical and mental disabilities and cognitive function. Further unique aspects of our study are the focus on women, who live longer than men on average, and thus merit particular attention in considering risk factors for successful survival, as well as the examination of walking, one of the more common types of activity in women. An additional strength is the multiple analyses conducted to consider possible reverse causation. For example, we excluded anyone with existing chronic diseases at baseline, and also imposed an average 14 year lag period between exposure and outcome assessments – to both address reverse causation as well as the biologic likelihood that health and chronic conditions at older ages are influenced by lifestyle factors adopted at younger ages.
Our study also has several limitations. First, the generalizability of the current study may be limited to women who had primarily European ancestry and were largely healthy at mid-life. Further research should be conducted in minority populations and populations with various specific health issues at earlier life. In addition, we considered successful survival as of age 70 years. Whether the observed associations can be generalized to populations at much older ages is unknown. Second, although our questionnaire to measure physical activity has been validated in a similar population and showed reasonable accuracy, the self-reported physical activity levels were inevitably subject to measurement error. However, since these data were collected before any of the study outcomes occurred, the measurement errors would most likely be non-differential and bias true associations to the null. Third, as in any observational study, residual confounding is also an alternative explanation of our observations. However, the strength and the dose-response gradient of the multivariate associations support a causal relationship between physical activity and successful aging. In addition, the homogeneity of our study population with respect to demographic characteristics and access to health care further reduce possibilities for confounding. Fourth, we did not assess physical and mental health status at baseline. Long-term physical impairment or mental limitations may, thus, bias our observations. However, when we restricted our analysis to women with sufficient function to engage in at least low to moderate physical activity levels at baseline, we observed similar associations. Lastly, approximately 16% of eligible women were excluded from the current analysis because of missing physical activity data at baseline. These participants had slightly higher BMI and worse physical, cognitive, and mental status at older ages, and were less likely to be active at baseline than women who provided data on their physical activity. This combination could lead to bias towards the null.
In summary, the current study provides new evidence that mid-life physical activity, including walking, is associated with increased odds of exceptional health among women who are initially healthy at mid-life and survive to older ages. Since the American population is aging rapidly2
and nearly a quarter of Americans do not engage in any leisure-time activity,40
our findings appear to support federal guidelines regarding physical activity to promote health among older people and further emphasize the potential of activity to enhance overall health and well-being with aging. The notion that physical activity can promote successful survival rather than simply extend the lifespan, may provide particularly strong motivation for initiating activity.