APOE and Cognitive impairment: We did not detail: 1) findings in subgroups stratified by key characteristics (e.g. age, sex, ethnicity, or apolipoprotein E status); 2) how differences in the classification of mild cognitive impairment or dementia between studies may have affected the results; and 3) exclusion criteria used in different studies (e.g. in some, but not all, studies individuals with eye diseases such as glaucoma and diabetic retinopathy were excluded).