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

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. Method Data were derived from the Leipzig Longitudinal Study of the Aged (LEILA75+), a population-based study of individuals aged ⩾75 years. 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 IADL impairment on the time to incident dementia. Results In total, 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% confidence interval (CI) 6.5–6.9]. MCI combined with IADL impairment was associated with a higher conversion rate to dementia, a shorter time to clinically manifest diagnosis and a lower chance of reversibility to cognitive normal. The highest risk for a shorter time to incident dementia was found for amnestic MCI combined with IADL impairment. 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 IADL impairment. Conclusions Subjects with MCI and IADL impairment constitute a high-risk population for future dementia. The consideration of both – MCI and IADL impairment – might help to improve the prediction of dementia.