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

https://doi.org/10.1016/S2213-8587(13)70048-2Get rights and content

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.

Introduction

The rising prevalence of type 2 diabetes is of great public health concern, especially because this disease can lead to complications in several organ systems. Over the past decades, patients with type 2 diabetes have been living longer because of major improvements in treatment and demographic trends.1 This improved longevity is, however, accompanied by an increased risk of health complications associated with ageing, including cognitive impairment and dementia.2 Adults with type 2 diabetes have a roughly doubled risk of dementia—both Alzheimer's disease and vascular dementia—compared with those who do not have type 2 diabetes.3

Despite substantial efforts, there is no effective treatment to cure or prevent dementia. In recent years, attention has focused on early intervention strategies at a stage when there is still time and potential to modify disease progression.4, 5 Nevertheless, the findings of prevention trials have not yet shown the desired effect. To increase the success of future trials, enrichment of study cohorts through risk stratification has been recommended.4 A similar approach in which risk scores are used for selection of people for targeted treatment has been used successfully for cardiovascular diseases.6, 7 Recently, several risk scores for prediction of the risk of dementia have been reported.8, 9, 10, 11 However, none of these scoring systems account for diabetes-specific dementia predictors, such as diabetes duration, glucose lowering treatment, and severe hypoglycaemic episodes.12, 13, 14, 15, 16, 17, 18 Because people with type 2 diabetes are particularly susceptible to dementia, identification of those at high risk in early stages of the dementia process when symptoms are still subclinical is crucial in this population. Our aim in this study was to develop and validate a score that can be easily implemented in daily clinical care to predict the 10 year dementia risk in older individuals with type 2 diabetes.

Section snippets

Patients and study design

For the development of the risk score, we evaluated data for 29 961 patients (aged ≥60 years) with type 2 diabetes from the Kaiser Permanente Northern California (KPNC) Diabetes Registry, Oakland, CA, USA. The data for this well characterised cohort of patients with type 2 diabetes have been used in several epidemiological and health services studies18, 19, 20, 21 since 1994, as part of the Diabetes and Aging Study.19 KPNC is a large, integrated health-care delivery system providing

Results

Table 1 shows the baseline characteristics; the mean age of the development cohort (n=29 961) was 70·6 years (SD 6·8), 46% were women, and 45% of individuals were educated to college or higher level. The highest educational level was college or higher. The population was ethnically diverse, with 37% non-white patients. Mean diabetes duration at baseline was 11·6 years (9·5). 5173 (17%) patients received a diagnosis of dementia during 6·6 years (3·4) of follow-up. During follow-up 14 366 (48%)

Discussion

The DSDRS presented in this report is predictive of an individual's absolute risk of developing dementia within the subsequent decade based on the predictors diabetes-related comorbidities and complications, age, and education. The predictive accuracy of the DSDRS in the development and validation cohort was similar. The DSDRS stratifies individuals into 14 categories from −1 to 12–19, showing a 15 times difference in dementia risk between the lowest and the highest sum scores; it performs well

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