Cognition and mortality in older people: the Sydney Memory and Ageing Study.
BACKGROUND
Both cognitive ability and cognitive decline have been shown to predict mortality in older people. As dementia, a major form of cognitive decline, has an established association with shorter survival, it is unclear the extent to which cognitive ability and cognitive decline predict mortality in the absence of dementia.


OBJECTIVE
To determine whether cognitive ability and decline in cognitive ability predict mortality in older individuals without dementia.


METHODS
The Sydney Memory and Ageing Study is an observational population-based cohort study. Participants completed detailed neuropsychological assessments and medical examinations to assess for risk factors such as depression, obesity, hypertension, diabetes, hypercholesterolaemia, smoking and physical activity. Participants were regularly assessed at 2-year intervals over 8 years.


METHODS
A community sample in Sydney, Australia.


METHODS
One thousand and thirty-seven elderly people without dementia.


RESULTS
Overall, 236 (22.8%) participants died within 8 years. Both cognitive ability at baseline and decline in cognitive ability over 2 years predicted mortality. Decline in cognitive ability, but not baseline cognitive ability, was a significant predictor of mortality when depression and other medical risk factors were controlled for. These relationships also held when excluding incident cases of dementia.


CONCLUSIONS
The findings indicate that decline in cognition is a robust predictor of mortality in older people without dementia at a population level. This relationship is not accounted for by co-morbid depression or other established biomedical risk factors.
Dementia Collaborative Research Centre-Assessment and Better Care, UNSW Australia Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales.
Michael H
MH
Connors
Dementia Collaborative Research Centre-Assessment and Better Care, UNSW Australia Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales Neuropsychiatric Institute, Prince of Wales Hospital.
Perminder S
PS
Sachdev
Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales Neuropsychiatric Institute, Prince of Wales Hospital.
Nicole A
NA
Kochan
Dementia Collaborative Research Centre-Assessment and Better Care, UNSW Australia Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales.
Jing
J
Xu
Dementia Collaborative Research Centre-Assessment and Better Care, UNSW Australia Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales Academic Department for Old Age Psychiatry, Prince of Wales Hospital.
Brian
B
Draper
Dementia Collaborative Research Centre-Assessment and Better Care, UNSW Australia Centre for Healthy Brain Ageing (CHeBA), School of Psychiatry, University of New South Wales Academic Department for Old Age Psychiatry, Prince of Wales Hospital.
Henry
H
Brodaty
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging; D003071:Cognition; D003072:Cognition Disorders / Q000453:epidemiology / Q000401:mortality*; D015897:Comorbidity; D003704:Dementia / Q000401:mortality; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008568:Memory; D009483:Neuropsychological Tests; D009517:New South Wales / Q000453:epidemiology; D016016:Proportional Hazards Models; D012307:Risk Factors
cognition; cognitive impairment; dementia; mortality; older people