Clinical Question: What is the relative benefit of lipid control in patients with diabetes?
Study Design: Decision analysis
Synopsis: This decision analysis used the Cardiovascular Disease Life Expectancy Model to estimate the annual probability of fatal and nonfatal cardiovascular events. Using the third National Health and Nutrition Examination Survey 1988–94, the cardiovascular risk factors in adults who had diabetes were compared with those of adults who had cardiovascular disease but no diabetes. They estimated what would happen if low-density lipoprotein levels were lowered by 35 percent and high-density lipoprotein levels were increased by 8 percent, which is what occurred in the Scandinavian Simvastatin Survival Study.
Using the model, an estimated 25.4 million person-years of life would be saved with lipid control in patients with diabetes, compared with 16 million person-years of life saved in patients with cardiovascular disease. (A person-year is a way to determine lifespan mortality in a group of people, not necessarily an individual. It could equate to one person living one year longer, 12 people living one month longer, or any other combination.)
On average, this benefit translates into 3.0 to 3.4 years of life saved in the average patient with diabetes, compared with 2.4 to 2.7 years of life saved in the average patient with heart disease (the benefit is less because this latter group is more likely to smoke than patients with diabetes). In women with diabetes, controlling lipid levels results in 1.6 to 2.4 years of life saved, compared with 1.6 to 2.1 years in women with heart disease. All of these benefits assume that patients in typical practices will achieve the same degree of lipid control as occurred in the research studies.
Bottom Line: The benefit of controlling lipid levels in patients with type 2 diabetes is at least as valuable as controlling lipid levels in patients with cardiovascular disease. In this model, which used existing data on mortality benefits achievable with therapy, controlling lipid levels in men with diabetes results in 3.0 to 3.4 years of life saved compared with 2.4 to 2.7 years of life saved by controlling lipid levels in men with heart disease. Women with diabetes gain an estimated 1.6 to 2.4 years versus 1.6 to 2.1 years in women with heart disease. Controlling cholesterol levels and blood pressure in patients with type 2 diabetes is much more important than tightly controlling blood glucose levels when it comes to extending life and preventing complications. (Level of Evidence: 2b)