Predictors of Health Care Costs in Adults With Diabetes

Gilmer TP, O’Connor PJ, Rush WA, et al. Diabetes Care. 2005;28:59-64.

The cost of health care is significantly higher for persons with diabetes than for persons without diabetes. These higher costs may be attributed to outpatient care, hospitalization, drugs, the greater prevalence of cardiovascular disease (CVD) in persons with diabetes. A previous study of the relationship of health care costs to A1C levels and to CVD concluded that CVD was a stronger predictor of the use of health care resources than was the level of glycemic control. This conclusion was based upon data from 1992 to 1996.

The current study prospectively analyzed 1999-2002 data relating health care costs to several factors including: (1) baseline A1C, (2) duration of diabetes, (3) presence of comorbid chronic conditions, including coronary heart disease (CHD), hypertension, dyslipidemia, and depression, and (4) socioeconomic status. It was hypothesized that increased costs would be associated with factors 1, 2, and 3.

The analysis sample comprised 1,694 persons with diabetes who were members of HealthPartners, a Minnesota health plan. Their A1C values were recorded at baseline; the mean A1C was 7.5%. Their status with regard to diabetes and CHD was obtained from medical records; and their status with regard to hypertension, dyslipidemia, depression, duration of diabetes, education, and income was self-reported.

Throughout the 3-year study, participants received medical care in 84 clinics within 18 medical groups that service members of HealthPartners. Consistency in pricing was achieved by using payment rates standard for Medicare.

In examining the main variable of interest, A1C, the authors found that A1C>7.5% was significantly associated with increased health care cost but A1C<7.5% was not. CHD, hypertension, and depression were also associated with increased cost, but dyslipidemia and duration of diabetes were not. Overall, the difference in costs over the 3-year period for those with A1Cs of 6% and 10% was $2,536 (P<.05). This cost differential was greatest for those with diabetes, hypertension, and CHD ($4,935) and least for those without hypertension or CHD ($1,486). Total costs were greater for those with CHD and hypertension ($46,897) compared with those without CHD or hypertension ($14,233). Individuals reporting depression cost more than those without depression (P<.05).

These results indicate that although A1C levels (over 7.5%) are an independent predictor of future health care costs, CHD, hypertension, and depression are even more significant independent predictors of future costs in persons with diabetes. These data do not, however, prove that treatment of these conditions will reduce costs. Thus, while continuing to aggressively manage A1C, clinicians should put more emphasis on prevention and management of CHD, hypertension, and depression to control health care costs in persons with diabetes.