Twin's Dementia Tied to Shorter Life Expectancy in Unaffected Twin

TUESDAY, Dec. 19, 2023 (HealthDay News) -- Shared genes and environment can lead twins with dementia to a shortened life expectancy, even if only one develops dementia, according to a study published online Dec. 11 in Alzheimer’s & Dementia.

Jung Yun Jang, Ph.D., from the Institute for Memory Impairments and Neurological Disorders at the University of California Irvine, and colleagues used case-control and cotwin control models to investigate genetic and shared environmental influences on the association between dementia and mortality. The analysis included 987 twins with dementia and 2,938 age- and sex-matched controls in the Swedish Twin Registry. The cotwin control design included 90 monozygotic (MZ) and 288 dizygotic twin pairs discordant for dementia status.

The researchers found that twins with dementia showed greater mortality risk than age- and sex-matched controls (hazard ratio, 2.02). Mortality risk was elevated but attenuated substantially in discordant twin pairs (MZ twins with dementia to cotwin controls: hazard ratio, 1.48).

"We expected a different result. We expected that, in twins where one developed dementia and the other did not, the difference in lifespan would be just like we see in unrelated people," Jang said in a statement. "What we’re seeing instead is the increased risk of mortality is not due to just the dementia itself, but also a whole package of other influences that the person brings to their disease."

Abstract/Full Text