Will greater longevity lead to lower quality of life due to chronic diseases, frailty, and disability?
James Fries, a researcher at Stanford University, thought that seniors with healthier lifestyles would live longer yet have less cumulative disability than those with less healthy lifestyles.
Beginning in 1984, Fries and his colleagues studied 523 men and women members of a running club in California. Club members with an average age of 58 were age-matched with non-running community members. Data analysis controlled for a host of potential confounding factors. Over an eight-year period, the disability of both the women and the men in the control group diverged significantly from that of the women and men runners. Disability of the runners didn’t increase until age 75 and 79. The mortality for runners was significantly lower than that of the controls. The runners enjoyed an estimated two years of life compared to non-runners. Physical exercise appeared to be a key aspect of prolonging a disability-free life. The idea that healthy living could compress disability and disease into the last few years of life became known as the Compression of Morbidity hypothesis (Fries 1996).
Over a decade later, Fries and his colleagues updated the Runners Study. Up to an average age of 80, the differences in disability between the runners and non-runners grew steadily greater. Runners postponed mild (0.1 unit) and moderate (0.2 unit) disability 14 and 16 years, respectively. Compared to non-runners. At year 25 of the study, runners had 60% of the mortality of non-runners (Fries 2012).
Fries and colleagues also used data from the University of Pennsylvania Alumni Study to test the Compression of Morbidity hypothesis. Alumni (N=1,741) from the classes of 1939 and 1940 were followed beginning when subjects were an average of 43 years old. The researchers identified three risk factors for disability: current smoking, body mass index (25 or higher), and absence of vigorous physical activity. In year 2005 (average age 86), subjects with high risk (three factors) had average disability of 0.63, while the subjects with low risk (0 risk factors) had average disability of 0.32. Subjects with low risk postponed moderate disability (score 0.3 or higher) for an average of 10 years compared to subjects in the high-risk group. Subjects in the low-risk group lived longer than subjects in the high-risk-group.
Both the updated Runners Study and the University of Pennsylvania Alumni Study showed that the life span of runners increased relative to non-runners or high-risk persons. But the length of a disability-free life for runners or low-risk persons increased even more. These results support the Compression of Morbidity hypothesis (Fries 2012).
The accompanying figure illustrates two hypothetical situations. The lower curve depicts the dramatic loss of function over time for a person in the “business-as-usual” category. The upper curve depicts the minimal loss of function for a person with healthy habits. For those who develop healthy habits, disability likely occurs only in the last few years of life. Which curve will you choose? If you want to live longer and better, develop the healthy habit of regular physical exercise.
Fries, JF. 1996. Physical activity, the compression of morbidity, and the health of the elderly. Journal of the Royal Society of Medicine 89:64-68.
Fries, JF. 2012. The theory and practice of active aging. Current Gerontology and Geriatrics Research. Article ID 420637