Commentary: Can walking lower medical care costs?

Caroline A Macera

San Diego State University, San Diego, CA 92182–4162, USA. E-mail: cmacera{at}mail.sdsu.edu

There is a great deal of evidence that supports the health benefits of physical activity for the general population. For instance, participating in at least 30 minutes of moderate intensity physical activity (such as brisk walking) has been shown to reduce morbidity and mortality due to chronic disease and disability.1 Walking is the most accessible form of physical activity and is recommended for health benefits because it is an activity most people can do and is associated with a very low injury rate. While it makes sense to recommend walking for health benefits and it is logical to assume that promoting physical activities such as walking could translate into lower medical care expenditures, it has been difficult to find quantitative data to make the case that medical care costs are lower among individuals who walk than those who do not. There are few studies that can directly address the medical costs of physically active adults. The study reported in this issue of the International Journal of Epidemiology by Tsuji et al.2 is one of the first large studies to look at walking by linking direct medical care costs and health behaviour databases.

The authors found that those who walked more than one hour per day had lower medical care costs and lower inpatient and outpatient utilization rates compared with those who spent less time walking. It is interesting to note that at first the accumulated medical costs per person were similar, but after 18 months differences appeared between the walking groups and these differences continued to increase throughout the observation period. This time lag makes sense because one would expect the association of physical activity and illness in healthy people to occur after some time has passed. In this study, they specifically eliminated those who may already be sick and unable to participate in physical activities such as walking. This finding illustrates why it is difficult to look at medical costs associated with physical activity in short-term studies.

Among the many advantages of this study are the large sample size, the ability to link walking behaviour data with standardized fee medical utilization data, and the ability to control for confounders. However, it is not known how representative this mostly rural population is of the general population in Japan, which would include urban areas. Furthermore, the National Health Insurance (NHI) system covers farmers, self-employed, and pensioners, which may not represent others, and only covered about 55% of those in this rural study area.

After exclusions, the final study population included only healthy individuals who were able to be physically active. However, these healthy individuals that formed the study group represented only about half of the 52 029 who responded to the questionnaire and were part of the original cohort. Of the eligible cohort, almost one-third (15 858) were eliminated because they could not participate in moderate or vigorous physical activity. In addition, those with some chronic conditions, including arthritis were also eliminated from the study. These exclusions resulted in conservative estimates of medical care costs. Although in general, people with arthritis are not as active as those without arthritis, another study found lower medical costs among active people with arthritis when compared with inactive people with arthritis.3 Further analyses of the NHI data might show that physical activities such as walking may result in medical care cost savings even among those with chronic conditions.

As the authors correctly point out, high levels of walking may be related to high levels of other kinds of activity so the findings may not be due to walking alone. The group who walked more than one hour a day also had a higher percentage reporting spending >=3 hours per week on sports and exercise. While more work needs to be done to ascertain the type, intensity, and amount of physical activity that is most associated with reduced medical costs over time, it is encouraging to see these differences apparent even with an inexact marker such as time spent walking.

With the large sample size (15 019 men and 12 412 women) it would have been good to see gender-specific costs, although the authors state that there were no gender differences. There are many differences in medical care utilization among men and women, and exploring cost differences by gender may have yielded interesting results, especially for the accumulated medical costs over time as shown in Figure 1.

Studies such as this are very important in understanding the role of a healthy and active lifestyle in promoting long-term functional health. As documentation becomes available showing lower medical care costs among active individuals, more resources may be made available for long-term population-based programmes and environmental changes to promote physical activity, especially walking, as people age.


    References
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 References
 
1 United States Department of Health and Human Services. Physical Activity and Health: A Report of the Surgeon General. Atlanta: Centers for Disease Control and Prevention, 1996.

2 Tsuji I, Takahashi K, Nishino Y et al. Impact of walking on medical care expenditure in Japan: the Ohsaki Cohort Study. Int J Epidemiol 2003;32:809–14.[Abstract/Free Full Text]

3 Wang G, Helmick C, Macera CA, Zhang P, Pratt M. Inactivity-associated medical costs among US adults with arthritis. Arthritis Care and Research 2001;45:439–45.[Medline]





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