The average life expectancy of people diagnosed with dementia ranges from 9 years at age 60 to 4.5 years at age 85 for women and from 6.5 to just over 2 years, respectively, in men, finds a systematic review of the latest evidence in The BMJ today.
The results also suggest that one third of people with dementia are admitted to a nursing home within three years of diagnosis.
Nearly 10 million people worldwide receive a diagnosis of dementia every year, but survival estimates vary widely, and few studies have assessed prognosis (the likely course of the condition) in terms of time to nursing home admission.
To better understand this, researchers in the Netherlands set out to determine prognosis for people with a dementia diagnosis, both for remaining life expectancy and for time to nursing home admission.
Their findings are based on 261 studies published between 1984 and 2024 (235 on survival and 79 on nursing home admission) involving more than 5 million people with dementia (average age 79, 63% women).
The studies were mainly from Europe and North America with an average follow-up time of 7 years.
After assessing study quality, the researchers found that average survival from diagnosis appeared to be strongly dependent on age, ranging from 8.9 years at mean age 60 for women to 2.2 years at mean age 85 for men.
Overall, dementia reduced life expectancy by about two years for people with a diagnosis at age 85, 3-4 years with a diagnosis at age 80, and up to 13 years with a diagnosis at age 65.
Average survival was up to 1.4 years longer among Asian populations and 1.4 years longer among people with Alzheimer's disease compared with other types of dementia.
Average time to nursing home admission was just over 3 years, with 13% of people admitted in the first year after diagnosis, increasing to a third (35%) at three years and more than half (57%) at five years. However, the authors note that these estimates are less reliable and should be interpreted with caution.
These are observational findings and the authors acknowledge that differences in study methods and inconsistent reporting of measures such as socioeconomic status, race, disease severity, and pre-existing conditions may have affected their estimates.
However, they point out that the meticulous search and data extraction enabled analyses of the largest number of studies to date over a prolonged period, "offering potential for individualised prognostic information and care planning."
They conclude: "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."
In a linked editorial, researchers from Norway say although the understanding of survival with dementia has advanced substantially, the complexities of predicting the timeline for nursing home admission persist
"To enhance future healthcare services and optimise quality of life for people with dementia and their families, it is crucial that we continue to strive for more precise, context sensitive insights," they conclude.
