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Objective: Progression from cognitive impairment (CI) to dementia is predicted by several factors, but their relative importance and interaction are unclear., Method: We investigated numerous such factors in the AgeCoDe study, a longitudinal study of general practice patients aged 75+. We used recursive partitioning analysis (RPA) to identify hierarchical patterns of baseline covariates that predicted dementia-free survival., Results: Among 784 non-demented patients with CI, 157 (20.0%) developed dementia over a follow-up interval of 4.5 years. RPA showed that more severe cognitive compromise, revealed by a Mini-Mental State Examination (MMSE) score < 27.47, was the strongest predictor of imminent dementia. Dementia-free survival time was shortest (mean 2.4 years) in such low-scoring patients who also had impaired instrumental activities of daily living (iADL) and subjective memory impairment with related worry (SMI-w). Patients with identical characteristics but without SMI-w had an estimated mean dementia-free survival time of 3.8 years, which was still shorter than in patients who had subthreshold MMSE scores but intact iADL (4.2-5.2 years)., Conclusion: Hierarchical patterns of readily available covariates can predict dementia-free survival in older general practice patients with CI. Although less widely appreciated than other variables, iADL impairment appears to be an especially noteworthy predictor of progression to dementia., (© 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Background. As physical activity may modify the effect of the apolipoprotein E (APOE) ϵ4 allele on the risk of dementia and Alzheimer's disease (AD) dementia, we tested for such a gene-environment interaction in a sample of general practice patients aged ⩾ 75 years. Method. Data were derived from follow-up waves I-IV of the longitudinal German study on Ageing, Cognition and Dementia in Primary Care Patients (AgeCoDe). The Kaplan-Meier survival method was used to estimate dementiaand AD-free survival times. Multivariate Cox regression was used to assess individual associations of APOE ϵ4 and physical activity with risk for dementia and AD, controlling for covariates. We tested for gene-environment interaction by calculating three indices of additive interaction. Results. Among the randomly selected sample of 6619 patients, 3327 (50.3%) individuals participated in the study at baseline and 2810 (42.5%) at follow-up I. Of the 2492 patients without dementia included at follow-up 1,278 developed dementia (184 AD) over the subsequent follow-up interval of 4.5 years. The presence of the APOE ϵ4 allele significantly increased and higher physical activity significantly decreased risk for dementia and AD. The co-presence of APOE ϵ4 with low physical activity was associated with higher risk for dementia and AD and shorter dementia- and AD-free survival time than the presence of APOE ϵ4 or low physical activity alone. Indices of interaction indicated no significant interaction between low physical activity and the APOE ϵ4 allele for general dementia risk, but a possible additive interaction for AD risk. Conclusions. Physical activity even in late life may be effective in reducing conversion to dementia and AD or in delaying the onset of clinical manifestations. APOE ϵ4 carriers may particularly benefit from increasing physical activity with regard to their risk for AD. [ABSTRACT FROM AUTHOR]