The power of prevention and what it requires.

BENJAMIN FRANKLIN’S ADAGE THAT AN OUNCE OF PREvention is worth a pound of cure is worth remembering at this worrisome time for health care and the economy. The prevalence of chronic illnesses in the United States is projected to increase, from 133 million persons in 2005 to 171 million in 2030. Health care spending accounts for 16% of the gross domestic product and may reach 25% by 2025. Rising health care costs are eroding corporate profits and threaten Medicare solvency, state budgets, pensions, and the viability of employersponsored health insurance. Family medical bills, insurance premiums, and the number of uninsured persons are increasing. Policy makers have proposed solutions (eg, valuebased purchasing, consumer-directed plans, information technology), but whether these are enough to alter the spending trajectory or can overcome the political challenges remains unclear. A more direct strategy for confronting both spending and disease burden is to mitigate the problem at its source by preventing the early onset of disease. Health promotion and disease prevention—eg, behavior modification, immunizations, and early detection (screening)—can modulate the prevalence and severity of disease, something few other proposals can claim. Prevention also may be an easier concept for the public—the politics are less volatile, the logic more intuitive: it is better to prevent diseases than to concentrate resources on treating diseases after they become clinically apparent, when treatment may be too late to be effective. Even though disease prevention has its limitations, its potential benefits are profound. Chronic diseases, which account for 75% of health care expenditures, are precipitated by modifiable risk factors. The relationship between the obesity epidemic and diabetes incidence is illustrative. Targeting risk factors such as obesity can influence disease rates and costs on a scale that few biomedical advances can match. A new diabetes drug can make headlines if it reduces glycohemoglobin levels by 0.5%, whereas exercise can lower the incidence of diabetes by 50%. Four health behaviors (smoking, diet, physical inactivity, and alcohol use) account for 38% of all US deaths. Other forms of primary prevention can intervene more dramatically, as when vaccines all but eradicate infectious diseases. Secondary prevention (screening) can reduce colorectal and breast cancer mortality by 15% to 20%. The business case for prevention is not lost on employers and policy makers. Fortune 500 companies have calculated that tobacco use costs $157 billion per year in medical expenses and lost productivity. Economists have predicted that the obesity epidemic could increase future Medicare beneficiary spending by 34%. The glaring paradox is how little society invests in prevention, only 1% to 3% of health care expenditures. Instead, health plans spend heavily on illness care, covering costly technologies even without evidence of benefit, while proceeding cautiously to cover preventive services. Funding for prevention research and public health programs is scarce. This paradox is long-standing, but it grows more unsettling with time as the human toll of preventable disease increases. Resistance to health promotion and disease prevention has multiple causes, including skepticism about effectiveness, inertia, and competing interests. Disease prevention does not earn the large profits associated with disease treatments. That inertia and such disincentives dampen enthusiasm for health promotion and disease prevention is straightforward, but skepticism about effectiveness is more complex. Some skepticism reflects disappointments with health promotion and disease prevention. Health behaviors are notoriously difficult to change. Decades of public health initiatives to promote a healthy diet and physical activity have failed to reverse the obesity epidemic. Years must pass before many interventions bear fruit. Hundreds of screening tests are of dubious value, and many are overzealously promoted. However, a cadre of important preventive services is supported by compelling evidence of health benefits and cost-effectiveness. The magnitude and quality of the outcomes data for these services surpass those of most disease treatments, yet the latter somehow elude the skepticism associated with preventive measures. Some criticism turns on flawed premises. For example, skeptics of prevention argue that everyone dies of some-