Significant variations in survival times of early onset dementia by clinical subtype

The survival rates of people with early onset dementia—diagnosed before the age of 65—vary considerably by clinical type, but sex, age, family history and co-existing conditions aren't specific risk factors, finds research published online in the Journal of Neurology Neurosurgery & Psychiatry.

Although the survival of those afflicted by dementia in older age is shorter, the overall impact on the risk of death from any cause is even greater in those with early onset disease than it is in others of comparable age, say the researchers. 

Around 5% of dementia cases globally are categorised as early onset. But while dementia is widely recognised as a life-limiting condition among elderly people, few studies have assessed survival times and the factors associated with prognosis in those with early onset disease, explain the researchers.

To explore this further and help inform the treatment and care provision of those diagnosed with early onset dementia, the researchers reviewed and reassessed all 12,490 visits made to dementia outpatient clinics in two university hospital districts in Finland between 2010 and 2021.

Some 794 confirmed cases of early onset dementia were identified, to include Alzheimer’s disease, frontotemporal dementia, alpha-synucleinopathies (in particular, Lewy body dementia), and ‘other’ and ‘mixed’ dementia, which included vascular cognitive impairment. 

The survival times of each of these cases was compared with those of 10 people without neurodegenerative disease, but matched for age, sex, and geographical region, from general population data registers (7930 people in total).

During the study period, 215 people with early onset dementia died. Their average survival time was nearly 9 years, but varied according to disease subtype.

The shortest survival time of nearly 7 years was seen among those with frontotemporal dementia or Lewy body dementia (7 years), although those with both frontotemporal dementia and motor neurone disease (ALS) lived for just over 2 years, on average. 

Those with Alzheimer’s disease lived for nearly 10 years, on average, while those with vascular cognitive impairment lived the longest—over 10 years, on average.

Compared with those without neurodegenerative disease, the death rate from any cause among those with early onset dementia was more than 6.5 times higher. But when categorised by disease subtype, it was nearly 14 times as high in those with frontotemporal dementia, and more than 4 times as high among those with vascular cognitive impairment, for example.

Male sex, older age, several co-existing conditions, and lower educational attainment were all universally associated with an increased risk of death, but they weren’t specific to early onset dementia. It was the diagnosis of early onset dementia itself that was most strongly and independently associated with survival time, say the researchers.

Only diabetes, which is a known risk factor for dementia, was associated with shorter survival time among those with early onset dementia.

“Overall, although the survival time in years appears shorter in older patients, the impact of dementia diagnosis on all-cause mortality is more significant in the [early onset dementia] age group than in the late onset patients when compared with the general population,” comment the researchers.

This is an observational study, and no definitive conclusions can be drawn about cause and effect. The researchers also acknowledge various limitations to their findings, including that most of the study participants had no genetic or neuropathological confirmation of their dementia. And the numbers in each clinical subgroup were small.

“Our study provides up-to-date [early onset dementia] survival rates in a validated population-based [early onset dementia] cohort, and highlights the substantial effect caused by [its] diagnosis on patients’ mortality,” conclude the researchers.

“Accurate up-to-date data on the survival and mortality rates of [early onset dementia] are crucial in designing healthcare structures, comprehensive patient care, and clinical trials,” they add.