Abstract
IntroductionAn aging population brings increasing burdens and costs to individuals and society arising from late-life cognitive decline, the causes of which are unclear. We aimed to identify factors predicting late-life cognitive decline.MethodsParticipants were 889 community-dwelling 70–90-year-olds from the Sydney Memory and Ageing Study with comprehensive neuropsychological assessments at baseline and a 2-year follow-up and initially without dementia. Cognitive decline was considered as incident mild cognitive impairment (MCI) or dementia, as well as decreases in attention/processing speed, executive function, memory, and global cognition. Associations with baseline demographic, lifestyle, health and medical factors were determined.ResultsAll cognitive measures showed decline and 14% of participants developed incident MCI or dementia. Across all participants, risk factors for decline included older age and poorer smelling ability most prominently, but also more education, history of depression, being male, higher homocysteine, coronary artery disease, arthritis, low health status, and stroke. Protective factors included marriage, kidney disease, and antidepressant use. For some of these factors the association varied with age or differed between men and women. Additional risk and protective factors that were strictly age- and/or sex-dependent were also identified. We found salient population attributable risks (8.7–49.5%) for older age, being male or unmarried, poor smelling ability, coronary artery disease, arthritis, stroke, and high homocysteine.DiscussionPreventing or treating conditions typically associated with aging might reduce population-wide late-life cognitive decline. Interventions tailored to particular age and sex groups may offer further benefits.
Highlights
An aging population brings increasing burdens and costs to individuals and society arising from late-life cognitive decline, the causes of which are unclear
The cognitive status of 665 participants could be classified at both baseline and follow-up, with 77 new cases of mild cognitive impairment (MCI) and 16 new cases of dementia at follow-up
While apolipoprotein E (APOE) e4 reportedly promotes a transition from MCI to AD, its association with MCI itself may be low [4]. This might explain why we found no association between APOE e4 and incident MCI/dementia, as over 80% of our incident cases were MCI
Summary
An aging population brings increasing burdens and costs to individuals and society arising from late-life cognitive decline, the causes of which are unclear. Mitigating cognitive decline requires knowing its causes, but a recent systematic review [2] found the evidence for putative risk and protective factors reported by observational studies to be inconsistent or only poorly supported This could be because associations with cognitive decline are complicated by effects that vary with age [2], sex [3,4] and cognitive measure [5,6,7,8]. A focus on effects varying with age or sex was maintained, and we again investigated a broad range of factors that included sociodemographic characteristics and lifestyle, medications, cardiac, physical, mental and general health, and biochemical indices of health This included a number of factors frequently associated with poorer cognition in the elderly, including apolipoprotein E (APOE) e4 status [2] and smelling ability [8,11,12,13]. This statistic considers prevalence in addition to strength of association, and may help identify interventions offering the greatest population-wide benefits
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