The Relationship of Health Insurance and Mortality: Is Lack of Insurance Deadly?

Key Summary Points In several specific conditions, the uninsured have worse survival, and the lack of coverage is associated with lower use of recommended preventive services. The Oregon Health Insurance Experiment, the only available randomized controlled trial that has assessed the health effects of insurance, suggests that it may cause a clinically important decrease in mortality, but wide CIs preclude firm conclusions. The 2 National Health and Nutrition Examination Study analyses that include physicians' assessments of baseline health show substantial mortality improvements associated with coverage. A cohort study that used only self-reported baseline health measures for risk adjustment found a nonsignificant coverage effect. Most, but not all, analyses of data from the longitudinal Health and Retirement Study have found that coverage in the near-elderly slowed health decline and decreased mortality. Two difference-in-difference studies in the United States and 1 in Canada compared mortality trends in matched locations with and without coverage expansions. All 3 found large reductions in mortality associated with increased coverage. A mounting body of evidence indicates that lack of health insurance decreases survival, and it seems unlikely that definitive randomized controlled trials can be done. Hence, policy debate must rely on the best evidence from observational and quasi-experimental studies. At present, about 28 million Americans are uninsured. Repeal of the Patient Protection and Affordable Care Act (ACA) would probably increase this number, whereas enactment of proposed single-payer legislation (1) would reduce it. The public spotlight on how policy changes affect the number of uninsured reflects a widespread assumption that insurance improves health. A landmark 2002 Institute of Medicine (IOM) report on the effects of insurance coverage on the health status of nonelderly adults buttressed this assumption (2). The IOM committee responsible for the report found consistent evidence from 130 (mostly observational) studies that the uninsured have poorer health and shortened lives and that gaining coverage would decrease their all-cause mortality (2). The IOM committee also reviewed evidence on the effects of health insurance in specific circumstances and medical conditions. It concluded that uninsured patients, even when acutely ill or seriously injured, cannot always obtain needed care and that coverage improves the uptake of essential preventive services and chronic disease management. The report found that uninsured patients with cancer presented with more advanced disease and experienced worse outcomes, including mortality; that uninsured patients with diabetes, cardiovascular disease, end-stage renal disease, HIV infection, and mental illness (the 5 other conditions reviewed in depth) had worse outcomes than did insured patients; and that uninsured inpatients received less and worse-quality care and had higher mortality both during their hospital stays and after discharge. At the time of the IOM report, only 1 adequately controlled observational study had examined the effect of coverage on all-cause mortality. In this review, we summarize key evidence on this issue (Table 1), focusing on studies that have appeared since the IOM report and other previous reviews (36). Although not reviewed in detail here, more recent studies generally support the earlier reviews' conclusions that insurance coverage reduces mortality in several specific conditions (such as trauma [7] and breast cancer [8]), augments the use of recommended care (9), and improves several measures of health status (10, 11). Table 1. Summary of Studies on Relationship Between Insurance Coverage and All-Cause Mortality* Methods We searched PubMed and Google Scholar on 19 May 2017 for English-language articles by using the following terms: [(uninsured) or (health insurance) or (uninsurance) or (insurance)] and [(mortality) or (life expectancy) or (death rates)]. After identifying relevant articles, we searched their bibliographies and used Google Scholar's cited by feature to identify additional relevant articles. We limited our scope to articles reporting data on the United States, quasi-experimental studies of insurance expansions in other wealthy nations, and recent cross-national studies. We contacted the authors of 4 studies to clarify their published reports on mortality outcomes. We excluded most observational studies that compared uninsured persons with those insured by Medicaid, Medicare, or the Department of Veterans Affairs because preexisting disability or illness can make an individual eligible for these programs. Hence, relative to those who are uninsured, publicly insured Americans have, on average, worse baseline health, thereby confounding comparisons. Conversely, comparing uninsured persons with those with private insurance (which is often obtained through employment) may be