From the aDivision of Psychiatry, Centre for Clinical Brain Sciences, University of Edinburgh, Edinburgh, United Kingdom; bAlzheimer Scotland Dementia Research Centre, University of Edinburgh, Edinburgh, United Kingdom; cCentre for Cognitive Ageing & Cognitive Epidemiology, University of Edinburgh, Edinburgh, United Kingdom; dCentre for Dementia Prevention, University of Edinburgh, Edinburgh, United Kingdom; eGreater Glasgow & Clyde Nursing Homes Medical Practice, NHS Greater Glasgow & Clyde, Glasgow, United Kingdom; fDepartment of Epidemiology and Public Health, University College London, London, United Kingdom; gEdinburgh Medical School, University of Edinburgh, Edinburgh, United Kingdom; and hDepartment of Psychology, University of Edinburgh, Edinburgh, United Kingdom.
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Background:The prevention of dementia is a global priority but its etiology is poorly understood. Early life cognitive ability has been linked to subsequent dementia risk but studies to date have been small and none has examined sex differences.Methods:In the 1932 Scottish Mental Survey cohort, we related intelligence test scores at age 11 years in 16,370 boys and 16,097 girls (born in 1921) to incident dementia ages ≥65 years as ascertained using probabilistic linkage to electronic health records up to the age of 92 years (1,231 cases in men, 2,163 in women; median follow-up 15 years).Results:Compared with the highest intelligence group (IQ ≥115), dementia risk was raised in the lowest-scoring category (<85) and these associations were stronger for women (hazard ratio; 95% confidence interval: 1.51; 1.29, 1.76) than men (1.19; 0.98, 1.44; P value for interaction by gender: 0.054). There was evidence of a dose–response association between childhood IQ and dementia in women (IQ 100–114.9 compared with ≥115: 1.18; 1.03, 1.34; IQ 85–99.9: 1.32; 1.15, 1.51; P value for trend <0.001) but not in men (1.05; 0.89, 1.24 and 1.01; 0.85, 1.21; 0.44).Conclusions:Childhood intelligence is related to subsequent dementia risk but this association is not the same in men and women. See video abstract at, http://links.lww.com/EDE/B184.