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P4‐124: Recent findings from the Older Australian Twins Study (OATS)
Author(s) -
Sachdev Perminder,
Trollor Julian,
Lammel Andrea,
Lee Teresa,
Wright Margaret,
Ames David,
Brodaty Henry,
Wen Wei
Publication year - 2012
Publication title -
alzheimer's and dementia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.713
H-Index - 118
eISSN - 1552-5279
pISSN - 1552-5260
DOI - 10.1016/j.jalz.2012.05.1827
Subject(s) - heritability , neurocognitive , twin study , cognition , neuropsychology , cohort , psychology , neuroimaging , executive functions , neuropsychological assessment , developmental psychology , medicine , biology , psychiatry , genetics
Background: The Older Australian Twins Study (OATS) was initiated to investigate genetic and environmental factors and their associations and interactions in healthy brain ageing and ageing-related neurocognitive disorders. Methods: Twins aged 65 years and older were recruited through the Australian Twin Registry. Participants receive a comprehensive neuropsychiatric assessment at baseline and a follow up every two years, along with MRI scans, clinical chemistry, inflammatory and metabolic markers, proteomics and genomics (Illumina Express). The cohort is nearing completion of Wave 2 and Wave 3 is planned from 2013. Initial analyses relate to cognitive function and neuroimaging measures. Results: The sample size of the cohort at Wave 1 is N1⁄4551 (MZ 135 pairs, DZ 106 pairs; singletons: MZ 20, DZ 25; Sibs 24). MZ twins have higher correlations than DZ twins on most neuropsychological tests, with the exception of some speeded tests. Multivariate genetic modelling showed that additive genetic factors explained 42 to 62% of the variance in five processing speed measures. As for executive functions, heritability of the four measures was variable, between 30 to 63%. The covariation between the processing speed measures and general cognitive ability, and between executive functions measures and general cognitive ability, were both attributable to a common genetic factor. Processing Speed was found to be the stronger mediator of age and episodic memory, as well as age and fluid intelligence, than executive functions. Proton magnetic resonance spectroscopy measures (NAA, Cr, Cho, mI) showed high heritability, being highest for NAA (N-acetyl aspartate). The global sulcal index also exhibited high heritability (79%). White matter hyperintensities were highly heritable with no significant age and sex effect. Conclusions: OATS provides a unique data set to examine genetic and environmental influences in a range of ageing-related phenotypes, in particular domains of cognitive function and brain chemistry not previously examined.