The aims of the study were to explore general trends and individual differences in cognitive changes from early adulthood to late midlife and to investigate associations between education and cognitive changes. We used data from the Lifestyle and Cognition Follow-Up Study 2015 on 1,543 Danish men born in 1950-1961. Test scores on the 78-item intelligence test used by the Danish conscription authorities, Børge Priens Prøve (BPP), completed at draft board examination (baseline, mean age = 20 years) and at follow-up (mean age = 61 years) were used to measure cognitive changes. The mean change in BPP scores was -2.94 (SD = 5.57), and a retest correlation of 0.81 between the baseline and follow-up BPP scores was observed. In spite of the substantial retest correlations, the 8.3% of the sample with statistically reliable change had a mean decline in BPP scores of -13.41 (SD = 2.56). In latent change score models adjusted for year of birth and retest interval, more years of education was associated with larger decline in BPP scores, but the association was reversed when further adjusting for baseline BPP scores. Moreover, significant interactions indicated that more years of education was associated with less cognitive decline in men with relatively low or average BPP scores at baseline, whereas no influence of education was found in men with high baseline scores. Hence, more years of education may compensate for low or average intelligence by increasing cognitive reserve in these individuals or by influencing mediating lifestyle and occupational factors. (PsycINFO Database Record (c) 2019 APA, all rights reserved).