A third hypothesis suggests that diagnostic bias may play a role, because more highly schooled patients may score higher on dementia screening tests looking at cognitive ability, the authors noted.
The investigators looked at data on those who took part in the Cardiovascular Risk Factors, Aging and Dementia (CAIDE) study.
Participants of the CAIDE study came from two towns in eastern Finland. They were chosen at random from population-based samples studied in a survey starting in 1972, with follow-up every five years. In the current study, the authors examined information on 1,449 men and women ranging in age from 65 to 79 who participated in a re-examination in 1998.
They found that compared with people with only five or fewer years of formal education, those who had six to eight years of schooling had an odds ratio for dementia of 0.57 (95% confidence interval 0.29 to 1.13), whereas those with nine years of education or more had an odds ratio of 0.16 (95% CI 0.06 to 0.41).