Risk score for prediction of 10 year dementia risk in individuals with type 2 diabetes: a cohort study

Abstract

Background: Although patients with type 2 diabetes are twice as likely to develop dementia as those without this disease, prediction of who has the highest future risk is difficult. We therefore created and validated a practical summary risk score that can be used to provide an estimate of the 10 year dementia risk for individuals with type 2 diabetes.

Methods: Using data from two longitudinal cohorts of patients with type 2 diabetes (aged ≥60 years) with 10 years of follow-up, we created (n=29,961) and validated (n=2413) the risk score. We built our prediction model by evaluating 45 candidate predictors using Cox proportional hazard models and developed a point system for the risk score based on the size of the predictor's β coefficient. Model prediction was tested by discrimination and calibration methods. Dementia risk per sum score was calculated with Kaplan-Meier estimates.

Findings: Microvascular disease, diabetic foot, cerebrovascular disease, cardiovascular disease, acute metabolic events, depression, age, and education were most strongly predictive of dementia and constituted the risk score (C statistic 0·736 for creation cohort and 0·746 for validation cohort). The dementia risk was 5·3% (95% CI 4·2-6·3) for the lowest score (-1) and 73·3% (64·8-81·8) for the highest (12-19) sum scores.

Interpretation: To the best of our knowledge, this is the first risk score for the prediction of 10 year dementia risk in patients with type 2 diabetes mellitus. The risk score can be used to increase vigilance for cognitive deterioration and for selection of high-risk patients for participation in clinical trials.

Funding: Kaiser Permanente Community Benefit, National Institute of Health, Utrecht University, ZonMw, and Fulbright.

Figure 1

Flow-chart of the analytic steps of creating the DSDRS.

Figure 2

Summary of the diabetes-specific dementia risk score According to the figure, a 71-year-old man with a university degree and a medical history of diabetes type 2, diabetic retinopathy, and myocardial infarction would have a diabetes-specific dementia risk score of 6 points and therefore a 34% risk of dementia in the next 10 years; an 86-year-old woman with a high-school education and type 2 diabetes and depression would have a risk score of 11 points and a 66% risk of dementia in the next 10 years; and a 61-year-old man who did not complete high school, and had type 2 diabetes, diabetic foot, several hospital admissions for severe hypoglycaemic events, a stroke, and depression would have a risk score of seven points and a 40% risk of dementia in the next 10 years.

Figure 3. Observed dementia risk (DR) per sum score (SS) stratified by age groups

Mean points (±SD). Pnumber represents percentiles, P90 is 90th percentile. Shown is the distribution based on the number of subjects with a certain amount of points. The associated dementia risk (DR) based on Kaplan-Meier estimates per sum score of the diabetes specific dementia risk score (DSDRS) is reported.

Figure 4

Ten year dementia risk by levels of DSDR categories in the development cohort