Mortality rates in Alzheimer's disease and non-Alzheimer's dementias: a systematic review and meta-analysis

Background: People with dementia die prematurely. Identifying differences in mortality rates between different types of dementia might aid in the development of preventive interventions for the most vulnerable populations. The aim of this study was to compare the difference in mortality rates between individuals without dementia and individuals with various types of dementia. Methods: For this systematic review and meta-analysis, we did a systematic search of MEDLINE, PubMed, Embase, and Cochrane Library from inception to July 11, 2020, for cross-sectional or cohort studies that assessed mortality and survival-related outcomes among people with different types of dementia compared with people without dementia. Single-arm studies without comparison groups and autopsy studies or family studies that used a selected sample were excluded. The Newcastle-Ottawa Scale was used by two authors (D-JL and C-SC) independently to measure the methodological quality of included studies, and two authors (F-CY and P-TT) independently extracted data. We assessed differences in all-cause mortality rate and survival time from dementia diagnosis between individuals without dementia, individuals with Alzheimer's disease, and individuals with non-Alzheimer's disease dementias. The secondary outcomes were age at death and survival time from disease onset. Random-effects meta-analyses were done. Effect sizes included hazard ratios (HRs) and mean differences (MDs) with 95% CIs. Potential moderators, including age-associated moderators, were identified through meta-regression and subgroup analyses. This study is registered with PROSPERO, CRD42020198786. Findings: Our database search identified 11 973 records, and we included 78 eligible studies in our analyses, encompassing 63 125 individuals with dementia and 152 353 controls. Individuals with any type of dementia had a higher mortality rate than individuals without dementia (HR 5·90, 95% CI 3·53 to 9·86), and the HR for all-cause mortality was highest for Lewy body dementia (17·88, 5·87 to 54·46). After diagnosis, the mean survival time for people with Alzheimer's disease was 5·8 years (SD 2·0). Compared with people with Alzheimer's disease, a diagnosis of any non-Alzheimer's disease dementia was associated with a higher risk of all-cause mortality (HR 1·33, 1·21 to 1·46), a shorter survival time from diagnosis (MD −1·12 years, 95% CI −1·52 to −0·72), and a younger age at death (−1·76 years, −2·66 to −0·85). Survival time from disease onset was also shorter in people with non-Alzheimer's dementia, across types, compared with people with Alzheimer's disease, but the subgroup analysis revealed that this difference was only significant for vascular dementia (MD −1·27 years, −1·90 to −0·65) and dementia with Lewy bodies (MD −1·06 years, −1·68 to −0·44). The interactions between age and several survival-related outcomes were significant. 39 (50%) of the 78 included studies were rated as good quality, and large heterogeneity (I²>75%) was observed for most of the study outcomes. Interpretation: Alzheimer's disease is the most common type of dementia and one of the major causes of mortality worldwide. However, the findings from the current study suggest that non-Alzheimer's disease dementias were associated with higher morality rates and shorter life expectancy than Alzheimer's disease. Developing tailored treatment and rehabilitation programmes for different types of dementia is important for mental health providers, patients, and their families. Funding: None.