2.1 Study participants
The Kailuan Study was a prospective study conducted in the Kailuan Community of Tangshan, China. The detailed study design and procedures had been described in previous studies [13, 14]. Between June 2006 and October 2007, a total of 101,510 employees (81,110 males and 20,400 females) of the Kailuan Group were invited and agreed to participate in the Kailuan Study. Participants were followed up every 2 years. In this study, a total of 101,510 active and retired employees of Kailan Group who participated in physical examination in 2006 were included. Participants with previous history of malignant tumor (N=377), participants with previous history of HF (N=81), and participants with major data missing of MAFLD (N=2367) were excluded. Finally, a total of 98,685 volunteers were enrolled.
2.2 Data Collection
Information on demographic variables (e.g., history of use of antihypertensive, antiglycaemic or antilipidemic drugs) was collected through questionnaires; the design of epidemiological questionnaires and anthropometric methods were described in the published literature of this group [15]. After 5 minutes of rest in a chair, volunteers measured blood pressure in the left arm using the appropriate cuff size, averaging at least two readings of each systolic and diastolic blood pressure for further analysis. In addition, after 8 hours of fasting, 5ml of elbow venous blood was drawn from the morning of the physical examination day for the detection of high density lipoprotein cholesterol (HDL-C), fasting blood glucose (FPG), triglycerides and high sensitive C-reactive protein (Hs-CRP), all of which were performed on Hitachi automated analyzers. Body mass index (BMI)=body mass (kg) / height ²(m²). Diabetes was defined as FPG ≥ 7.0 mmol/L, or self-reported use of antiglycaemic drugs, history of diabetes.
2.3 Ascertainment of MAFLD
MAFLD was determined according to the recent consensus criteria [9]:MAFLD was defined as liver steatosis detected by ultrasonography in combination with one of the following three criteria:overweight/obesity (BMI≥23.0 kg/m2), presence of type 2 diabetes, or evidence of metabolic dysregulation. In our study, metabolic dysregulation among thin/normal (BMI<23.0 kg/m2) weight individuals with liver steatosis and who did not suffer from type 2 diabetes was determined by the presence of at least two of the following metabolic risk abnormalities:
1) Waist circumference ≥ 90 cm in men and 80 cm in women;
2)Blood pressure ≥ 130/85 mmHg or specific drug treatment;
3)TG ≥ 1.70 mmol/L or specific drug treatment;
4) HDL-C<1.0 mmol/L for men and <1.3 mmol/L for women, or specific drug treatment;
5) Prediabetes (FPG levels of 5.6 to 6.9 mmol/L);
6) Plasma high-sensitivity C-reactive protein level >2 mg/L; homeostasis model assessment-insulin resistance score was unavailable in our study.
The severity of steatosis was differentiated by ultrasonography: mild (diffuse increase in fine echoes in liver parenchyma), moderate (diffuse increase in fine echoes with impaired visualization of the intrahepatic vessel borders and diaphragm), and severe (diffuse increase in fine echoes with non-visualization of the intrahepatic vessel borders and diaphragm)[16]. Abdominal ultrasonography was routinely performed by experienced radiologists using a high-resolution B-mode topographical ultrasound system with a 3.5 MHz probe (ACUSON X300, Siemens, Germany) in the Kailuan study.
2.4 Follow-up and assessment of incident HF
Starting with the 2006 physical examination and last follow-up on December 31, 2020, the outcome event of the study was the first occurrence of HF. The Municipal Social Insurance Institution database and Hospital Discharge Register were linked to identify the incidence of HF based on The International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) (I50.9 for HF). HF was reviewed and recorded annually by medical staff, and all diagnoses were confirmed by professional physicians based on inpatient records. According to the criteria of the European Society of Cardiology [17], HF was defined by clinical symptoms, chest X-ray, echocardiogram and electrocardiogram.
2.5 Statistical Analyses
All analyses were performed using SAS, version 9.4 (SAS Institute, Inc, Cary, NC). Two-sided values of P<0.05 were regarded as significant. Continuous variables with normal distribution were expressed as means ± SDs and compared using Student T test , while those with skewed distribution were expressed as medians and interquartile range and compared by Kruskal-Wallis test. Categorical variables were shown in proportions and compared by Pearson’s Chi-Square test. The Cox regression model was used to predict the risk of HF in MAFLD and its metabolic disorder types, and the degree of fatty liver degeneration. The cumulative incidence of HF in different groups was calculated by the Kaplan-Meier method, and the Log-rank test was used for comparison between groups. With HF as the dependent variable and MAFLD as the independent variable, stratified analysis by age. To verify the robustness of the results, we repeated the primary analysis, excluding participants who developed myocardial infarction during follow-up for sensitivity analyses. The model was adjusted for age, sex, education level, smoking, alcohol consumption, physical activity, use of antihypertensive drugs, use of antiglycemic medications, and use of antilipidemic medications.