What cognitive changes can be expected with normal ageing?

Background: This paper briefly summarizes recent evidence on the nature of cognitive decline, the variability in individual responses to ageing, and risk factors known to affect the rate of cognitive decline. Method: Data from the Canberra Longitudinal Study were used to examine the course and diversity of cognitive decline. The sample consisted of 887 participants aged 70-93 years, who were examined in 1991 and followed up in 1994 and 1998. Data summarizing significant risk factors for cognitive decline were based on a review of 34 studies that examined the following predictors: education, the APOE ε4 allele, health, activity and blood pressure. Results: Using data from participants living in the community, there is evidence that cognitive speed and memory performance decline with age, but that crystallized abilities remain largely intact in those who survive for long-term follow-up. Variability in test scores for memory and speed increases with age. There is evidence that poor health, fewer years of education, lower activity, the presence of the APOE ε4 allele, and blood pressure predict faster cognitive decline. Conclusions: The diversity in cognitive ageing suggests that more than one process may be operating to produce the observed cognitive outcomes. Education, good health, absence of the APOE ε4 allele, and activity may be protective of cognitive decline. Preventative strategies for sustaining high intellectual performance in later life may therefore be possible. These findings also speak to the need to extend analysis beyond examining mean changes in cognitive performance to an analysis based on individual differences in change.