2.2. Study Population

Participants in this study were recruited from the Follow-up Cohort Study of Hypertension (FCSH), which was established in 2010 in Jiangsu Province of China. In FCSH, over 12,000 patients with hypertension from 5 different counties (Jianye district in Nanjng, Peixian county in Xizhou, Haian county in Nantong, Lianshui county in Huaian, and Sihong county in Suqian) of Jiangsu Province were involved. Eligible criteria for inclusion were as follows: adults (18-70 years), the essential hypertension (with the systolic blood pressure (SBP) ≥ 140 mmHg and/or diastolic blood pressure (DBP) ≥ 90 mmHg), and blood pressure does not reach the control target (i.e., SBP ≥ 140 or DBP ≥ 90 mmHg). Patients were excluded if they met one of the following conditions: with secondary hypertension, having comorbidities (peripheral vascular diseases, coronary artery diseases, autoimmune diseases, systemic inflammatory diseases, blood diseases, malignant tumors, acute myocardial infarction, and stroke) in the previous 3 months of the study, or with life expectancy of less than one year. All participants were followed up once a year. At each follow-up visit, blood pressure and body weight were measured and information about lifestyle (e.g., smoking, drinking, and physical activity) and diseases (e.g., cardiocerebrovascular disease, cancers, and diabetes) was updated.

By the end of 2014, there were 301 person-times cases with stroke with confirmed diagnosis. The cumulative incidence of stroke was 2.51%, and the average follow-up time was 43.4 (±10.2) months. All patients with stroke were identified by at least two neurology specialists according to clinical signs and symptoms and/or imaging data. Among the 301 cases with stroke, 90 were excluded because of recurrent stroke (N = 38), no gene polymorphism test (N = 19), no qualified blood sample (N = 9), and having other severe diseases (such as cancer, severe emphysema, and severe liver and kidney function) (N = 24). We finally included 211 cases with stroke in this study.

The control group was composed of followed-up hypertensive patients who did not have stroke, deep vein thrombosis, or myocardial infarction. Cases and controls were matched on age (±3 years old), gender, baseline blood pressure (±5 mmHg), and residential area according to the ratio of 1 : 3. At last, 633 controls were included in this study.