Mortality Rates in Alzheimer's Disease and Non-Alzheimer's Dementias: A Systematic Review and Meta-Analysis

Abstract

Background: People with dementia die prematurely. Identifying differences in mortality rates between different types of dementia may aid in the development of preventive interventions for these most vulnerable populations. Methods: A systematic search of the MEDLINE, PubMed, EMBASE, and Cochrane Library from inception to May 31, 2020 was conducted for case-control or cohort studies providing mortality and survival-related outcomes among people with different types of dementia. The primary outcomes were the all-cause mortality rate and survival time from dementia diagnosis between the general population, people with Alzheimer’s disease (AD), and those with non-AD dementias. The secondary outcomes were age at death and survival time from disease onset. Random-effects meta-analyses were conducted. Effect sizes included hazard ratios (HRs) and mean differences (MDs) with 95% confidence intervals (CIs). Potential moderators were identified through meta-regression and subgroup analyses. The Newcastle Ottawa Scale was used to measure the methodological quality of eligible studies. Heterogeneity was assessed with the I2 statistic and sensitivity analyses were undertaken. Findings: Data were extracted from 78 eligible studies encompassing 152,353 controls and 63,125 cases of dementia. All-cause mortality occurred in 20,927 of 152,174 controls and in 2,684 of 8,102 cases of dementia during a median 5-year follow-up. After diagnosis, the median survival time for people with AD was 4·4 (range, 1·3, 10) years. Compared to controls, the HR of all-cause mortality was highest for Lewy body dementia (17·88; 95% CI, 5·87, 54·46). Compared to AD, a diagnosis of any non-AD dementia was associated with a higher risk of all-cause mortality (HR, 1·33; 95% CI, 1·21, 1·46), a shorter survival time from diagnosis (MD, -1·12; 95% CI, -1·52, -0·72), and a younger age at death (MD, -1·76; 95% CI, -2·67, -0·85). However, group differences between distinct subtypes of non-AD dementia were not significant. Interpretation: AD is the most common type of dementia and the leading cause of mortality world-wide, but non-AD dementias have a worse prognosis in terms of mortality and survival. Funding: None to declare. Declaration of Interest: None to declare