Experts agree that exercise is highly beneficial to health. But what are the most cost-effective ways for public health officials and other policy makers on limited budgets to encourage people to exercise?
Shinyi Wu: Measuring how many more METs. Click on the image to hear a podcast
The 91 were chosen from a huge volume of candidate interventions, described in some 5,579 publications that Wu and her team analyzed, focusing on those that had characterized the resulting gain in exercise precisely enough to quantify it.
The measure of exercise is the MET-hour, or the amount of energy consumed in one hour by an individual who is idle. On this measure, each person consumes 24 MET-hours per day without exercise. For health, adults should consume at least 25.5 MET hours – that is, exercise enough so that they additionally use the equivalent of an extra 1.5 hours of idleness. This amounts to 30 minutes of moderate physical activity per day – walking briskly, for example. Children need double this figure, 3 MET hours.
The researchers used the study descriptions to calculate the gain in MET hours produced by each program, multiplying the number of participants motivated by the program by the average MET hour gain produced by each program per day. They then divided this figure by the program's cost, to create rankings in terms of exercise gain per dollar per person per day.
The most cost effective? Simple signs next to elevators suggesting people use the stairs added exercise at a cost of 7 cents per MET-hour/day per person. (The problem: the gain was tiny, only 2 percent of the needed extra 1.5 MET-hours.) High intensity coaching and social support programs produced much more activity, up to 43 percent of the recommended level – but the gain came at a much higher cost, often more than $1 per MET-hour/day per person. Some school programs for students were relatively cost-effective, at about 42 cents per MET-hour/day per child.
The 2011 paper, "Economic Analysis of Physical Activity Interventions," published in the American Journal of Preventive Medicine contains a comparison of 17 programs that illustrates a range of interventions and effectiveness.
The paper noted a necessity for better, more quantitative work by policy makers. “Future interventions to promote physical activity should take care to report resources utilized and costs.… Given the large task of increasing physical activity among a sedentary population, a wide variety of options are needed to enhance the likelihood of adoption among disparate target populations."
Professor Wu is with the USC Viterbi’s Daniel J. Epstein Department of Industrial and Systems Engineering. She began the study while working at the RAND Corporation, and completed it at USC. Her co-authors, all at RAND, include Deborah Cohen, Yuyan Shi, Marjorie Pearson, and Roland Sturm. The National Cancer Institute funded the study, (Am J Prev Med 2011;40(2):149 –158)