Public Health Focus: Physical Activity and the Prevention of Coronary Heart Disease

Coronary heart disease (CHD) is the leading cause of mortality in the United States: each year, CHD is newly diagnosed in approximately 1.5 million persons and accounts for an estimated $47 billion in direct and indirect health-care costs (1). Multiple risk factors associated with CHD include genetic susceptibility, elevated serum cholesterol, low levels of high-density lipoprotein cholesterol, cigarette smoking, uncontrolled hypertension, obesity, diabetes mellitus, and physical inactivity (2). This report summarizes information about the potential efficacy and cost-effectiveness of physical activity promotion as a strategy for preventing CHD. Efficacy and Attributable Risk

Mild to moderate levels of physical activity (e.g., walking, gardening, yardwork, and dancing) can help prevent CHD. In 1987, a review of 43 epidemiologic studies concluded that moderate to vigorous physical activity reduces risk for CHD (3). Two thirds of the studies documented a substantial inverse relation between physical activity and risk for CHD. In addition, the risk for CHD was increased nearly twofold for persons who were physically inactive (relative risk=1.9; 95% confidence interval=1.4-2.5), a level comparable to the relative risks associated with increased systolic blood pressure (2.1), cigarette smoking (2.5), and elevated serum cholesterol (2.4) (4). A subsequent meta-analysis (5) and results from other longitudinal studies (6) support the role of physical inactivity as a strong and independent risk factor for CHD.

Based on a national survey in 1985, 56% of men and 61% of women in the United States either never or irregularly engaged in physical activity (7). Specifically, 25% of men and 30% of women reported no leisure-time physical activity during the preceding month, and an additional 31% of men and women reported irregular physical activity. Of the 36% of men and 32% of women who were regularly active during leisure time, 8% of the men and 7% of the women reported participating in vigorous and intense activity (7).

An estimate of the population-attributable risk for CHD mortality associated with physical inactivity among a selected group of men from 1977 through 1985 was 14% (6). In comparison, the risk for hypertension was 20%; for cigarette smoking, 13%; and for a positive family history of premature parental death, 20%. An analysis based on published studies and the U.S. death rate to estimate the number of deaths attributed to several risk factors for nine chronic diseases (8) indicated that, in 1986, a total of 205,254 deaths associated with CHD were attributed to never or irregularly engaging in physical activity -- a number in excess of estimates for smoking (148,879), obesity (190,456), and hypertension (171,121) but similar to the estimates for elevated serum cholesterol (253,194). Cost-Effectiveness

Based on 1989 mortality estimates for CHD, the extrapolated cost of physical inactivity is $5.7 billion; among other risk factors for CHD, only elevated serum cholesterol (greater than or equal to 200 ug/dL) has a higher estimated cost (Table_1). A cost-effectiveness analysis to estimate the health and economic implications of a physical activity program in preventing CHD was conducted using a model of two hypothetical cohorts (one physically active and another inactive) of 1000 men aged 35 years (9). This analysis was based on a 30-year period to observe differences in the occurrence of CHD events, life expectancy, and quality-adjusted life expectancy. Physical activity was associated with 78 fewer CHD events and 1138 quality-adjusted life-years gained during the 30-year period. For each quality-adjusted life-year gained, the direct cost was $1395, and total cost was $11,313 -- amounts similar to the cost savings of other CHD intervention strategies (Table_2).

In Canada, a program promoting physical activity in a selected worksite was evaluated after 12 years of operation (12). The program consisted of professionally led physical activity classes 2-3 times per week for 30-45 minutes per session; an onsite gymnasium and exercise equipment also were made available to employees of the company. Per capita medical claims were lower in the intervention site than in a control site having no promotion of physical activity (12). For each worker, the intervention program saved $679 in medical claims per year, a return of $6.85 on each dollar invested.

Other examples of worksite-based programs have been estimated to cost employers approximately $100-$400 per employee per year (13). The estimated rate of return is $513 per employee year, which includes reduced health-care costs and reduced loss of productivity. Reported by: Div of Chronic Disease Control and Community Intervention, National Center for Chronic Disease Prevention and Health Promotion; Applications Br, Div of Surveillance and Epidemiology, and Prevention Effectiveness Activity, Epidemiology Program Office, CDC.

Editorial Note

Editorial Note: Epidemiologic, clinical, and experimental evidence have established the association between physical activity and the prevention of CHD (3). The finding that moderate levels of physical activity reduce the risk for CHD indicates that inactive persons can benefit from even modest increases in their physical activity. Theoretical estimates suggest that, in the United States, 20,000 fewer persons would die per year if half of those persons with no leisure-time physical activity begin to participate in moderate physical activity (e.g., brisk walking) a minimum of 2-3 times per week (14 ). Biologic mechanisms through which physical activity may prevent CHD include improved weight control, enhanced glucose tolerance and insulin sensitivity, reduced blood pressure, improved coronary artery blood flow, and augmented high-density lipoprotein levels.

Educating health professionals and lay persons to implement effective ways to reduce risk factors for CHD and subsequent disease could result in a substantial savings in health-care costs. To increase and promote levels of physical activity, health-care and public health providers should consider those factors associated with inactivity. In particular, prevalence of inactivity is higher among older persons and women. In addition, inactivity has been associated with cognitive factors (e.g., knowledge of the benefits of activity, the perception of poor health, lack of time, and dislike for activity), personal attributes (e.g., obesity, low educational attainment, lack of self-motivation, and lack of confidence in ability to perform an activity), and environmental factors (e.g., lack of social support, inconvenience of activities, aversion to vigorous activities, and cost of activities) (15).

