Improvements in risk factor control among persons with diabetes in the United States: evidence and implications for remaining life expectancy

Presenter: Thomas Hoerger, RTI International

Abstract

Background. Glycemic, hypertension, and cholesterol control are key components of care for type 2 diabetes. We examined whether A1c, blood pressure, and cholesterol values changed for U.S. adults with diagnosed diabetes between 1988–1994 and 2005–2006. We then projected the impact of these changes on life expectancy and diabetes-related complications.

Methods. We estimated the change in hemoglobin A1c, blood pressure, and total cholesterol between 1988–1994 and 2005–2006 using regression analysis and data on U.S. adults with diagnosed diabetes from the National Health and Nutrition Examination Survey (NHANES). Using the estimated changes in these variables, we projected the potential effects on life expectancy and complications using the CDC-RTI Diabetes Cost-Effectiveness Model. We also consider the effects on the lifetime costs of diabetes complications.

Findings. During the period, A1c fell by 0.68 percentage points (P = .001) among U.S. adults with diagnosed diabetes. Among those with diabetes and hypertension, systolic and diastolic blood pressure fell by 5.66 and 8.15 mmHg, respectively (P = .005 and P = .001). Among those with diabetes and high cholesterol, total cholesterol fell by 36.41 mg/dL (P = .001). These improvements were projected to increase life expectancy for persons with newly diagnosed diabetes by 1.0 year due to relative reductions in the cumulative incidence of end-stage renal disease, lower extremity amputations, and coronary heart disease. Improved cholesterol values accounted for the largest share of this improvement, followed by A1c.

Interpretation. Risk factor control has improved. Persons newly diagnosed with type 2 diabetes in 2005 have a better prognosis than persons diagnosed with diabetes 11 years earlier. However, because persons with diabetes have lower life expectancy than persons without diabetes, recent increases in diabetes incidence will tend to lower overall life expectancy in the population, holding risk factor control constant. The large incidence trends are likely to more than offset the improved risk factor effects observed during the study period. This observation reinforces the importance of both secondary prevention of diabetes complications for persons with diabetes and primary prevention of incident diabetes in at-risk persons. Efforts to improve modifiable risk factors for persons with diabetes should continue and receive encouragement from the improvements reported in this study. At the same time, primary prevention could decrease the incidence of new cases.