Sydney Memory and Ageing Study: An epidemiological cohort study of brain ageing and dementia

Abstract

Non-demented community-dwelling older adults aged 70–90 years (n = 1,037) randomly recruited from the electoral roll completed neuropsychological and medical assessments over six years. The overall prevalence of mild cognitive impairment (MCI) at baseline was 36.7%. Risk factors for MCI include APOE ϵ4 allele carrier status, high homocysteine, heart disease, poor odour identification, low visual acuity and low mental activity, but notable age and sex differences were observed. Neuropsychiatric symptoms were rare; depression was the most common and was associated with cognitive impairment in at least one domain as well as subsequent dementia 2 years later. Poorer cognitively demanding functional abilities were associated with cognitive impairment.

Biomarkers for cognitive impairment and decline were identified. Inflammatory markers and plasma apolipoprotein levels were associated with poorer performance in the attention/processing speed domain. Measures of white matter lesions, white matter integrity, sulcal morphology and tractography were identified as novel biomarkers of early cognitive decline. Stronger deactivation in the posteromedial cortex with increasing memory load on functional MRI predicted future decline.

Compared to previous reports, our prevalence rates of MCI were higher but rates of progression to dementia and reversion to normal were similar, as were risk factors for progression to dementia.

Acknowledgements

We thank the participants for their enthusiastic support. The Sydney Memory and Ageing Study Team contributed to the study design and data acquisition, and comprises Shaily Aggarwal, Alexandra Aiken, Allison Bowman, G.A. (Tony) Broe, Kim Burns, Michele de Permentier, Joula Dekker, Louise Dooley, Sarah Fairjones, Janelle Fletcher, Therese French, Cathy Foster, Emma Nugent-Cleary-Fox, Chien Gooi, Evelyn Harvey, Rebekah Helyer, Sharpley Hsieh, Laura Hughes, Sarah Jacek, Mary Johnston, Angela King, Kate Maston, Donna McCade, Samantha Meeth, Eveline Milne, Angharad Moir, Ros O’Grady, Kia Pfaeffli, Carine Pose, Wiebke Queisser, Laura Reuser, Amanda Rose, Zeeshan Shahnawaz, Amanda Sharpley, Claire Thompson, and Sam Wong. Apolipoprotein measurements were undertaken by Fei Song in the laboratory of Anne Poljak, University of New South Wales (UNSW). DNA was extracted by Genetic Repositories Australia, and genetic work was undertaken in the laboratory of John Kwok and Peter Schofield, Neuroscience Research Australia. Collaborators at UNSW include Katherine Samaras, Lesley Campbell, Stephen Lord, Jasmine Menant, Daina Sturnieks, Kim Delbaere, Anne Poljak, Ora Lux, Lee-Fay Low and Megan Heffernan.

Declaration of interest: This study is supported by the Australian National Health and Medical Research Council (NHMRC) Program Grants 350833 and 568969. Genetic Repositories Australia is 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. Nicole Kochan is supported by an NHMRC Early Career Fellowship and NHMRC Capacity Building Grant 568940. Simone Reppermund is supported by an NHMRC Capacity Building Grant 568940. Arezoo Assareh was supported by a PhD scholarship from the Dementia Collaborative Research Centre – Assessment and Better Care at the University of New South Wales. The authors alone are responsible for the content and writing of the paper.