Will longer life feature chronic disease and disability?
Or will it postpone chronic disease and disability?
According the Stanford University researcher James Fries, the compression of morbidity (chronic illness and disability) occurs if the chronological age at first appearance of aging manifestations and chronic disease symptoms increases faster that life expectancy. If the above is true, major illnesses will be “compressed” into the last few years of life. The result is a greater proportion of life years lived without major limitations. Dr. Fries proposed the compression of morbidity hypothesis in 1980. Over the years, Fries and colleagues have published articles supporting this concept.
Fries and his colleagues studied men and women members of a running club in California. Club members were age-matched with non-running community members. Answers on the Health Assessment Questionnaire measured disability for all participates. Over an eight-year period, the disability of both the women and men in the control group diverged significantly from that of the women and men runners. Disability of the runners increased only between ages 75 and 79. The mortality for runners was significantly lower that of the controls, resulting in an estimated two years of extra longevity for the runners. Exercise appears to be a key aspect of prolonging a disability-free life.
A longitudinal study of 1,741 graduates of the University of Pennsylvania that began in 1939 and 1940 supported the compression of morbidity hypothesis. Health risk factors included body-mass index, smoking, and exercise. Mean disability of subjects in 1986 was low (0.06). Survivors in the low-risk group had half the disability risk (0.45) of the survivors in the high-risk group (0.91). The onset of disability was postponed for about 5 years for survivors in the low-risk compared to the high-risk group. Long-term exercise can limit health risks, resulting in both longer life span and longer health span.
The study by James Fries and colleagues of members of the running club in California that began in 1984 continued over a 13-year period until 1997. The runners were matched with non-runners as a control group. After 13 years of follow-up the runners fared far better that the controls in terms of incident disability. At each year during the study, the risk of disability, regardless of its severity, was significantly lower along the runners compared to the controls. Depending of the level of disability, the likelihood of it occurring was postponed by 5.5 – 13.7 years for the runners compared to the controls. Plus, the difference increased over time. After 13 years when the average age of the runners was 72 years, the risk of dying was 64 percent lower for members of the running club than for the controls. Running and other aerobic activities reduced the risk of premature death and increased the length of a disability-free life.
Little doubt remains that physical exercise promotes a range of health benefits. Most authorities recommend 30 minutes of moderate exercise on most day of the week. But does the benefit of exercise persist into older age? If so, does exercise reduce the risk of disability? And what about strenuous exercise? Do most of us need to worry about overdoing physical exercise?
In 1984, researchers at Stanford University recruited people in the nationwide 50+ Runners Association Club (age 50 or older) plus persons at Stanford who served as controls. Twenty-one years later, the researchers studied 284 runners and 156 controls. Mortality data were obtained for all the original participants. The self-administered Health Assessment Quality Disability Index evaluated disability. In 1984, runners were younger and leaner than controls. The disability index for controls exceeded that for runners at all time points and increased for both groups with age, but at less than half the rate for runners (0.17) versus controls (0.36). At 19 years of follow-up, 15 percent of runners had died compared to 34 percent of controls. After statistically adjusting for potentially confounding factors, the mortality risk of runners was 61 percent of that of controls. Disability and survival curves continued to diverge between groups after 21-years of follow-up as subjects neared 80 years of age. This study indicates that vigorous exercise (running) at middle and older ages predicts reduced disability and greater survival late in life.
The compression of morbidity hypothesis predicts that seniors with healthier lifestyles will live longer and have less cumulative disability that those with less healthy lifestyles. University of Pennsylvania Alumni Study (see above) and the Runner Study (see above) both provide convincing support for compression of morbidity hypothesis.
The National Long-Term Care Survey and the National Health Interview Study both found declining disability in the US from 1982- 2004 and 1982-1999, respectively. Over the same time periods, longevity in the US increased. Thus, compression of morbidity occurred spontaneously without a national policy promoting it. James Fries and colleagues suggested a four-part national policy: 1) Primordial Prevention (never smoking, never obese, never sedentary); 2) Primary Prevention (increasing exercise, reducing smoking, moderating other health risks); 3) Medical (reducing hypertension, diabetes, reducing time to first heart attack); 4) Tertiary Prevention (joint replacements, cataract operations). Start at the top of the list and work down.
Active aging is a consequence of compression of morbidity – postponing functional decline more than postponing mortality decline. In other words, functional life span increases faster than actual life span (thereby lengthening Quality of Life Span). Studies to date generally support the compression of morbidity hypothesis with a few exceptions in some populations. The Runners Study, begun in 1984, followed 523 senior runners (average age 58) and a control group of age-matched non-runners. Data analysis controlled for a host of potential confounding factors. Over the years through an average age of 80, the differences in disability between the runners and non-runners grew steadily greater.
Postponement of mild (0.1 unit) and moderate (0.2 unit) disability for runners compared to controls was 14 and 16 years, respectively. Runners also enjoyed longer lives that non-runners. At year 25, runners had 60 percent of the mortality of non-runners. In the University of Pennsylvania Alumni Study, 1741 alumni followed from the classes of 1939 and 1940. Study formed three cohorts when subjects were 43 years old on average. Risk factors were 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 (zero risk factors) had average disability of 0.32. Subjects with low risk postponed moderate disability (score 0.3) 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 studies showed greater postponement of disability than extension of life span, thus supporting the compression of morbidity hypothesis.
The Chicago Heart Association Detection Project in Industry offered an opportunity to determine if favorable cardiovascular health in middle-age predicted lower risk of chronic disease later in life. Would reduced illness translate into lower medical care costs after age 65? Researchers at Northwestern University used data from 25,804 participants with an average of 44 years at baseline and who reached age 65 by 2010. Ratings of five factors (blood pressure, cholesterol, type 22 diabetes, body-mass index, and smoking) categorized cardiovascular health into four categories: 1) favorable levels of all factors, 2) no high risk factors but with one or more elevated risk factors, 3) one high risk factor, and 4) two or more high risk factors.
Participants with favorable health at baseline lived almost four years longer and delayed the onset of all-cause chronic illness and cardiovascular illness by 4.5 and 6.9 years, respectively, compared with participants with two or more high-risk factors. Cardiovascular health in middle-age predicted lower risk of chronic disease up to 43 years later. Furthermore, favorable cardiovascular health at age 65 translated into lower cumulative ($17,863) and annual ($5,458) Medicare and associated supplemental costs compared to having two or more high risk factors. This study supports the compression of morbidity hypothesis.
If you want to achieve exceptional aging, you'd do well to maintain your current program of physical activity for the rest of your life. Or if you don't have a program, start one and stick with it. You'll be more likely than the couch potatoes to avoid chronic diseases or at least postpone them until late in life.