Confounding Variables

Age, sex, educational level, body weight, and geographic location were identified as the key confounding variables. Age, sex, and educational level information was collected from computerized questionnaires completed at UK Biobank assessment centers. Highest educational level and qualifications responses were dichotomized to categorize participants as either having or not having university/college degree–level qualifications. Body weight measurement was acquired by a research assistant on-site during the physical health assessments. Geographic location was determined from the UK Biobank assessment center, which was recorded automatically during data collection.