2.2. Data Collection

Baseline information, including demographic characteristics (age, gender, nationality, education level, residence, and marital status), lifestyle (smoking status, alcohol use, and physical activity), and chronic diseases (hypertension, dyslipidemia, diabetes mellitus, and cardiovascular diseases) was collected by trained investigators using a structured questionnaire via face-to-face interview. The questionnaire was designed by the Chinese Center for Disease Control and Prevention [23] and applied in China’s chronic disease surveillance (2010) [24].

Anthropometric measurements were collected by trained health professionals with standard procedures, which have been described in detail elsewhere [22]. Height was measured to the nearest 0.1 cm without shoes using a standard stadiometer (TZG, SHKODAK MEDICAL, Wuxi, China). Weight was measured in subjects wearing light clothing to the nearest 0.1 kg using a calibrated digital scale (TC-200K, G & G, Shanghai, China). WC was measured to the nearest 0.1 cm at the midpoint between the lowest rib margin and the level of the anterior superior iliac crest by a flexible anthropometric tape (Torch shaped waist measure, CN). BMI was calculated as weight in kg divided by height in m squared and was divided into four groups: underweight (<18.5 kg/m²), normal weight (18.5–23.9 kg/m²), overweight (24–27.9 kg/m²), and obesity (≥28 kg/m²) [25]. WHtR was calculated as WC in cm divided by height in cm. General obesity was defined as a BMI ≥ 28 kg/m² [26]. Abdominal obesity was determined if meeting one of the following criteria: (a) WC ≥ 90 cm for men, and ≥85 cm for women [11]; (b) WHtR ≥ 0.5 [27]. Change in BMI or WHtR was calculated as differences between BMI or WHtR at follow-up and the corresponding values at baseline. WHtR change was divided into five groups (no gain or gain of <0.02, gain of ≥0.02 to gain of <0.06, gain of ≥0.06 to gain of <0.12, gain of ≥0.12 to gain of <0.20, and gain of ≥0.20) and was represented by <0.02, [0.02, 0.06), [0.06, 0.12), [0.12, 0.20), and ≥0.20, respectively. BMI change was also divided into five groups (loss of >2 kg/m², loss of ≤2 kg/m² to gain of <2 kg/m², gain of ≥2 kg/m² to gain of <6 kg/m², gain of ≥6 kg/m² to gain of <12 kg/m², and gain of ≥12 kg/m²) and was represented by <−2, [−2, 2), [2, 6), [6, 12), and ≥12, respectively.

Three consecutive blood pressure measurements were taken and the mean value of three readings was used. For each participant, blood pressure measurement was performed on the right upper arm after 5 min of rest, with the participant in a seated position, using an electronic sphygmomanometer (HBP-1300, OMRON, Liaoning, China). Venous blood samples were obtained after at least 8 h overnight fasting. Plasma glucose was detected by the hexokinase method within 4 h. After centrifugation, serums separated from the remaining blood samples were stored at −20 °C and transferred to Guizhou Center for Disease Control and Prevention to detect the levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG). All samples were analyzed with an autoanalyzer (Olympus 400 analyzer, Beckman Coulter, CA, USA).

All 9280 participants were followed up for the aforementioned information and vital status by a repeated investigation during 2016–2020, and 1117 (12.04%) were lost to follow-up. All deaths were confirmed through the Death Registration Information System and Basic Public Health Service System.