Correspondence

Walking and Mortality in Older Men

N Engl J Med 1998; 338:1622-1623May 28, 1998

Article

To the Editor:

Hakim et al. (Jan. 8 issue)1 reported an association between regular walking and lower overall long-term mortality in retired nonsmoking men. The observed reduction in mortality was significant for cancer deaths but not for cardiovascular deaths. The lack of benefit in reducing cardiovascular mortality conflicts with previous studies from the Honolulu Heart Program, which reported that physical activity is associated with lower mortality from coronary heart disease, even after adjustment for smoking status,2 and with a lower incidence of stroke in nonsmoking men.3 Furthermore, the association between walking and a lower risk of death from cancer is difficult to explain. The authors performed a precise adjustment of the effect of walking on mortality for cardiovascular risk factors. Although they attempted to adjust mortality reduction for disability and physical impairment, there was not an adequate control of confounding factors related to cancer or other causes. The relation between walking and lower mortality rates may not be causal. For instance, former smokers — apparently not excluded from the study — may have an impaired ability to walk due to chronic obstructive pulmonary disease, a condition associated with cancer4 and with an increased mortality risk.5 The hypothesis that walking a greater distance per day is a marker of less coexisting illness and lower cancer risk instead of a protector against overall and cancer-related mortality may have been too easily dismissed.

Héctor Bueno, M.D., Ph.D.
Maite Vidán, M.D., Ph.D.
Hospital General Universitario Gregorio Marañón, 28007 Madrid, Spain

5 References

1. 1

   Hakim AA, Petrovitch H, Burchfiel CM, et al. Effects of walking on mortality among nonsmoking retired men. N Engl J Med 1998;338:94-99
   Full Text | Web of Science | Medline

2. 2

   Rodriguez BL, Curb JD, Burchfiel CM, et al. Physical activity and 23-year incidence of coronary heart disease morbidity and mortality among middle-aged men. Circulation 1994;89:2540-2544
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3. 3

   Abbott RD, Rodriguez BL, Burchfiel CM, Curb JD. Physical activity in older middle-aged men and reduced risk of stroke: the Honolulu Heart Program. Am J Epidemiol 1994;139:881-893
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4. 4

   Tockman MS, Anthonisen NR, Wright EC, Donithan MG. Airways obstruction and the risk for lung cancer. Ann Intern Med 1987;106:512-518
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   Beaty TH, Newill CA, Cohen BH, Tockman MS, Bryant SH, Spurgeon HA. Effects of pulmonary function on mortality. J Chronic Dis 1985;38:703-710
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To the Editor:

Hakim and colleagues addressed the important question of the optimal amount of physical activity necessary for protection against several health problems, in particular cardiovascular disease. In contrast to other studies,1,2 they did not find a significantly lower risk of mortality from cardiovascular disease (coronary heart disease or stroke) with increased energy output from low-intensity physical activity (i.e., walking).

The authors quantified physical activity according to a self-reported questionnaire, which raises the possibility of bias toward an overestimation of this behavior. Furthermore, recall of walking, which is a ubiquitous, low-intensity activity, may be less accurate than recall of more vigorous pursuits (e.g., jogging and tennis). Because of the possibility of measurement error, it has become common practice to validate physical-activity questionnaires used in cohort investigations; in the studies reporting a significant inverse association between cardiovascular disease and low-intensity activity,1,2 the data from the questionnaires demonstrated adequate validity and high reliability.3,4 Although Hakim et al. indicate that similar versions of their questionnaire have been used in other cohort studies, this fact does not negate the need to validate the questionnaire by (1) a comparison with a device capable of accurately quantifying low-level physical activity — e.g., an accelerometer (to ensure concurrent validity) — and (2) a test–retest administration separated by a period of weeks (to ensure reliability).

