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Mental health
Greater cognitive decline relative to normal ageing occurs at least 10 years prior to clinical dementia diagnosis
  1. Moyra E Mortby1,2,
  2. Ruth Peters2
  1. 1 School of Psychology, University of New South Wales, Sydney, New South Wales, Australia
  2. 2 Neuroscience Research Australia, Randwick, New South Wales, Australia
  1. Correspondence to Dr Moyra E Mortby, Neuroscience Research Australia, Randwick, NSW 2031, Australia; m.mortby{at}

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Commentary on: Li G, Larson EB, Shofer JB, et al. Cognitive trajectory changes over 20 years before dementia diagnosis: a large cohort study. J Am Geriatr Soc 2017;65:2627–33.


Longitudinal studies have repeatedly shown an increase in cognitive decline many years before clinical diagnosis of dementia. This decline is cited to accelerate closer to the time of diagnosis. Reported estimates of the timing of the trajectory change point (ie, the acceleration of decline) vary significantly between studies depending on the population and measure of cognition used. Further, there are inconsistencies in reported effects of education, apolipoprotein (APOE) ε4 alleles and sex on cognitive trajectories in preclinical stages. This longitudinal study aimed to estimate whether there were changes in cognitive function trajectories before dementia diagnosis and, if so, when changes occurred.1


Using data from the Adult Changes in Thought (ACT) study, a longitudinal cohort study1 of a US population with ongoing enrolment and biannual visits, Li and …

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  • Funding MEM is supported by the Australian National Health and Medical Research Council (NHMRC) and Australian Research Council (ARC) Dementia Research Development Fellowship #1102028.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; internally peer reviewed.