Figure 1

The probability of cognitive impairment according to education level, with the covariates fixed at their means. 0 is no education. 1 is some primary education. 2 is some secondary education or more. Sample size was 16,505 in the main analysis and cognitive impairment was defined as the lowest tertile of the shorter version of the mini-mental state examination. Sample size was 20,174 in the sensitivity analysis and cognitive impairment was defined as a score of 12 or less out of 19.