David Batty, M.Sc.
University of Bristol, Bristol BS8 2LU, United Kingdom

4 References

1. 1

   Paffenbarger RS Jr, Wing AL, Hyde RT. Physical activity as an index of heart attack risk in college alumni. Am J Epidemiol 1978;108:161-175
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2. 2

   Leon AS, Connett J, Jacobs DR Jr, Rauramaa R. Leisure-time physical activity levels and risk of coronary heart disease and death. JAMA 1987;258:2388-2395
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3. 3

   Washburn RA, Smith KW, Goldfield SR, McKinlay JB. Reliability and physiologic correlates of the Harvard Alumni Activity Survey in a general population. J Clin Epidemiol 1991;44:1319-1326
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   Richardson MT, Leon AS, Jacobs DR Jr, Ainsworth BE, Serfass R. Comprehensive evaluation of the Minnesota Leisure Time Physical Activity Questionnaire. J Clin Epidemiol 1994;47:271-281
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Author/Editor Response

The authors reply:

To the Editor: The pattern of association between distance walked and cardiovascular disease does not conflict with data reported elsewhere from the Honolulu Heart Program. In earlier reports, an overall physical-activity index was used, not a measure of the distance walked. Although the distance walked was inversely related to death from coronary heart disease and stroke, the lack of a significant association could be attributed to the use of a small sample and the lower incidence of coronary heart disease that often characterizes men of Japanese ancestry. Even with these limitations, however, the physical-activity index continued to be significantly protective against death from these outcomes.

For our adjusted analysis of cancer, we eliminated prevalent cases from follow-up, adjusted for important confounders,1,2 excluded cigarette smokers, and controlled for nutrition. Our finding is also not the first that suggests physical activity may be protective against cancer.1-4 In addition, in an attempt to adjust for the presence of subclinical disease, we excluded the subjects who died within one year of follow-up with little effect on the association between walking and mortality. Impairments due to chronic obstructive pulmonary disease may also have been mitigated in our report by the inclusion of only men who were physically capable, and in an additional analysis, by the exclusion of men who were unable to walk at least a half mile per day. Walking continued to have a significant effect in reducing the risk of death for both past smokers and those who had never smoked.

We believe that the reliability of the self-reported distance walked in the Honolulu Heart Program is high. Walking in Hawaii is unlikely to be disrupted by changing seasons, as compared with other activities that may be practiced with less regularity in more hostile climates, particularly by the elderly. More vigorous activities may also occur too infrequently in the elderly to permit an analysis of their effect on mortality. For example, in our sample of 707 men, only 29 jogged. The reported distances walked in Hawaii were also observed to increase with increases in the amount of time spent in other self-reported activities, such as the number of hours of “slight activities” (defined as “walking on the level”). The responses to the question about the distance walked correlated well with the responses to the same question when it was asked 10 years later. Our findings are also consistent with those observed in a more diverse sample of Harvard alumni,5 further supporting the hypothesis that walking may have real effects in reducing the risk of death.

Amy A. Hakim, M.S.
University of Minnesota Medical School, Minneapolis, MN 55455

Robert D. Abbott, Ph.D.
University of Virginia School of Medicine, Charlottesville, VA 22908

5 References

1. 1

   Lee IM, Paffenbarger RS Jr, Hsieh CC. Physical activity and risk of prostate cancer among college alumni. Am J Epidemiol 1992;135:169-179
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2. 2

   Albanes D, Blair A, Taylor PR. Physical activity and risk of cancer in the NHANES I population. Am J Public Health 1989;79:744-750
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3. 3

   Colditz GA, Cannuscio CC, Frazier AL. Physical activity and reduced risk of colon cancer: implications for prevention. Cancer Causes Control 1997;8:649-667
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4. 4

   Oliveria SA, Lee IM. Is exercise beneficial in the prevention of prostate cancer? Sports Med 1997;23:271-278
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5. 5

   Paffenbarger RS Jr, Hyde RT, Wing AL, Lee I-M, Jung DL, Kampert JB. The association of changes in physical-activity level and other lifestyle characteristics with mortality among men. N Engl J Med 1993;328:538-545
   Full Text | Web of Science | Medline

Citing Articles (1)

Citing Articles

1. 1

   DAVID R. BASSETT. (2000) Validity of four motion sensors in measuring moderate intensity physical activity. Medicine & Science in Sports & Exercise 32:Supplement, S471-S480
   CrossRef