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Lifetime Costs of Complications From Type 2 Diabetes

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Diabetes affects an estimated 10.2 million Americans. A study by the American Diabetes Association (ADA) estimated the direct costs of diabetes to be $44.1 billion in 1997, and as the prevalence of diabetes has been increasing, the demand for medical care will continue to increase. As a result of evidence that intensive blood glucose control can reduce the risk of microvascular complications, ADA guidelines indicate that glycemic control is an important goal of treatment. Postprandial hyperglycemia, which is a determinant of glycemia, and the degree of albuminuria are associated with an increased risk of cardiovascular disease and death. Unfortunately, although hypoglycemic agents achieve an initial reduction, glycemic levels tend to drift upward over time. Moreover, many patients are not reaching the recommended treatment goals.

In this study, we provide estimates of the costs of managing the complications of diabetes over time. We relate these costs to the level of glycemia and also explore the impact of its upward drift. The impact of other risk factors, such as hypertension and hypercholesterolemia, is also taken into account

The direct medical costs (in 2000 U.S. dollars) of treating each complication were estimated, excluding the routine costs of managing diabetes (such as home monitoring or supplies) and preventive screening. All event costs include acute care (initial management in inpatient or outpatient setting) and subsequent care in the first year, consisting of subacute inpatient care (i.e., rehabilitation, skilled and intermediate care nursing facilities, chronic hospitals), home health care, outpatient therapy, physician visits, and diagnostic and therapeutic procedures. State costs reflected annual resource use beyond the first year.

A cohort of 10,000 patients with diabetes was simulated using a model based on existing epidemiological studies. Complication rates were estimated for various stages of macrovascular disease, nephropathy, retinopathy, neuropathy, and hypoglycemia. At the beginning of the simulation, patients were assumed to have been treated for 5 years and have a mean HbA_1c of 8.4. From the U.K. Prospective Diabetes Study, it was estimated that on current therapies, the HbA_1c would drift upward on average 0.15% per year. Direct medical costs of managing each complication were estimated (in 2000 U.S. dollars) from all-payor databases, surveys, and literature.

The management of complications generates substantial costs in type 2 diabetes. Macrovascular disease is the major component of these costs, and they are incurred much earlier than those due to managing microvascular complications. Therefore, reduction of the risks of macrovascular complications should also ease the costs of complications. Whether this results in net savings will depend on the cost of the treatment strategy used to achieve the lower risks. This strategy should address risk factors for cardiovascular disease such as smoking, high blood pressure, and hypercholesterolemia; it is not yet certain that improved glycemic control will also help, but recent epidemiological evidence suggests that macrovascular disease is related to postprandial glucose.

This simulation of the course of the disease demonstrates the dependency of costs of treating diabetes-related complications on glycemic level—at both the starting point and the degree of deterioration over time. The costs increase considerably with relatively small increases in HbA_1c, and these escalate faster at higher levels. Moreover, the rate at which glycemia increases over time has an important effect.

There is evidence that, in practice, many patients do not currently achieve or sustain the level of glycemic control (HbA_1c <7%), blood pressure, or cholesterol levels recommended by the ADA. For example, in one study of patients with type 2 diabetes treated with oral agents, 38% achieved the target level of <7%, but 42% of patients had levels >8%. Our analysis shows that, apart from the potential devastating health consequences, this failure to control hyperglycemia has a major economic impact. Therefore, it is important economically to reduce complication rates by reviewing HbA_1c control and introducing changes to the health care processes to ensure that appropriate additions to drug therapy are made promptly so the ADA limits are more frequently achieved and maintained.

Several important assumptions were made for these analyses. Two key assumptions were that complication rates and survival are related to glycemic levels. The relation between HbA_1c and the risk of developing microvascular complications has been convincingly demonstrated in the Diabetes Control and Complications Trial and confirmed in type 2 diabetes by the UKPDS. Several studies support the assumption that survival is dependent on age and sex as well as the patient’s nephropathy state.

Similarly, the degree of albuminuria has been found to predict the development of cerebrovascular and cardiovascular disease. Patients with type 2 diabetes also present other important risk factors for cardiovascular disease, such as high blood pressure and cholesterol levels, and these were considered in the model using data on U.S. patients with diabetes.

Complications have been shown to be an important component of the excess direct medical costs of treating patients with diabetes. Additional support for the analyses is provided by the finding that the costs of managing complications over 10 years were actually found to be reduced in patients with type 2 diabetes receiving intensive treatment rather than conventional therapy. Other shorter-term studies have also concluded that the costs of medical care are increased if HbA_1c levels exceed 7% or 8% and that a reduction from a baseline level of HbA_1c of 10% by at least 1% or more that was sustained over 2 years is associated with lower costs.

As macrovascular disease costs arise early and represent the major component of lifetime costs. Improving control of known risk factors for cardiovascular disease has an enormous potential for reducing the risk of developing complications and lowering health care costs associated with those complications. The net economic impact will depend on the costs of these treatment strategies, which may use more resources than conventional therapy.

The results showed—Macrovascular disease was estimated to be the largest cost component, accounting for 85% of cumulative costs of complications over the first 5 years. The costs of complications were estimated to be $47,240 per patient over 30 years, on average. The management of macrovascular disease is estimated to be the largest cost component, accounting for 52% of the costs; nephropathy accounts for 21%, neuropathy accounts for 17%, and retinopathy accounts for 10% of the costs of complications.

CONCLUSIONS—The complications of diabetes account for substantial costs, with management of macrovascular disease being the largest and earliest. If improving glycemic control prevents complications, it will reduce these costs.

Diabetes Care 25:476-481, 2002

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