['To examine the association of alcohol consumption over 10 years with cognitive performance in different socio-economic groups.', 'Prospective cohort study, the French GAZEL study.', 'France.', "Employees of France's national electricity and gas company.", 'Alcohol intake was assessed annually, beginning in 1992, using questions on frequency and quantity of alcoholic beverages consumed in a week; used to define mean consumption and trajectory of alcohol intake over 10 years. Cognitive performance among participants aged ≥\u200355 years (n = 4073) was assessed in 2002-04 using the Digit Symbol Substitution Test (DSST), a measure of psychomotor speed, attention and reasoning. Occupational position at age 35 and education were used as the markers of socio-economic position.', 'All analyses were stratified by socio-economic position. In the low occupational group, participants consuming a mean of more than 21 drinks per week had 2.1 points lower (95% CI: -3.9, -0.3) DSST score compared to those consuming four to 14 drinks per week. In participants with primary school education, the corresponding difference was 3.6 points (95% CI: -7.1, -0.0). No association between alcohol consumption and cognitive performance was observed in the intermediate and high socio-economic groups, defined using either occupation or education. Analysis of trajectories of alcohol consumption showed that in the low socio-economic groups large increase or decrease in alcohol consumption was associated with lower cognitive scores compared to stable consumption.'] Is high alcohol consumption in middle-aged adults associated with poorer cognitive performance only in the low socio-economic group . Results from the GAZEL cohort study?