By Barbara Sternfeld, Ph.D., FACSM
More than three decades ago, James Fries published a seminal paper in the New England Journal of Medicine that predicted an expansion of the years of healthy, active life as a result of a delay in the onset of chronic disease and disability that would be greater than increases in overall life expectancy. He labeled this demographic shift the compression of morbidity. To those of us following in the steps of Drs. Jeremy Morris and Ralph Paffenbarger, Jr. in the then-emerging field of physical activity epidemiology, the compression of morbidity was a compelling hypothesis. Accumulating evidence for the role of physical activity in protecting against the major causes of morbidity and disability, such as coronary heart disease, hypertension, diabetes and some cancers, suggested that the lifetime burden of illness in the population could, indeed, be shortened by widespread adoption of regular physical activity.
Since then, much demographic analysis and debate has focused on trends in morbidity and mortality and whether there is evidence for compression of morbidity. In 2011, Crimmins and Beltran-Sanchez examined age-specific disease prevalence and mobility-related functional status from 1998 to 2006. They based their analyses on data from the National Health Interview Survey, along with age-specific mortality rates from official U.S. life tables for the same years. The data showed a slight increase in overall life expectancy over this interval, but also a decrease in life expectancy free of disease or functional impairment. This result was due, perhaps in large part, to the increase in obesity in recent years. Those authors concluded that there had been an expansion, rather than a compression, of morbidity. Despite other analyses, with evidence supporting the compression of morbidity, Crimmins and Beltrans-Sanchez argued that this finding is largely because others have focused on severe disability, such as inability to perform activities of daily living, rather than functional impairment, such as ability to walk across the street before a traffic signal changes. Medical advances, they argued, have made chronic diseases both less lethal and less disabling, yet those conditions continue to impact higher-level functioning, often at younger ages.
Our study, published in MSSE, has direct relevance for this discussion. Using 14 years of data from SWAN (Study of Women’s Health Across the Nation), a population-based, multi-racial/ethnic cohort of midlife women, we showed that a healthy lifestyle score, consisting of regular physical activity, a healthy diet and abstention from tobacco, measured over as many as nine years during midlife, was positively associated with better physical performance, measured at least four years later in older midlife. The domains of physical performance that were associated with a healthy lifestyle were walking speed and repeated chair stands (a measure of lower body strength and endurance). Most striking, these associations were due entirely to physical activity. Although a healthy diet and abstention from smoking clearly have obvious health benefits, regular physical activity in midlife appears to be the key determinant of better mobility-related physical function in late midlife, at least for women.
These findings strongly imply that physical activity can contribute to the expansion of life expectancy without functional impairment and, effectively, bring about the achievement of the compression of morbidity that Fries envisioned several decades ago. The challenge, of course, remains the relatively modest proportion of the population that regularly engages in physical activity. Although ACSM has been a leader in the efforts to promote physical activity, much more work in this area is still needed — particularly now, at a time when public health resources are expected to be stretched even further than they have been. It is imperative that we in ACSM do what we can to ensure that all segments of the population lead healthier, active lives.
Barbara Sternfeld, Ph.D., FACSM, is an emeritus research scientist at the Kaiser Permanente Northern California Division of Research in Oakland, California, where she began her career in 1985. Dr. Sternfeld’s training is in epidemiology and exercise science. She has extensive experience with large, prospective cohort studies, most notably, the CARDIA study (Coronary Artery Risk Development in Young Adults), and SWAN (Study of Women’s Health Across the Nation). Her research interests, largely focused on women’s health issues, include longitudinal analyses of physical activity and health outcomes, methods for assessment of physical activity and intervention trials.
This commentary presents Dr. Sternfeld’s views on the topic of a research article that she and her colleagues authored. That article appeared in the February 2017 issue of Medicine & Science in Sports & Exercise® (MSSE).
Viewpoints presented on the ACSM blog reflect opinions of the authors and do not necessarily reflect positions or policies of ACSM.