eTable 1. Definition of demographic and clinical characteristics.
| Characteristic | Missing | Definition | |
| General characteristics | Age group | 0.0% | Age range 30–95 years: 30–39, 40–49, 50–59, 60–69, ≥ 70 years |
| Sex | 0.0% | Women, men | |
| Education | 1.0% | Based on the International Standard Classification of Education 2011 (ISCED): low (lower secondary education or below), middle (upper secondary education to undergraduate university level), high (postgraduate university study) | |
| Smoking | 5.9% | Persons who have never smoked, formerly smoked, or currently smoke | |
| Body mass index | 0.4% | Body mass divided by square of body height (kg/m2) | |
| Comorbidities | Diabetes | 0.9% | Self-reported physician diagnosis and/or glycated hemoglobin (HbA1c) (no diabetes < 6.5%; diabetes ≥ 6.5%), fasting glucose (no diabetes < 126 mg/dl; diabetes ≥ 126 mg/dl) measured in fasting morning blood, and/or intake of antidiabetics |
| Hypertension | 1.6% | Based on the 2018 European Society of Cardiology guidelines for the management of arterial hypertension: mean systolic blood pressure ≥ 140 mmHg and/or mean diastolic blood pressure ≥ 90 mmHg and/or antihypertensive drug use, irrespective of blood pressure | |
| Cardiovascular disease | 0.4% | Based on a self-reported physician diagnosis of one or more of the following conditions: myocardial infarction, coronary artery disease, cardiac insufficiency, cardiac pacemaker, peripheral artery occlusive disease, stroke, surgery on large vessels such as aorta, carotid, or peripheral vessels | |
| Chronic kidney disease | 5.5% | Estimated glomerular filtration rate based on cystatin C (no CKD ≥ 60 mL/min/1.73 m2; CKD < 60 ml/min/1.73 m2) | |
| Medication | LT4 dosage (µg/kg/d) | 0.4% | Daily dose of LT4 consumed, expressed in relation to body weight |
| LT4 intake duration | 0.0% | 0–12 months, 13–36 months, > 36 months | |
| Iodine supplementation | 0.4% | Regular intake of iodine (ATC H03CA01) | |
| Polypharmacy | 0.0% | Regular use of ≥ 5 prescribed drugs | |
| Cognition | Global cognition (z-standardized) | 1.9% | Derived from a cognitive test battery assessing episodic verbal memory, working memory, executive function and processing speed |
CKD, Chronic kidney disease; LT4, levothyroxine