Study population
The study participants were consecutively recruited from a population-based, cross-sectional study in the health center of Ruijin Hospital, Luwan branch, Huangpu district, Shanghai. First, from March to August 2020, individuals aged 40 years or older who were natives of Shanghai municipality or those who had lived in Shanghai for at least 5 years who underwent health checks in this health center were enrolled. Second, we invited participants to participate in the study by telephone. Participants were excluded if they met one of the following criteria: unable to consent; pregnancy; or critical illness such as cancer, organ transplant or dialysis treatments. At this stage, 10824 participants were called. Third, 9214 participants provided informed consent and were recruited (response rate 85.1%). The exclusion criteria were as follows: missing blood pressure data (n = 2); missing triglyceride levels (n = 122); and missing waist circumference (n = 75). Finally, 9015 subjects were included in the analysis. (Fig. 1)。
The study protocol (No. LWEC2020024) was approved by the Ethics Committee of the Shanghai Ruijin Hospital, Luwan branch, Shanghai Jiao Tong University School of Medicine. Informed consent was obtained from all participants included in our study. We confirmed that all methods were performed in accordance with the relevant guidelines and regulations.
Clinical, Anthropometric And Laboratory Measurements
An experienced personnel finished all interviews including the questionnaire covering sociodemographic characteristics, medical history, family history and lifestyle factors. Body mass index (BMI) was calculated as weight (in kilograms) divided by height (in meters squared). BMI < 24 kg/m2 was defined as normal weight, while BMI ≥ 24 kg/m2 was defined as overweight/obese, as determined by the Cooperative Meta-Analysis Group of the Working Group on Obesity in China criteria[18]. Blood pressure (BP) was measured by a trained physician with an electronic sphygmomanometer (Omron HEM-7200 Monitor, Batteries, and Stopwatch). The blood pressure was measured 3 times at 5-minute intervals after the participants in this study were required to rest in a seated position for at least 5 minutes. The mean of the 3 readings was calculated. Waist circumference (WC) was measured 1 cm above the umbilicus. Drinking and smoking status were divided into never drinking/smoking and past or current drinking/smoking. Educational level was categorized as whether below high school or not. Physical activity included occupational and leisure-time physical activity, which were merged and regrouped into the self-reported high level of both occupational and leisure-time physical activity or below[19].
Blood samples were obtained after fasting for at least 8 h. Serum samples were aliquoted and frozen at a central laboratory. Glycated hemoglobin (HbA1c) was measured by a high-performance liquid chromatography (MQ-2000PT) (HPLC) automatic HbA1c analyzer (MEDCONN, Huizhong Medical Science and Technology Co., Ltd, Shanghai, China; Shanghai Huachen Biological Reagent Co., Ltd, Shanghai, China). Alutamic oxaloacetic transaminase (AST), Glutamic pyruvic transaminase (ALT), fasting plasma glucose (FPG), total cholesterol (TC), high-density lipoprotein (HDL-C) and low-density lipoprotein cholesterol (LDL-C) were also measured (AU680 Chemistry Analyzer, Beckman Coulter, Brea, CA, USA). TG was measured with assay kits from Beckman Coulter (catalog number: AUZ5612, assay sensitivity: 0.01 mmol/L, intra-assay variability: 6.25%), as was FPG (catalog number: AUZ4686, assay sensitivity: 0.04 mmol/L, intra-assay variability: 2.5%). Serum UA was analysed with a Beckman Coulter AU 680 device with the original kit (Brea, California, USA). The validity and accuracy of UA were 6% and 4%, respectively. The eGFR was determined using the Chinese modified Chronic Kidney Disease Epidemiology Collaboration[20].
Definition Of Variables
Hypertension was diagnosed as systolic blood pressure ≥ 140 mmHg, diastolic blood pressure ≥ 90 mmHg, or a self-reported previous physician’s diagnosis of hypertension. HUA was defined as serum UA > 420 µmol/L for men and > 360 µmol/L for women[21].
Definitions Of Htgw And The Rest Of The Phenotypes
Participants were grouped into four phenotype groups according to the measurements of TG and WC: (1) Normal waist circumference and normal triglycerides (NWNT): TG ≤ 1.7 mmol/L, WC < 90 cm for men and WC < 80 cm for women; (2)Normal waist circumference and elevated triglycerides (NWET):TG > 1.7 mmol/L, WC < 90 cm for men and WC < 80 cm for women; (3) Elevated waist circumference and normal triglycerides (EWNT ):TG ≤ 1.7 mmol/L, WC ≥ 90 cm for men and ≥ 80 cm for women;(4) Hypertriglyceridemic waist (HTGW):TG > 1.7 mmol/L, WC ≥ 90 cm for men and ≥ 80 cm for women[22].
Statistical Analyses
Data analyses were performed using IBM SPSS version 25 statistical software (IBM Corp., Armonk, NY, USA). P < 0.05 indicated significance (two-sided). Continuous variables are presented as mean ± standard deviation (SD), and categorical variables are presented as percentages (%) as appropriate. Pearson’s correlation was used to analyze the relationship between uric acid and each potentially associated factor, including FBG, HBA1c, blood glucose, blood pressure, lipids, eGFR, WC and ALT after adjusted by sex, age, BMI. Both linear and logistic regression analysis were used to test for our phenotype groups and hyperuricaemia. Model 1 was adjusted for age, sex, BMI, current smoking and current drinking. Model 2 was adjusted for Model 1 plus TC, LDL, FBG, HbA1c, eGFR, systolic blood pressure, diastolic blood pressure, diabetes, anti-diabetes agents, hypertension, anti-hypertension drug.
For sensitivity analyses, we repeated the analyses to examine the association of triglyceride waist phenotypes with hyperuricemia. We performed stratified analyses and potential effect modifications by age (< 60 years, ≥ 60 years), BMI (< 24 kg/m2, ≥ 24 kg/m2), presence or absence of CKD, presence or absence of hypertension and presence or absence of diabetes. The same confounding factors as above were adjusted for the analyses.