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Invited Commentary
Sep 24, 2012

Thriving of the FittestComment on “Fitness and the Development of Chronic Conditions in Later Life”

Author Affiliations

Author Affiliation: Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, Bethesda, Maryland.

Arch Intern Med. 2012;172(17):1340-1341. doi:10.1001/archinternmed.2012.3406

In 1980, James F. Fries, MD, published his seminal thesis on the limit of the average human life span—which he pinpointed at 85 years—and the compression morbidity into the final period of life, which he offered as both observation of a societal trend and a public health goal.1 He whimsically invoked this ideal by citing a poem by Oliver Wendell Holmes Sr about a “one-hoss shay,” a carefully constructed carriage that functions beautifully and then breaks down “to pieces all at once” after exactly 100 years. Fries contrasts this vision to the notion that ever-increasing life span afforded by improvements in public health and medicine would lead to increasing proportions of the population spending many of their final years with significant infirmity. Fries and his colleagues2 have continued to find evidence for the compression of morbidity and the “rectangularization” of the survival curve.

The concept of healthy or “successful” aging, once considered almost an oxymoron, was introduced in the 1960s and 1970s and has since been an area of active investigation. Healthy aging has been found to be related to several lifestyle factors, including abstinence from smoking, physical activity, maintenance of weight within normal ranges, and moderate alcohol consumption.3 In recent years, clues to the genetics of longevity have begun to emerge,4 and genetics undoubtedly plays an important role in maintaining good health as well as avoiding disease. Several studies5 have also found that cardiorespiratory fitness measured at a single time is strongly associated with both longevity and reduced risk of chronic disease, particularly cardiovascular disease, and is a better predictor than physical activity levels, likely, in part, because of the objectivity of the measurement and ability to capture the cumulative effects of exercise.

Willis and colleagues6 provide further evidence for physical fitness as a contributor to healthy aging and the compression of morbidity. By linking the large clinical database comprising men and women who visited the Cooper Clinic from 1970 to 2009 and underwent standardized treadmill fitness testing to Medicare claims when they reached age 65 years or older, the authors identified 18 670 persons who were free from chronic disease at the time of their examinations and were covered by Medicare from 1999 to 2009. After adjusting for age, body mass index, systolic blood pressure, total cholesterol level, smoking, fasting blood glucose level, and alcohol intake, there was a strong graded relationship of fitness to the rate of development of a set of common chronic conditions, including ischemic heart disease, congestive heart failure, stroke, diabetes mellitus, chronic obstructive pulmonary disease, chronic kidney disease, Alzheimer disease, and colon or lung cancer. The authors found an approximate 6% reduction in the risk of a chronic disease for every MET achieved, with a range of 5 to 6 METs across quintiles of fitness or an approximate doubling of risk between quintiles 1 and 5. This relationship was robust and similar when individual diseases were eliminated from the common set of conditions. Fitness appeared strongly protective against each condition, and there were similar relationships in men and women.

Furthermore, in an analysis of 2406 decedents, there was a clear relationship between fitness and the proportion of the final 5 years of life spent with a chronic condition. The highest of 3 fitness groups spent approximately 50% as much time with 4 or more chronic diseases as the lowest fitness group and 34% more time with no or 1 chronic disease.

Fitness may be a key to healthy aging, but the interpretation and translation of the findings of this article require some caution. First, there is only one behavior that leads to increased cardiorespiratory fitness (not counting taking anabolic steroid supplements, which improve muscle mass but may not improve fitness in healthy men): exercise. Yet, fitness is a function of both exercise and genetics.7 Because genetics likely plays a role in longevity and certainly plays a role in disease avoidance, if some of the same genes are involved in longevity and fitness, they may serve as major confounders in the attractive interpretation that exercise leads to fitness, which leads to healthy aging. Second, as readily acknowledged by the authors, people who visit the Cooper Clinic and compose the group studied are generally well educated, and approximately 98% are white. In addition, this cohort was leaner and likely more fit than the average American of today. It is possible that the findings from the present study would be dramatic with a broader range of body mass index, socioeconomic status, and ethnicity. Still, the authors are to be commended for using this unique database and taking advantage of Medicare claims to identify chronic disease outcomes. The findings are an excellent addition to the evidence supporting the contention that cardiorespiratory fitness helps people thrive.

Research on healthy aging is important for its insights into living longer, healthier, and more active lives and, potentially, reducing health care costs. In addition to observational studies such as the present one, clinical trials are needed to establish definitively the benefits and risks of approaches that have been shown in observational studies to be associated with extending health and life.8 One study that should provide evidence on whether exercise in the elderly contributes to healthy aging is the Lifestyle Interventions and Independence for Elders (LIFE) trial supported by the National Institute on Aging and the National Heart, Lung, and Blood Institute (clinicaltrials.gov Identifier: NCT01072500). The LIFE Study is a phase 3 multicenter, randomized controlled trial that compares a moderate-intensity physical activity program with a successful aging health education program in 1600 sedentary older persons who will be monitored for an average of 2.7 years. The primary outcome is major mobility disability; however, many secondary chronic disease outcomes relevant to healthy aging will be examined.

Physical activity has a host of well-proven benefits, including effects on weight, cardiovascular disease risk factors, bone health, and mental health. Resultant physical fitness may also help individuals maintain health and delay death and get our societal survival curves into the best shape: rectangular.

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Article Information

Correspondence: Dr Bild, Division of Cardiovascular Sciences, National Heart, Lung, and Blood Institute, 6701 Rockledge Dr, Mail Stop Code 7938, Bethesda, MD 20892 (bildd@nhlbi.nih.gov).

Published Online: August 27, 2012. doi:10.1001/archinternmed.2012.3406

Financial Disclosure: None reported.

Disclaimer: The views expressed herein are those of the author and do not necessarily reflect the official views of the National Heart, Lung, and Blood Institute.

References
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