Cognitive functioning in older twins: the Older Australian Twins Study

Area of Science:

• Gerontology
• Twin Studies
• Neuroscience

Background:

• Understanding the genetic and environmental influences on cognitive aging is crucial for public health.
• Twin studies provide a powerful design to disentangle heritability from environmental factors.

Purpose of the Study:

• To investigate the concordance rates of common medical conditions and neurocognitive performance in older monozygotic (MZ) and dizygotic (DZ) twins.
• To assess the heritability of various cognitive functions and neurocognitive disorders in an aging population.

Main Methods:

• Recruitment of twins aged 65 years and older from the Australian Twin Registry.
• Comprehensive neuropsychological and medical assessments of 113 MZ and 96 DZ twin pairs.

Main Results:

• Higher concordance for hypertension and asthma observed in MZ twins compared to DZ twins.
• MZ twins showed stronger correlations than DZ twins across most cognitive tests, except for processing speed.
• Concordance for mild cognitive impairment or dementia was 76.2% in MZ twins and 42.9% in DZ twins (non-significant difference).

Conclusions:

• Most cognitive functions in older individuals exhibit significant heritability, with processing speed being a notable exception.
• The heritability of neurocognitive disorders, such as mild cognitive impairment or dementia, appears to be low in this cohort.