Total physical activity and mortality were inversely related in men
ACP J Club. 1995 Sept-Oct;123:53. doi:10.7326/ACPJC-1995-123-2-053
Lee IM, Hsieh CC, Paffenbarger RS Jr. Exercise intensity and longevity in men. The Harvard Alumni Health Study. JAMA. 1995 Apr 19;273:1179-84.
To determine whether an association exists between vigorous and nonvigorous physical activity and longevity in men.
Cohort study of participants in the Harvard Alumni Health Study with 22-year follow-up.
Harvard University, Boston, Massachusetts, USA.
17 321 men (mean age 46 y) who were Harvard University alumni and free of self-reported, physician-diagnosed cardiovascular disease, cancer, or chronic obstructive pulmonary disease at the baseline questionnaire in 1962 or 1966.
Assessment of risk ractors
At baseline, data were collected by questionnaire on physical activity, body weight, height, cigarette habit, physician diagnosis of hypertension and diabetes mellitus, vital status of both parents, and, if parents were deceased, age of parental death. Each physical activity was assigned a multiple of resting metabolic rate (MET score). Physical activities were categorized as vigorous (requiring ≥ 6 METs) and nonvigorous (requiring < 6 METs).
Main outcome measure
3728 deaths occurred during follow-up. Mortality generally declined with increasing total energy expenditure (P = 0.001). Total energy expenditure and energy expenditure from vigorous activities were inversely related to mortality. This was not the case with energy expenditure from nonvigorous activities. After adjustment for potential confounders (age, body mass index, smoking, hypertension, diabetes, and early parental death [< age 65 y]), total energy expenditure, in quintiles, continued to relate inversely with mortality. The adjusted relative risks (RRs) were 1.00 (referent), 0.94 (95% CI 0.86 to 1.04), 0.95 (CI 0.86 to 1.05), 0.91 (CI 0.83 to 1.01), and 0.91 (CI 0.82 to 1.00), respectively (P < 0.05 for trend). The RRs for dying associated with < 630, 630 to < 1680, 1680 to < 3150, 3150 to < 6300, and ≥ 6300 kJ/wk expended on vigorous activities were 1.00 (referent), 0.88 (CI 0.82 to 0.96), 0.92 (CI 0.82 to 1.02), 0.87 (CI 0.77 to 0.96), and 0.87 (CI 0.78 to 0.97), respectively (P = 0.007). The corresponding RRs for energy expended on nonvigorous activities were 1.00 (referent), 0.89 (CI 0.79 to 1.01), 1.00 (CI 0.89 to 1.12), 0.98 (CI 0.88 to 1.12), and 0.92 (CI 0.82 to 1.02) (P = 0.36).
Total physical activity and mortality were inversely related in men. Vigorous but not nonvigorous activities were associated with longevity.
Source of funding: National Institutes of Health.
For article reprint: Dr. I.M. Lee, Department of Epidemiology, Harvard School of Public Health, 677 Huntington Avenue, Boston, MA 02115, USA. FAX 617-734-1437
Does physical activity reduce the risk for CVD and all-cause mortality? The articles by Blair and colleagues and Lee and colleagues approach this important question from different perspectives. Blair and colleagues have evaluated whether a change in physical fitness would alter CVD and all-cause mortality in men who presented for 2 preventive health examinations separated by a mean of 4.9 years. More than 30% of their participants had chronic health conditions. The fitness marker was endurance time on 2 age-adjusted treadmill tests (e.g., > 14 min for men aged 20 to 39 y) done 5 years apart. Outcome was examined by referring to the National Death Index in the 5 years after the second examination. Blair and colleagues found that men who were fit at both evaluations or, better still, who increased their fitness level from the first to the second test had appreciably reduced CVD and all-cause mortality.
Lee and colleagues looked at the association between all-cause mortality and increased daily energy expenditure (self-reported) by doing vigorous (≥ 6 METs) or nonvigorous (< 6 METs) physical activity. A MET is the oxygen uptake at rest (in a normal person, about 250 mL/min). A 6-fold increase in the metabolic rate would correspond to walking at a brisk rate (> 4 mph). The participants were Harvard alumni men enrolled from 1916 to 1950 who returned a questionnaire. Attempts were made to exclude men with chronic medical conditions. Lee and colleagues found that increased levels of total energy expenditure and energy expenditure from vigorous (but not nonvigorous) activities were associated with reductions in all-cause mortality.
Physical activity (of which regular aerobic exercise is a subset) results in physical fitness (1). One way to measure fitness and to identify a training response from physical activity is to quantify maximal oxygen uptake during exercise. Aerobic fitness was quantified by Blair and colleagues using the proxy variable of exercise treadmill time, but the amount and type of exercise done to achieve that fitness level were not reported. In contrast, Lee and colleagues recorded historically the amount, type, and frequency of exercise, but not the result of this activity (i.e., the aerobic fitness level). It is tempting to combine the results of these studies and conclude that the mechanism by which a vigorous exercise program improves mortality is linked to improvements in aerobic fitness, but this conclusion is not possible because of the observational nature of these data.
A further limitation of both studies is the lack of women. Also, little ethnic diversity was present and the participants were probably well educated, highly motivated, and of high socioeconomic status. The findings may not apply to persons with fewer advantages.
Finally, the exercise level (vigorous vs nonvigorous) necessary to achieve a reduction in all-cause (or CVD) mortality may be different than the exercise levels required to control hypertension, improve glucose tolerance, augment immune function in cancer or human immunodeficiency virus infection, decrease anxiety and depression, and control obesity. In most cases, the precise mechanisms by which exercise exerts its various beneficial effects are unknown. We need to give this "therapy" in the correct amount to avoid injury to participants, loss of lifelong motivation to exercise, and a possible decline in mortality benefit with extremely high levels of energy expenditure (as suggested by the data of Lee and colleagues). The current recommendations by the Centers for Disease Control and Prevention and the American College of Sports Medicine (1) are that every adult in the United States accumulate ≥ 30 minutes of moderately intense physical activity on most, preferably all, days of the week. These 2 excellent studies and several recent studies (2-4) suggest that it is important for practicing physicians to start emphasizing the benefits of exercise in preventive medicine. The most important prescription you give during your next office encounter may be the exercise prescription.
William W. Stringer, MD
Harbor-University of California at Los Angeles Medical CenterTorrance, California, USA
1. Pate RR, Pratt M, Blair SN, et al. Physical activity and public health. A recommendation from the Centers for Disease Control and Prevention and the American College of Sports Medicine. JAMA. 1995;273:402-7.