Dementia, cognitive impairment and mortality in persons aged 65 and over living in the community: a systematic review of the literature

Background No recent attempt has been made to synthesise information on mor tality and dementia despite the theoretical and practical interest in the t opic. Our objective was to estimate the influence on mortality of cognitive impairment and dementia. Methods Data sources were Medline, Embase, personal files and colleagues' r ecords. Studies were considered if they included a majority of persons aged 65 and over at baseline either drawn from a total community sample or draw n from a random sample from the community. Samples from health care facilit ies were excluded. The search located 68 community studies. Effect sizes we re extracted from the studies and if they were not included in the publishe d studies, effect sizes were calculated where possible: this was possible f or 23 studies of cognitive impairment and 32 of dementia. No attempt was ma de to contact authors for missing data. Results For the studies of cognitive impairment Fisher's method (a vote cou nting method), gave a p-value (from eight studies) of 0.00001. For studies of dementia, age-adjusted confidence intervals (CI) were pooled (odds ratio (OR) 2.63 with 95% CI 2.17 to 3.21 from six studies). Conclusions Levels of cognitive impairment commonly found in community stud ies give rise to an increased risk of mortality, and this appears to be tru e even for quite mild levels of impairment. The analysis confirms the incre ased risk of mortality for dementia, but reveals a dearth of information on the causes of the excess mortality and on possible effect modification by age, dementia subtype or other variables. Copyright (C) 2001 John Wiley & S ons, Ltd.