Each study fit an additive genetic model with a 1-degree of freedom trend test relating genotype dosage, 0 to 2 copies of the minor allele, to having or not at least 1 MRI-infarct. We used logistic regression models to calculate odds ratios (OR) with corresponding 95% confidence intervals (CI). Initial analyses were adjusted only for age and sex to avoid adjusting for covariates that might lie along a causal pathway. In addition, ARIC and CHS also adjusted for study site, and FHS adjusted for familial structure. To explore potential mechanisms, we additionally adjusted our most significant association in one model for systolic blood pressure and in another model for the presence or absence of hypertension, defined as systolic blood pressure ≥140 mm Hg, diastolic blood pressure ≥90 mm Hg or use of antihypertensive medications.17 All studies screened for latent population substructure, which was negligible (Appendix, Section 4).