confounded by a healthy worker effect: that is, that persons may lose coverage because they are ill and cannot maintain employment. Nonetheless, most analysts of the relationship between uninsurance and mortality have viewed privately insured persons as the best available comparator, with statistical controls for employment, income, health status, and other potential confounders. Finally, we focus primarily on nonelderly adults because most studies have been limited to this group, and this group is likely to experience large gains or losses of coverage from health reforms. Since the advent of Medicare in 1966, almost all elderly Americans have been covered, precluding studies of uninsured seniors. Although Medicare's implementation may not have accelerated the secular decline in seniors' mortality (12), the relevance of this experience, which predates many modern-day therapies, is unclear. Children have also been excluded from most recent analyses of the relationship of insurance to mortality. Death in this population beyond the neonatal period is so rare that studies would need to evaluate a huge number of uninsured children to reach firm conclusions, and high coverage rates make assembling such a cohort difficult. The few studies addressing the effect of insurance on child survival have found that coverage reduces mortality (1315), and few policy leaders contest the importance of covering children. Randomized Controlled Trials Only 1 well-conducted randomized controlled trial (RCT)the Oregon Health Insurance Experiment (OHIE)has assessed the effect of uninsurance on health outcomes (10, 16). In 2008, the state of Oregon opened a limited number of Medicaid slots to poor, able-bodied, uninsured adults aged 19 to 64 years. The state held a lottery among persons on a Medicaid waiting list, with winners allowed to apply for a slot. The OHIE researchers took advantage of this natural experiment to assess the effect of winning the lottery on the 74922 lottery participants. Many lottery winners did not enroll in Medicaid, and 14.1% of lottery losers obtained Medicaid through other routes (some also got private coverage). Hence, the difference in the dose of Medicaid coverage was modest: an absolute difference of about 25%. To adjust for this, the OHIE researchers multiplied outcome differences by about 4 (10). At 1 year of follow-up, the death rate among lottery losers was 0.8%, and the death rate among the winners was 0.032% lower, a dose-adjusted difference of 0.13 percentage points annually (17). This difference was not statistically significant, an unsurprising finding given the OHIE's low power to detect mortality effects because of the cohort's low mortality rate, the low dose of insurance, and the short follow-up. The findings on other health measures, obtained from in-person interviews and brief examinations on a subsample of 12229 individuals in the Portland area, help inform the mortality results. Most physical health measures were similar among lottery winners and losers in the subsample. However, winners had better self-rated health, were more likely to have diabetes diagnosed and treated with medication, and were much less likely to screen positive for depression (10). Medicaid coverage was associated with a nonsignificant decrease of 0.52 (95% CI, 2.97 to 1.93) mm Hg in systolic blood pressure and 0.81 (CI, 2.65 to 1.04) mm Hg in diastolic blood pressure (10). In addition to the low dose of insurance, these wide CIs reflect the lack of baseline blood pressure data; this precludes analyses that take advantage of paired measures on each individual, which would reduce the variance of estimates. In sum, the OHIE yields a (nonsignificant) point estimate that Medicaid coverage reduced mortality by 0.13 percentage points, equivalent to a (nonsignificant) odds ratio of 0.84. Two older RCTs are also relevant to the effect of insurance and access to care on mortality, although neither directly compared insured and uninsured persons. In the RAND Health Insurance Experiment, random assignment to full (first-dollar) coverage reduced diastolic blood pressure by an average of 0.8 mm Hg (P< 0.05) relative to persons randomly assigned to plans that required cost sharing (18), an effect size similar to the blood pressure findings in the OHIE. Unlike the OHIE, the RAND Health Insurance Experiment obtained baseline blood pressure readings, allowing researchers to determine that for participants with hypertension at baseline, full coverage reduced diastolic blood pressure by 1.9 mm Hg, mostly because of better hypertension detection (19); the effect was larger among low-income (3.5 mm Hg) than high-income (1.1 mm Hg) participants (19). The Hypertension Detection and Follow-up Program also suggests that removing financial barriers to primary care in populations with high rates of uninsurance may reduce mortality. That population-based RCT carried out in the 1970s screened almost all residents of 14 communities, with oversampling of predominantly black and poor