Health Insurance and Mortality in US Adults Part 3

DISCUSSION
The uninsured are more likely to die than are the privately insured. We used a nationally representative data set to update the oft-cited study by Franks et al. and demonstrate the persistence of increased mortality attributable to uninsurance. Our findings are in accord with earlier research showing that lack of health insurance increases the likelihood of death in select illnesses and populations.5–7,13 Our estimate for annual deaths attributable to uninsurance among working-age Americans is more than 140% larger than the IOM’s earlier figure.23

By using methodologies similar to those used in the 1993 study, we found that being uninsured is associated with a similar hazard for mortality (1.40 for our study vs 1.25 for the 1993 study). Although the NHANES I study methodology and population were similar to those used in NHANES III, differences exist. The population analyzed in the original study was older on average than were participants in our sample (22.8% vs 55.6% aged 34 years or younger). The maximum length of follow-up was less (16 years vs 12 years), and the earlier analysis was limited to White and Black persons, whereas the present study also includes Mexican Americans.
The relative youthfulness and shorter follow-up in our study population would be expected to reduce our power to detect an elevated risk of death. In addition, if gaining Medicare reduces the effect of uninsurance on mortality, then the younger age and shorter length of follow-up in our study might strengthen the association between uninsurance and mortality compared with the earlier study. It is less clear how the differences in the racial and ethnic make-up of our study population would affect our ability to detect difference in risk of death. In fact, the increased likelihood of uninsurance among Mexican Americans who were nonetheless no more likely to die than non- Hispanic Whites might also be expected to reduce our power compared with the earlier study.


The original analysis confirmed vital status by review of decedents’ death certificates. The NCHS had developed a probabilistic matching strategy to establish vital status. A subsample underwent death certificate review and verification; 98.7% were found to be correctly classified following this review.16 Again, it is not clear how any misclassification would bias our results. Moreover, Congress extended Medicare coverage in 1972 to 2 nonelderly groups: the long-term disabled and those with end-stage renal disease.27 So, although both studies excluded Medicare enrollees, only ours entirely excluded disabled nonelderly adults who are at particularly high risk of death.

The mechanisms by which health insurance affects mortality have been extensively studied. Indeed, the IOM issued an extensive report summarizing this evidence.29 The IOM identified 3 mechanisms by which insurance improves health: getting care when needed, having a regular source of care, and continuity of coverage.



The uninsured are more likely to go without needed care than the insured. For instance, Lurie et al. demonstrated that among a medically indigent population in California, loss of government-sponsored insurance was associated with decreased use of physician services and worsening control of hypertension.28,29 The uninsured are also more likely to visit the emergency department30 and be admitted to the hospital31 for ‘‘ambulatory care sensitive conditions,’’ suggesting that preventable illnesses are a consequence of uninsurance.

The chronically ill uninsured are also less likely to have a usual source of medical care,32 decreasing their likelihood of receiving preventative and primary care. Discontinuity of insurance is also harmful; those intermittently uninsured are more likely to die than the insured.13 All of these factors likely play a role in the decline in health among middle-aged uninsured persons detected by Baker et al.33,34 This trend appears to reverse at age 65, when the majority gains access to Medicare coverage.35 Other studies suggest that extending health insurance not only improves health, but also may be cost effective.36