Preventive Care and Health Screening: What Research Shows About What Works

Preventive care is commonly described as an investment that saves money and lives by catching diseases early or preventing them from occurring. This claim has intuitive appeal but deserves examination against the evidence, which shows that some preventive services produce clear benefits while others are less effective than promoted and some carry harms that proponents often understate. Understanding what research shows about the effectiveness and cost-effectiveness of preventive care allows patients and clinicians to make informed decisions about which services are genuinely worth pursuing. The United States Preventive Services Task Force is an independent panel of experts in preventive medicine and primary care that reviews evidence and makes recommendations about preventive services for asymptomatic adults and children. Task Force recommendations, which range from A and B grades for services with clear net benefit to D grades for services with a negative net benefit, are based on systematic reviews of clinical trial and observational evidence. These recommendations carry regulatory weight because the Affordable Care Act requires most insurance plans to cover A and B recommended services without cost-sharing. Cancer screening represents one of the most significant areas of preventive care and one of the most complex from an evidence standpoint. Colorectal cancer screening has strong evidence of effectiveness, with multiple modalities including colonoscopy, stool-based tests, and flexible sigmoidoscopy all showing reductions in colorectal cancer incidence and mortality. Breast cancer screening with mammography reduces breast cancer mortality for women in their 50s, though the magnitude of benefit and the appropriate starting age and frequency are subjects of ongoing evidence review and some controversy given the rate of false positives and overdiagnosis. Cervical cancer screening with Pap smears and HPV testing has dramatically reduced cervical cancer mortality and is among the most clearly successful cancer screening programs. Lung cancer screening with low-dose CT scanning for heavy smokers and former smokers is a relatively recent addition to recommended preventive services, based on the National Lung Screening Trial finding a 20 percent reduction in lung cancer mortality compared to chest X-ray in high-risk individuals. However, uptake has been low, partly because the high-risk population that qualifies is difficult to identify and engage in primary care settings, and partly because the logistics of implementing screening with the appropriate follow-up and shared decision-making are complex. The concept of overdiagnosis, which refers to the detection of cancers or other conditions through screening that would never have caused symptoms or death in the individual's lifetime, is now well-recognized in the preventive care literature. Prostate cancer screening with PSA testing is the clearest example: randomized trials find that PSA screening reduces prostate cancer mortality modestly but produces large amounts of overdiagnosis, with many men treated for cancers that would never have harmed them, exposing them to treatment side effects including urinary incontinence and sexual dysfunction with no corresponding benefit. The Task Force dropped its recommendation for routine PSA screening for this reason, though the recommendation remains controversial in urology. Cardiovascular disease prevention is another major area where research on preventive interventions is well-developed. Statin medications for primary prevention, meaning in people without existing cardiovascular disease, reduce cardiovascular events in individuals with elevated risk profiles. Aspirin, which was widely recommended for primary prevention of cardiovascular disease for decades, has been reconsidered by the Task Force following evidence that the bleeding risks in older adults and in people without a prior cardiovascular event outweigh the benefits in those populations. This revision illustrates how evidence evolves and how practice recommendations should follow. The claim that preventive care saves money overall is not consistently supported by research. Some preventive services are cost-effective, meaning they produce health benefits at reasonable cost relative to alternatives, without being cost-saving. A service is cost-effective if the health gains it produces are worth the money spent, not if it produces net savings. Some highly targeted preventive interventions do save money, particularly those that prevent expensive hospitalizations in high-risk populations. But broad screening programs applied to low-risk populations often cost more than they save, and this reality should inform policy discussions about preventive care as a budget strategy. Preventive care access is unequal, with lower-income populations and those without insurance or with high cost-sharing requirements less likely to receive recommended services. The elimination of cost-sharing requirements for preventive services under the Affordable Care Act was intended to address this barrier, and research finds that it increased uptake of some preventive services. However, access barriers beyond cost, including time off work for appointments, transportation, and limited provider availability, continue to produce disparities in preventive care receipt. Shared decision-making, the process by which clinicians and patients discuss the potential benefits, harms, and individual values relevant to screening decisions, is increasingly emphasized in preventive care guidelines. Research on decision aids for cancer screening finds that they improve knowledge, reduce decisional conflict, and produce choices that are more consistent with patient values than decisions made without decision support. Implementing shared decision-making at scale in primary care, where time is short and competing demands are many, remains a challenge that healthcare systems are working to address.