Dementia and mortality in older adults: A twin study, 2023, Jung Yun Jang et al

Dementia and mortality in older adults: A twin study

Highlights

• We studied dementia and mortality in twin pairs discordant for dementia.
• People without dementia outlived people with dementia.
• Identical twins with dementia and their co-twin controls had similar survival time.
• Findings suggest genotype may explain the link between dementia and mortality.

INTRODUCTION

Dementia predicts increased mortality. We used case-control and co-twin control models to investigate genetic and shared environmental influences on this association.

METHODS
Case-control design, including 987 twins with dementia and 2938 age- and sex-matched controls in the Swedish Twin Registry. Co-twin control design, including 90 monozygotic (MZ) and 288 dizygotic (DZ) twin pairs discordant for dementia. To test for genetic and environmental confounding, differences were examined in mortality risk between twins with dementia and their matched or co-twin controls.

RESULTS
Twins with dementia showed greater mortality risk than age- and sex-matched controls (HR = 2.02 [1.86, 2.18]). Mortality risk is significantly elevated but attenuated substantially in discordant twin pairs, for example, comparing MZ twins with dementia to their co-twin controls (HR = 1.48 [1.08, 2.04]).

DISCUSSION
Findings suggest that genetic factors partially confound the association between dementia and mortality and provide an alternative hypothesis to increased mortality due to dementia itself.

https://alz-journals.onlinelibrary.wiley.com/doi/10.1002/alz.13553
Covered in different news reports https://medicalxpress.com/news/2023-12-alzheimer-sibling-shortened-lifespan.html