Type 2 diabetes: incremental medical care costs during the 8 years preceding diagnosis.

OBJECTIVE To describe and analyze medical care costs for the 8 years preceding a diagnosis of type 2 diabetes. RESEARCH DESIGN AND METHODS From electronic records of a large group-model health maintenance organization (HMO), we ascertained the medical care costs preceding diagnosis for all members with type 2 diabetes who were newly diagnosed between 1988 and 1995. To isolate incremental costs (costs caused by the future diagnosis of diabetes), we subtracted the costs of individually age- and sex-matched HMO members without impending diabetes from the costs of members who were destined to receive this diagnosis. We also compared these prediagnosis costs with the first 3 years of postdiagnosis costs. RESULTS An economic burden from impending diabetes is apparent for at least 8 years before diagnosis, beginning with costs for outpatient and pharmacy services. Diabetes-associated incremental costs (costs of type 2 diabetic patients minus matched costs of nondiabetic patients) averaged $1,205 per type 2 diabetic patient per year during the first eight prediagnostic years, including $1,913 each year for the 3 years preceding diagnosis. In the year immediately preceding diagnosis, incremental costs were equivalent to those observed in the second and third years after diagnosis. CONCLUSIONS Incremental costs of diabetes begin at least 8 years before diagnosis and grow at an accelerating rate as diagnosis approaches and immediately after diagnosis. These incremental costs span the full range of medical services. Furthermore, the majority of these costs are for conditions not normally associated with diabetes or its complications.