Pre-existing dementia tied to higher cancer mortality
Five-year cancer-specific mortality reached 44.0% in cancer patients with dementia compared with 39.4% in matched cancer patients without dementia.
The Lancet Healthy Longevity
In a nationwide cohort of Danish cancer patients diagnosed between 1995 and 2022, researchers matched 17,425 individuals with pre-existing dementia to 86,823 cancer patients without dementia. Matching accounted for cancer site, age, sex, and calendar period. Patients with pre-existing dementia experienced higher risks of dying over five years. Their five-year cancer-specific mortality was 44.0% compared with 39.4% among those without dementia, showing a 4.5% risk difference. All-cause mortality showed an excess risk difference of 22.2%. In multivariable-adjusted models, comorbid dementia was associated with elevated cancer-specific mortality (hazard ratio 1.28) and all-cause mortality (hazard ratio 2.03). Dementia-related excess cancer mortality was highest among patients diagnosed with colon, rectal, and breast cancers.
Why it matters
Cancer and dementia are two primary age-related conditions that increasingly co-occur as populations grow older. Understanding how neurodegenerative disease impairs cancer survival highlights the clinical challenges of managing complex multimorbidity in aging individuals.
Caveats
The findings rely on an observational registry design in Denmark, which cannot determine direct causality. The analysis also depended on recorded diagnoses in administrative health registries.
The paper
Aarhus University
The Lancet Healthy Longevity · 29 Sep 2026