The contribution of twins to the study of cognitive ageing and dementia: The Older Australian Twins Study

Abstract

The Older Australian Twins Study (OATS) is a major longitudinal study of twins, aged ≥ 65 years, to investigate genetic and environmental factors and their interactions in healthy brain ageing and neurocognitive disorders. The study collects psychiatric, neuropsychological, cardiovascular, metabolic, biochemical, neuroimaging, genomic and proteomic data, with two-yearly assessments, and is currently in its third wave. The initial cohort comprises 623 individuals (161 monozygotic and 124 dizygotic twin pairs; 1 MZ triplets; 27 single twins and 23 non-twin siblings), of whom 426 have had wave 2 assessment. A number of salient findings have emerged thus far which assist in the understanding of genetic contributions to cognitive functions such as processing speed, executive ability and episodic memory, and which support the brain reserve hypothesis. The heritability of brain structures, both cortical and subcortical, brain spectroscopic metabolites and markers of small vessel disease, such as lacunar infarction and white matter hyperintensities, have been examined and can inform future genetic investigations. Work on amyloid imaging and functional magnetic resonance imaging is proceeding and epigenetic studies are progressing. This internationally important study has the potential to inform research into cognitive ageing in the future, and offers an excellent resource for collaborative work.

Acknowledgements

We thank the participants of the Older Australian Twins Study. We also thank the SEALS Laboratories of the South Eastern Sydney and Illawarra Area Health Service for blood tests, Symbion Imaging for MRI scans, and Symbion Pathology for blood collection. Sophia Dean assisted with the preparation of the manuscript.

Declaration of interest: We would like to acknowledge access to the Australian Twin Registry, which is a national research resource supported by the NHMRC Enabling Grant 310667 that is administered by the University of Melbourne. DNA was extracted by Genetic Repositories Australia, an Enabling Facility supported by the NHMRC Grant 401184. Karen Mather is supported by an Alzheimer's Australia Dementia Research Foundation Postdoctoral Fellowship and NHMRC Capacity Building Grant 568940. This study is support by an NHMRC/ARC Strategic Award Grant of the Ageing Well, Ageing Productively Program (ID No. 401162) and an NHMRC Project Grant (ID 1045325). The authors alone are responsible for the content and writing of the paper.