This report reviews the scientific evidence for intensive therapy aimed at lowering blood glucose levels to near normal in patients with type 1 and type 2 diabetes. In diabetes, risks for diabetic complications are associated with high average blood glucose levels as measured by HbA_1c. Hence, in treating diabetes it is natural to aim at lowering HbA_1c to normal or near normal levels. In type 1 diabetes, we refer to this as intensive insulin therapy. Since several different types of drugs are used to treat type 2 diabetes we refer to this as intensive glucose-lowering therapy. The report was commissioned by the Swedish National Board of Health and Welfare (NBHW) to provide a foundation for their national guidelines for diabetes care. Within the framework of the NBHW guidelines program, SBU is producing three additional reports addressing patient education in managing diabetes, self-monitoring of blood glucose in noninsulin-treated diabetes, and dietary treatment of diabetes.

Conclusions

• Intensive insulin therapy for type 1 diabetes is demanding for health services and the patient alike, but reduces the risk for cardiovascular disease and substantially reduces the risk for damage to the retina, kidneys, and nerves. The risk is increased for serious hypoglycemia, which places the greatest limitation on treatment. In many patients, successful intensive therapy should reduce diabetes complications in the long term. Treatment is cost effective.
• In newly diagnosed type 2 diabetes, intensive glucose-lowering therapy helps reduce the risk of cardiovascular disease and serious damage to the retina of the eye. Treatment is relatively simple, and the risks for side effects are small. Successful intensive therapy of newly diagnosed type 2 diabetes should reduce such complications in the long term. Treatment is cost effective.
• In patients who have had type 2 diabetes for 5 to 10 years, or longer, the benefits of intensive glucose-lowering therapy are not uniformly greater than the risks, and the cost effectiveness is not clear. The risk for kidney damage is somewhat reduced. Studies present conflicting findings regarding the risk for cardiovascular diseases. It is important to individualize the treatment goals for these patients and balance the risks of side effects (e.g., serious hypoglycemia) against the risks of late diabetes complications, which increase with the rise in HbA_1c. New studies with longer follow-up are urgently needed in this patient group.

Results Intensive insulin therapy in type 1 diabetes Microvascular disease

• Intensive insulin therapy in type 1 diabetes reduces the risk for complications in the eyes, kidneys, and nerves (microvascular disease). The absolute effect is large, approximately 2 to 3 fewer cases per 10 patients during 7 years of treatment (strong scientific evidence).

Cardiovascular disease

• Intensive insulin therapy in type 1 diabetes reduces the risk for cardiovascular disease in the long term (limited scientific evidence).

Risks / side effects

• The risk for serious hypoglycemia increases with intensive insulin therapy for type 1 diabetes (strong scientific evidence). The risks increase substantially, approximately 3 times.
• Intensive insulin therapy in type 1 diabetes increases the risks for weight gain (strong scientific evidence).
• Intensive insulin therapy in type 1 diabetes does not appear to affect quality of life during a 6-year period (limited scientific evidence).

Health economics

• Intensive insulin therapy in type 1 diabetes involves low to moderate costs per quality-adjusted life-year (QALY) and is cost effective.