Education and trajectories of cognitive decline over 9 years in very old people: methods and risk analysis.
BACKGROUND
the investigation of cognitive decline in the older population has been hampered by analytical considerations. Most studies of older people over prolonged periods suffer from loss to follow-up, yet this has seldom been investigated fully to date. Such considerations limit our understanding of how basic variables such as education can affect cognitive trajectories.


METHODS
we examined cognitive trajectories in a population-based cohort study in Cambridge, UK, of people aged 75 and over in whom multiple interviews were conducted over time. Cognitive function was assessed using the Mini-Mental State Examination (MMSE). Socio-demographic variables were measured, including educational level and social class. An age-based quadratic latent growth model was fitted to cognitive scores. The effect of socio-demographic variables was examined on all latent variables and the probability of death and dropout.


RESULTS
at baseline, age, education, social class and mobility were associated with cognitive performance. Education and social class were not related to decline or its rate of change. In contrast, poor mobility was associated with lower cognitive performance, increased cognitive decline and increased rate of change of cognitive decline. Gender, age, mobility and cognitive ability predicted death and dropout


CONCLUSIONS
contrary to much of the current literature, education was not related to rate of cognitive decline or change in this rate as measured by MMSE. Higher levels of education do not appear to protect against cognitive decline, though if the MMSE is used in the diagnostic process, individuals with less education may be diagnosed as having dementia somewhat earlier.
Muniz-Terrera
Graciela
G
MRC Biostatistics Unit, Institute of Public Health, Robinson Way, University Forvie Site, Cambridge, CB2 0SR, UK. graciela.muniz@mrc-bsu.cam.ac.uk
Matthews
Fiona
F
Dening
Tom
T
Huppert
Felicia A
FA
Brayne
Carol
C
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D003072:Cognition Disorders / Q000175:diagnosis / Q000453:epidemiology* / Q000209:etiology; D018450:Disease Progression; D004522:Educational Status; D004739:England / Q000453:epidemiology; D005260:Female; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D011159:Population Surveillance; D011569:Psychiatric Status Rating Scales; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors