Study population
In our previous paper, we described the characteristics of the study in detail [8]. From January 2001 to August 2003, we enrolled residents older than 35 years to evaluate the prevalence, morbidity rate and historical process of CVD in villages in Liaoning Province in the Northeast area of China. The exclusion criteria were previously described [12].
Pregnant subjects and those who had a mental disorder or malignant tumors and had severe psychiatric disturbances, hepatic failure, or end-stage renal failure were excluded in the present research. We asked 14,016 eligible residents from different villages who were 35 years or older to participate in our research. Of the 14,016 residents that were asked, 85.3% responded and agreed to participate and complete the research. This research was approved by the Ethics Committee of the Chinese Medical University (China Shen Yang, AF-SDP-07-1,0-01). The research procedures followed the ethically normative criteria. Participants’ welfare, medical plans and confidentiality agreements associated with their contact details were determined before the research began. Then, a written consent form was given to the participants. In this report, we used baseline data, and only participants with a complete set of data regarding the variables to be analyzed in the study were included, making the final sample size 6,837 (3,150 men and 3,687 women). In terms of the possible disorders that were responsible for left ventricular hypertrophy, 127 of the cases had renal diseases, 313 had diabetes history, and 1,451 had hypertension.
Data Collection and Measurements
Data collection
All of the data in our study were gathered by a skilled, trained cardiologist and nurses during clinical face to face interviews with a standardized questionnaire. We conducted an organized training session for all of the investigators before the study to ensure that they were qualified to participate in the interview [8, 12]. After the training session, the participants took a test to determine whether they were qualified to collect data. Further guidance and assistance were provided during the investigation. The data obtained through the interviews with the standard questionnaire included current drinking status, current smoking status, exercise status and educational level [8, 12]. The central steering committee and quality control committee were responsible for guiding this study. Exercise status was categorized into the following three levels: low, moderate and high, and the specific standard was previously described [8]. Education levels were divided into primary school or below, middle school and high school.
Blood pressure measurement
For the blood pressure (BP) measurement, we used a standard protocol, as many guidelines have recommended. The protocol stated that the participants should be at rest for at least five minutes and not consume caffeinated drinks or exercise before the BP measurement. Omron Healthcare automatic electronic sphygmomanometers (HEM-907; Omron Healthcare, Kyoto, Japan) were used to measure participants’ BP. We used the average of three BP measurements in all analyses.
Waist circumference measurement and body mass index calculation
While measuring height and weight, the study subjects were asked to wear light clothes and remove their shoes. We recorded participants’ height and weight to an accuracy of 0.1 cm and 0.1 kg. Subjects’ waist circumferences (WC) were also measured with nonelastic tape at the umbilicus (0.1 cm). Body mass index (BMI) was calculated as body weight (kg)/ height (m) 2.
Blood sample and biochemistry test
Participants were required to fast for at least twelve hours, and fasting blood specimens were taken in the morning. As previously described, we used enzymatic analysis to exam total cholesterol (TC), triglycerides (TGs), fasting blood glucose (FPG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) with an automatic biochemical analyzer and biochemical indicators [8, 9]. The technician calibrated the laboratory equipment before use, and specimen analyses were repeated using blind specimens.
Transthoracic Echocardiography Evaluation
We recorded M-mode measurements at the end of diastole and the end of systole according to the recommendations of the American Society of Echocardiography (ASE) [13]. The details of the procedures were previously described [8]. The average of five consecutive cardiac cycles was used to calculate the echocardiographic data. A single cardiologist read the images without knowing the subjects’ clinical characteristics.
Definitions
Currently, there is no uniform definition of HHcy. According to the WHO standard, the average level of Hcy for healthy adults is 5–15 μmol/L, with an Hcy level >15 μmol/L representing HHcy [14]. MetS is diagnosed according to the modified NCEP ATP III criteria [15]. At least 3 or more of the following 5 components are needed to diagnose MetS:
Components
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Criteria
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Elevated WC
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≥ 102 cm (Male);
≥ 88 cm (Female)
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Elevated TG
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> 150 mg/dL (1.7 mmol/L)
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Reduced HDL-C
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< 40 mg/dL or 1.04 mmol/L (Male)
< 50 mg/dL or 1.29 mmol/L (Female)
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Hypertension or elevated BP
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≥130/85 mmHg
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Diabetes or elevated FPG
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≥ 5.6 mmol/L
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WC ≥ 88 cm for females and WC ≥ 102 cm for males is defined as abdominal obesity [16].
TC ≥ 6.21 mmol/L (240 mg/dL) means high TC, while high LDL-C is diagnosed as the concentration of LDL-C ≥ 4.16 mmol/L (160 mg/dL). According to the WHO criteria, FPG ≥ 7 mmol/L (126 mg/dL) and/or being treated for diabetes was diagnosed as diabetes [17].
The LVM was calculated according to the formula presented by Devereux and Reichek [18]:
LVM (g)=1.04×[(LV end-diastolic dimension (LVEDD)*+end-diastolic interventricular septum thickness (IVSd)#+end-diastolic LV posterior wall septum thickness (PWd)$)3-(LVEDD)3]-13.6
|
* LVEDD is the end-diastolic LV internal diameter; # IVSd is the ventricular septal thickness; $ PWd is the posterior LV wall thickness
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The LVM was indexed by both body surface area (LVMI) and height raised to a power of 2.7 (LVMH2.7), as suggested by De Simone et al. [18].
We used a limit of 51 gm-2.7 in either sex to separate normal left ventricular thickness from LVH because its value is related to prognostics [19]. High LVMI was defined as LVMI larger than 115 g/m2 for male patients and larger 95 g/m2 for female patients, as defined by the ASE recommendations. Participants who never smoked or drank were defined as never smokers or never drinkers, and those who were currently smoking and drinking were defined as current smokers or current drinkers. Physical activity was evaluated using questions that have been described in many previous studies and were similar to those used and validated in the “Seven Countries Study” [20].