Impact of impairment in instrumental activities of daily living and mild cognitive impairment on time to incident dementia – results of the Leipzig Longitudinal Study of the Aged (LEILA75+)

Background: Early diagnosis of dementia requires knowledge about associated predictors. The aim of this study was to determine the impact of mild cognitive impairment (MCI) and impairment in instrumental activities of daily living (IADL) on the time to an incident dementia diagnosis. Methods: Data were derived from the Leipzig Longitudinal Study of the Aged (LEILA75+), a population-based study of individuals aged 75 years and older. Kaplan-Meier survival analysis was used to determine time to incident dementia. Cox proportional hazards models were applied to determine the impact of MCI and impairment in IADL on the time to incident dementia. Results: 180 (22.0%) of 819 initially dementia-free subjects developed dementia by the end of the study. Mean time to incident dementia was 6.7 years (95% CI=6.5–6.9). MCI combined with impairment in IADL was associated with a higher conversion rate to dementia and a shorter time to clinically manifest diagnosis. The highest risk for a shorter time to incident dementia was found for amnestic MCI combined with impairment in IADL: the mean time to incident dementia was 3.7 years (95% CI=2.9–4.4) and thus half as long as in subjects without MCI and impairment in IADL. Conclusions: Subjects with MCI and impairment in IADL constitute a high-risk population for the development of dementia. The consideration of impairment in IADL should constitute an important step towards an MCI concept being clinically more useful for prediction of dementia.