In addition to worksite-based programs, physical activity levels have been successfully increased in school-based programs for students, faculty, and staff and in the community (16). Community-based campaigns focusing on participation, awareness through media and education, and environmental efforts (e.g., increased access to trails, parks, and school facilities) have resulted in short-term improvements in the physical activity habits of targeted groups. Other potential sites for promoting physical activity include physician's offices and health clinics, as well as the home and neighborhood environment, where the emphasis should be on participation in a variety of self-directed, moderate-level physical activities (e.g., gardening, yardwork, and walking) with a goal of 30 minutes of activity per day at least 5 days per week.

References

1. American Heart Association. 1992 Heart and stroke facts. Dallas: American Heart Association, 1991.

2. Multiple Risk Factor Intervention Trial Research Group. Multiple Risk Factor Intervention Trial: risk factor changes and mortality results. JAMA 1982;248:1465-77.

3. Powell KE, Thompson PD, Caspersen CJ, Kendrick JS. Physical activity and the incidence of coronary heart disease. Annu Rev Public Health 1987;8:253-87.

4. Pooling Project Research Group. Relationship of blood pressure, serum cholesterol, smoking habit, relative weight and ECG abnormalities to incidence of major coronary events: final report of the Pooling Project. J Chronic Dis 1978;31:202-306.

5. Berlin JA, Colditz GA. A meta-analysis of physical activity in the prevention of coronary heart disease. Am J Epidemiol 1990;132:639-46.

6. 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;328:538-45.

7. Caspersen CJ, Christenson GM, Pollard RA. Status of the 1990 physical fitness and exercise objectives -- evidence from NHIS 1985. Public Health Rep 1986;101:587-92.

8. Hahn RA, Teutsch SM, Rothenberg RB, Marks JS. Excess deaths from nine chronic diseases in the United States, 1986. JAMA 1990;264:2654-9.

9. Hatziandreu EI, Koplan JP, Weinstein MC, Caspersen CJ, Warner KE. A cost-effectiveness analysis of exercise as a health promotion activity. Am J Public Health 1988;78:1417-21.

10. Weinstein MC, Stason WB. Cost-effectiveness of intervention to prevent or treat coronary heart disease. Annu Rev Public Health 1985;6:41-63.

11. Oster G, Colditz GA, Kelly NL. The economic costs of smoking and benefits of quitting for individual smokers. Prev Med 1984;13:377-89.

12. Shephard RJ. Twelve years experience of a fitness program for the salaried employees of a Toronto life assurance company. American Journal of Health Promotion 1992;6:292-301.

13. Shephard RJ. Current perspectives on the economics of fitness and sport with particular reference to worksite programmes. Sports Med 1989;7:286-309.

14. Powell KE, Blair SN. The public health burdens of sedentary living habits: theoretical but realistic estimates. Med Sci Sports Exerc (in press).

15. King AC, Blair SN, Bild DE, et al. Determinants of physical activity and interventions in adults. Med Sci Sports Exerc 1992;24(suppl):221S-36S.

16. Iverson DC, Fielding JE, Crow RS, Christenson GM. The promotion of physical activity in the United States population: the status of programs in medical, worksite, community, and school settings. Public Health Rep 1985;100:212-24.

Table_1
Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 1. Population attributable risk of coronary heart disease (CHD) deaths and
estimated societal costs, by selected risk factors -- United States *
================================================================================================
                              Attributable risk (%) +    Estimated cost
       Risk factor                 (n=593,111)            (billions) &
----------------------------------------------------------------------------------------------
       Physical inactivity            34.6                    $5.7
       Obesity                        32.1                    $5.3
       Smoking                        25.0                    $4.1
       Hypertension                   28.9                    $4.7
       Elevated serum
         cholesterol
         (>=200 ug/dL)                42.7                    $7.0
----------------------------------------------------------------------------------------------
* Source: Reference 8.
+ Percentages cannot be summed because they are calculated independently for each risk factor.
& Costs include hospital, physician, and nursing services; medicines; and lost productivity.
================================================================================================

TABLE 2. Selected risk factors for coronary heart disease, by prevalence, population-
attributable risk, and cost effectiveness -- United States
============================================================================================
   Risk factor          Prevalence (%)   Attributable risk (%) *    Cost effectiveness
------------------------------------------------------------------------------------------
   Physical inactivity      58.0                 34.6               $11,313 per QALY +
   Hypertension             18.0                 28.9               $25,000 per QALY &
   Smoking                  25.5                 25.0              $21,947 total lifetime
                                                                    benefits of quitting @
   Obesity                  23.0                 32.1                        NA**
   Elevated serum
     cholesterol
     (>=200 ug/dL)          37.0                 42.7              $28,000 per QALY ++
------------------------------------------------------------------------------------------
 * Percentages cannot be summed because they are calculated independently for each risk
   factor.
 + Quality-adjusted life-years.
 & Source: Reference 9.
 @ Source: Reference 10.
** Not available.
++ Source: Reference 11.
============================================================================================

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