Dementia risk prediction in the general population: external validation of a prediction model in the LifeLines Cohort Study

Objective: Models for dementia prediction in primary care are necessary to be able identify individuals at risk for developing dementia, but their implementation in clinical practice is limited due to the lack of their external validation or use of high-cost variables. We evaluated the external performance of the basic dementia risk prediction model developed in the Rotterdam Study for application in primary care settings.
Methods: Applying the model developed in the Rotterdam Study, predictive performance was assessed with a c-statistic with 95% confidence interval, using age, history of stroke, subjective memory complaints and need for assistance with a relatively complex task as predictors. This was done on 10007 individuals that participated in the Lifelines-cohort study. 
Results: Mean follow-up at timepoint 1b was 1.5 years, mean follow-up at timepoint 2a was 3.3 years and mean follow-up at timepoint 3a was 9.1 years, overall 36 participants reported dementia development. Discriminative ability of the model overall dementia development yielded a c-statistic of 0.62 [95% CI=0.48-0.70], and performed slightly better at follow-up 2a 0.67 [95% CI=0.57-0.78]. The model performed better for women than for men, with overall c-statistics of 0.70 [95% CI=0.54-0.81] and 0.43 [95% CI=0.42-0.68], respectively.
Conclusion: In this study the basic dementia risk prediction model overestimated the risk of dementia, but had reasonable discriminative ability in the Lifelines cohort. The use of questionnaire information to predict risk make this model a very simple and accessible tool that could be used in a primary care setting.