Health care markets, the safety net, and utilization of care among the uninsured

Health Services Research, Feb, 2007 by Carole Roan Gresenz, Jeannette Rogowski, Jose J. Escarce

Multivariate Analyses

Tables 5 and 6 show predicted annual utilization among the rural and urban uninsured, respectively, for simulation values of each of the safety net and health care market variables. (Full regression results are available from the authors upon request.) As an example of how to interpret the values in these tables, the first row of Table 5 indicates that if all uninsured individuals living in rural areas had an ED approximately a mile away (the 25th percentile value of the distribution), the average number of annual physician visits would be 1.82. By comparison, if the rural uninsured all lived significantly farther away from the ED (13 miles, the 75th percentile value), annual physician visits would average 1.62. Tables 7 and 8 report predictions for sensitivity analyses using radius-based measures of the availability of safety net providers.

All of the underlying regressions include socio-demographic and health status/health condition controls. Though our main focus is on the safety net and health care market variables, findings related to the individual-level variables include the following: A higher level of education is associated with more office-based visits, fewer ED visits, and a greater probability of any medical expenditures; being married and being a woman are both associated with more office-based visits and a greater probability of any medical expenditures; being a minority is associated with a lower probability of any medical expenditures; and the presence of chronic health conditions is associated with more utilization, as is a self-reported health status of poor or fair compared with good to excellent.

Rural Uninsured

The analyses of utilization among the rural uninsured provide support for both own-price and cross-price effects of distances to various safety net providers on utilization. First, we observe an own price effect of distance to the closest migrant health center, community health center, or public housing primary care program (BPHC provider), with a longer distance resulting in fewer office-based physician and nonphysician visits (Table 5). These results are consistent with our hypothesis that a higher time-price of obtaining care from a safety-net provider decreases utilization of health care among the uninsured. In the regressions using radius-based measures (Table 7), a greater number of BPHC providers within a 10-mile radius is associated not only with the frequency of office-based visits, but also with a higher probability of any medical expenditures or charges. In some cases, the differences in utilization observed are statistically significant but relatively small in magnitude. It is difficult to know whether these relatively small differences are also significant in a clinical sense.

Second, we find a cross-price effect of distance to the nearest ED on physician visits (Table 5). We observe an inverse relationship, with longer distances to the ED associated with fewer physician visits, suggesting that office-based visits are complementary with use of the ED. Individuals may follow-up an ED visit with a physician visit, perhaps because an ED doctor refers a patient to a provider. The own-price association we observe of distance to the nearest ED on ED visits is consistent with our a priori expectation (longer distances associated with fewer ED visits), but surprisingly, the relationship is not statistically significant. However, the regression using the radius-based measures (Table 7) shows the statistically significant finding that a greater number of EDs within 10 miles is associated with more ED visits (as well as a greater number of office-based physician visits).