To the authors' knowledge, this is the first national level study of the impact of state mandatory diabetes insurance coverage on the use of diabetes preventive care. Our findings suggest that state mandates vary in their impact by preventive care type, but the impact tends to be small.
The effects of state mandates were smaller than other policies expanding insurance coverage for patients with diabetes. Li et al. analyzed the effect of the Medicare expansion on diabetes monitors and strips to non-insulin users in 1997; the probability of diabetes non-insulin users' performing daily SMBG increased by 6-16 percentage points after the expansion [21
]. Karter et al. reported a 16 percentage point increase in performing daily SMBG and an 8 percentage point increase in annual eye exams among diabetes patients in a large managed care organization after it changed its reimbursement policy from no coverage to only paying a small amount of copayment for strips and eye exams [22
One possible reason for the limited effect of mandates is that many insurance policies already covered the mandated benefits even without mandates in place; accordingly a relatively small number of people were directly benefitted. As an extreme example, a 2003 report by the Utah Insurance Department showed that, prior to the passage of Utah's 2000 law requiring insurers to cover diabetic monitors and blood testing strips, all insurance plans in the state already provided such coverage [23
]. Although self-insured health plans were exempt from the mandates, a GAO report (2005) showed that the policies in 13 of the largest employers self-insured health plans covered most of the mandated benefits [13
]. We are aware of no evidence that the benefit coverage of the self-insured health plans are more generous than the other private insurance policies, which the state mandates would impact. The GAO report also attributed the small number of states mandating periodical eye and foot exams to these forms of care being considered part of general health care, and therefore already covered [13
Another possible reason for the limited effect is that unpublished work from the CDC indicates that 30%-50% of Americans with diabetes work for employers that are exempted from state mandates (self-insured organizations or the federal government); however, our data source does not allow us to identify these people. Considering the larger size of the effect of similar mandates in the Medicare population, we would probably have found larger effects here had our data sources allowed us to restrict our analyses to those whose employers were subject to state mandates and whose insurance did not cover these preventive care before the mandates [21
The state mandates were not shown to have an effect on annual eye and foot exams, which was consistent with our hypothesis that the direct effect of state mandates would be limited. However, we also found no evidence for the hypothesized indirect effects through increased knowledge. One possible explanation is that annual eye and foot exams, unlike SMBG, require more effort from health providers than from the patients, and state mandates do not directly affect providers' practice pattern, although the mandates reduced the burden of filing paperwork claiming authorization[24
]. Ceiling effects may also play a role: 63% and 59% percent of patients had received annual eye exams and foot exams before the state mandates, respectively, while only 44% performed SMBG daily. The effect of expanding insurance coverage in further increasing the proportion of patients receiving annual eye exams and foot exams might be limited. Other strategies might be considered.
Direct (mandating benefit coverage) and indirect (the effect achieved through increased knowledge obtained via DSME) effects could not be isolated, and our data did not allow us to determine whether the expanded DSME coverage actually resulted in an increase in patients taking DSME classes. All but one of the states that passed mandates between 1997 and 1999 covered DSME. DSME classes often include material concerning the importance of performing SMBG and receiving annual eye and foot exams to prevent diabetic complications [25
]. Prior to the mandates being passed, coverage of DSME was unusual. For example, a study in 1994 reported that only 35.1% of the US adult population with diabetes attended any diabetes classes or programs, primarily due to lack of reimbursement [26
]. However, our results suggest that the effects of DSME classes during the study period might be limited. This could be due to how the mandates on DSME were implemented: many mandates included restrictions on who should receive the benefits and who could be reimbursed for providing DSME [25
]. Thus the benefits of mandated coverage on DSME might not be realized in the initial years after the mandates passed.
Members of racial and ethnic minorities and low income persons could plausibly be more likely than others to be underinsured, therefore, they might benefit more from the mandates. When we examined interaction terms between the variables indicating presence of a mandate and the variables indicating membership in these groups, the coefficients of the interaction terms were positive. This suggested that the state mandates might have had more effect on use of the preventive care in people who were underinsured and less likely to have these coverage before the state mandates. However, the interactions were not significant. Because these sub-groups were represented by small sample sizes, we had little power to detect interactions. Thus, it remains unknown if mandates are truly more effective in the case of underinsured persons.
Our results show that state mandates increased the probability of people with diabetes receiving all three types of preventive care simultaneously. This is important because diabetic patients need comprehensive care. From the size of the coefficients, this could plausibly be due to improved SMBG among people who received eye and foot exams. It is possible that those who did not receive annual eye or foot exams prior to the mandates (the group that most needs to be motivated to receive preventive care) were not motivated by changes in insurance coverage.
Our study has several limitations. First, our results only apply to the states included in the analysis and the three types of preventive care. The results might or might not generalize to other states and other types of care, such as DSME or prescription drugs. Second, we did not have information on how state mandates were implemented. Third, the cross-sectional nature of the data does not allow us to make causal inferences. Fourth, if there were other confounding state time-variant characteristics, our estimation might be biased. Fifth, although we used time trend to control the effects of national programs such as NCQA report cards and other diabetes quality improvement initiatives, if the effects of these programs differed among the states, our results might be confounded. Finally, our study also inherited the limitations of the BRFSS. For example, BRFSS data are self-reported; BRFSS is a land telephone-based surveillance system, excluding those without land-based telephones.
Although state mandates might have improved receipt of diabetes-related preventive care little or none, we do not advocate that mandates be repealed. Following the 1990's shrinkage of benefits covered by managed care health plans and the failure of the health care reform, state mandates were more and more used as a political force to push the problem in health care system onto the policy agenda and show that government can take action. One state's mandates can also serve as precedents for others [9
]. This symbolic effect can be very powerful: during 1996-2003, 43 states and District of Columbia passed state mandates on diabetes benefits. The early state mandates may have contributed to the expansion of Medicare's coverage of diabetes in 1997 [7
]. Thus the state mandates could contribute indirectly to the improvement of the diabetes care, along with the other programs such as NCQA quality report card and the state diabetes prevention and control programs. In addition, small increases in rate of utilization, over time, can add up. Since we do not know what happened after our study period, it is possible that the small increase in performing daily SMBG that we detected might, eventually, have a positive impact on public health. Furthermore, opponents of state mandates have claimed that mandates would increase insurance premiums, causing employers to drop insurance and leave more people uninsured[28
]. Our analysis showed that state mandates had a small impact on using the covered benefits. Thus, it is unlikely that more than a handful of employers would drop insurance coverage due to state mandates.