medwireNews: A systematic review and meta-analysis published in The BMJ has found that the average life expectancy after a dementia diagnosis ranges from 4.5 to 8.0 years in women and from 2.2 to 5.7 years in men, depending on age.
Survival was inversely associated with age and was longer among people with Alzheimer’s disease, compared with other dementia types, and in Asian populations versus European, the investigators report.
Frank Wolters, from Erasmus MC University Medical Centre in Rotterdam, the Netherlands, and colleagues conducted a comprehensive analysis of data from 261 studies published between 1984 and 2024. The studies, with a median of 524 dementia patients each (at least 150), predominantly originated from Europe (55%), followed by North America (27%) and Asia (13%), and included over 5 million individuals with dementia (median age 79 years, 63% women). The research tracked survival outcomes in 5,553,960 participants and time to nursing home admission in 352,990 participants, with an average maximum follow-up of 7 years.
Median survival was 4.8 years from incident diagnosis of dementia onwards, equating to an overall 5-year survival probability of 51% that varied according to time from diagnosis, from 90% at 1 year to 21% at 10 years.
The researchers report that median survival decreased by a significant 1.4 years with every 10-year increase in age and was “slightly longer” in women versus men. Specifically, average life expectancy from diagnosis ranged from 8.9 years in women diagnosed at an average age of 60 years to 4.5 years in those aged an average of 85 years, and in men, from 6.5 to 2.2 years, respectively. The longer survival for women was largely due to their later age at diagnosis, say Wolters et al.
The findings suggest that “dementia shortens life expectancy by about two years for people diagnosed at age 85, 3–4 years with a diagnosis at age 80, and up to 13 years with a diagnosis at age 65,” they highlight.
Other factors significantly affecting median survival in meta-regression analysis included being from Asia compared with Europe, which was associated with a 1.2-year increase in survival, although the authors note that the regional differences “are uncertain and require further study.”
Similarly, survival was 1.4 years longer for individuals with Alzheimer’s disease compared with all-cause dementia, which is “consistent with previous studies and might result from accelerated disease progression, later diagnosis or more comorbidity,” they explain. The analysis also revealed longer survival in clinic-based studies than community-based studies (5.9 vs 4.6 years), largely due to the inclusion of younger patients in clinical settings.
Several patient characteristics identified in subanalyses were found to influence survival times, namely education, with each additional year of education shortening median survival by a significant 0.2 years, according to the outcomes of 36 studies, while cohabitation versus living alone increased median lifespan by a significant 6.22 years, based on findings from 40 studies.
The authors emphasize that differences in reported clinical characteristics and study methodologies accounted for 51% of the variation in median survival outcomes.
The median time to nursing home admission after dementia diagnosis was 3.3 years, consistent across sexes and dementia types. The probability of entering a nursing home within 1 year of diagnosis was 13%, rising to 35% within 3 years and 57% within 5 years, with older age at diagnosis associated with a significantly shorter time to nursing home placement.
In a related editorial, Bjørn Strand (Norwegian Institute of Public Health, Oslo) and Anette Ranhoff (Diakonhjemmet Hospital, Oslo, Norway) say that “[t]his is disheartening information to share with patients, and we believe these results may overestimate the risk of nursing home admission.”
They point out that “[o]nly 9% of the studies in nursing homes accounted for competing [mortality] risk, so these estimates should be interpreted with caution.”
The researchers conclude: “This systematic review found that prognosis after a dementia diagnosis is highly dependent on patient, disease, and study characteristics, offering potential for individualised prognostic information and care planning.
“Future studies on individualised prognosis should ideally include patients at time of diagnosis, accounting for personal factors, social factors, disease stage and comorbidity, while assessing relevant functional outcome measures above and beyond survival alone.”
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