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E-1 APPENDIX E USER HEALTH BENEFITS The benefits of physical activity in enhancing overall health are well established. Physical activity reduces the risk of chronic diseases including coronary heart disease (170, 205â209), hypertension (210), Type II (non-insulin dependent) diabetes mellitus (211, 212), osteo- porosis (213, 214), cancer (215â217) and mental illness (95, 218â220). Inversely, reduced levels of physical activity are also associated with mortality rates in general (221â223). The task of attaching monetary amounts to levels of physical activity is a more challenging endeavor. One attempt to this gen- eral inquiry has been completed by Wang et al. (93) who derived cost-effectiveness measures of bicycle/pedestrian trails by divid- ing the costs of trail development and maintenance by selected physical activity-related outcomes of the trails (e.g., number of trail users). The average annual cost for persons becoming more physically active was found to be $98; the cost was $142 for per- sons who are active for general health, and $884 for persons who are active for weight loss. Estimating the effect of physical activity on direct medical costs is a strategy more often employed, though considerably less straightforward. Part of the reason for ambiguity in this line of research is that an unsettled question looms as to how much phys- ical activity is required to realize certain health benefits (i.e., what is the elasticity?) (88, 94, 95). In the field of public health, this matter is often approached from the perspective of dose-response relationships. The aim is to learn what change in amount, inten- sity, or duration of exposure (in this case, cycling) is associated with a change in risk of a specified outcome (in this case, cost of health care). Existing literature examining relationships between levels of physical activity and health costs varies considerably in methodol- ogy and scope. The majority of existing studies pursue a dichot- omized approach, separating respondents into two classes: those that satisfy the accepted âdoseâ of 30 minutes per day for five days and those who do not. In this first group of studies, there are at least five statewide reports whose methodology and assumptions are rel- atively general in nature. In most cases, estimates are derived from an aggregation of medical expenditures that can in some form be traced back to physical inactivity. For example, a study commis- sioned by the Michigan Fitness Foundation (96) concentrated on the economic costs to the residents of Michigan. The authors used estimates (acknowledged to be conservative) to derive direct costs (e.g., medical care, workersâ compensation, lost productivity) and indirect costs (e.g., inefficiencies associated with replacement workers). The final amount totaled $8.9 billion in 2003 ($1,175 per resident). A 2002 report from the Minnesota Department of Health (97) estimates that in 2000, $495 million was spent treating dis- eases and conditions that would be avoided if all Minnesotans were physically active. This amount converts to over $100 per resident. Additional reports claim that too little physical activity was responsible for an estimated $84.5 million ($19 per capita) in hospi- tal charges in Washington State (98), $104 million ($78 per capita) in South Carolina (99), and $477 million in hospital charges in Georgia ($79 per capita) (100). These reports from various state agencies are complemented with more academically oriented research. For example, Colditz (101) reviewed past literature on the economic costs of inactivity and concluded that the direct costs for those individuals reporting lack of physical activity was estimated to average approximately $128 per person. A separate analysis by Pratt et al. (102) analyzed a stratified sample of 35,000 Americans from the 1987 national Medical Expenditures Survey. Examining the direct medical costs of men and women who reported physical activity versus those who did not reveals that the mean net annual benefit of physical activ- ity was $330 per person in 1987 dollars. An alternative method used a cost-of-illness approach to attribute a proportion of medical and pharmacy costs for specific diseases to physical inactivity in 2001 (97). The authors first identified medical conditions associ- ated with physical inactivity and then collected claims data related to those conditions from approximately 1.6 million patients 16 and older from a large, Midwest health plan. While the resulting con- ditions from lack of physical inactivity include depression, colon cancer, heart disease, osteoporosis, and stroke, the results from this study conclude that claims costs at the health plan attributable to physical inactivity translates to $57 per member. One challenge of these analyses is the decision regarding whether or not to include diseases causally related to obesity or not. The Garrett paper did not, which may account for the lower estimates of cost of inactiv- ity per person. A different approach than the dichotomized strategy estimates the impact of different modifiable health risk behaviors and mea- sures their impact on health care expenditures. After gathering information from more than 61,500 employees of six employers gathered over a five-year study period, Goetzel et al. (87) focused on a cohort of just over 46,000 employees, one-third of whom were considered to be sedentary (or inactive). The analysis found that a ârisk-freeâ individual incurred approximately $1,166 in average annual medical expenditures while those with poor health habits had average annual medical expenditures of more than $3,800. Thus, they estimated the per-capita annual impact of poor exercise habits to be approximately $172. Pronk et al. (89) also identify the relationship between modifiable health risks and short- term health care charges. This research surveyed a random sample of 5,689 adults aged 40 years or older enrolled in a Minnesota health plan. Multivariate analysis on the modifiable health risks (diabetes, heart disease, body mass index, physical activity and smoking status) concluded that an additional day of physical activ- ity (above zero) would yield a 4.7 percent reduction in charges (or a $27.99 reduction). The overarching result of the study is that obesity costs approximately $135 per member per year, and those with low fitness (inactivity) cost approximately $176 per member per year. From this discussion, a couple of matters stand out with respect to understanding such relationships and ultimately informing applica- ble methods. First, annual per capita cost savings vary between $19 and $1,175 with a median value of $128 (see Table 25). Second,
E-2 some studies are disaggregate in nature and estimate costs by in- patient, outpatient, and pharmacy claims; others compare average healthcare expenditures of physically active versus inactive indi- viduals. Third, some use a dichotomized approach to operational- ize physically active individuals while others employ a modifiable health risks approach and do so in a relatively continuous scale. The studies are difficult to compare because some include different conditions, outpatient and pharmacy costs, and actual paid amounts rather than charges. Nonetheless, existing literature provides ade- quate, though developing, methodologies for estimating the public health impact of bicycle facilities in terms of economic impacts. Study/Agency Per Capita Cost Savings ($) Washington State Department of Health 19 Garrett et al. 57 South Carolina Department of Health 78 Georgia Department of Human Resources 79 Colditz (1999) 92 Minnesota Department of Health >100 Goetz et al. 172 Pronk et al. 176 Pratt 330 Michigan Fitness Foundation 1,175 TABLE 25 Estimated annual per capita cost savings (direct and/or indirect) of physical activity (103)
