Study population
The Health Examinees (HEXA) study is a part of the Korea Genome Epidemiology Study (KoGES) and is a population-based cohort study that prospectively recruited participants from 2004 to 2013 at 38 health examination centers and training hospitals located in 8 regions and included the Korean population aged 40 to 69 years [8]. Analysis was restricted to the Health Examinees-Gem (HEXA-G) participants which were defined as followed: we excluded (1) 8 sites (n = 9,370) that only participated in the pilot study years 2004–2006, (2) 8 sites (n = 12,205) that did not meet the HEXA biospecimen quality control criteria (i.e., different testing protocols), and (3) 5 sites (n = 8,799) that had participated in the study for less than 2 years. A total of 139,348 participants were included in the HEXA-G data. Among HEXA-G participants, we excluded 1,391 participants who had no information on anthropometric measurements of height, weight, waist circumference, and hip. Then, an additional 3,762 participants had no information on blood pressure or biochemical measurements of the blood specimen, such as fasting glucose, triglyceride, and high-density lipoprotein. We conducted all analyses among the 134,195 participants who remained after exclusion.
Data collection
Participants were questioned by trained interviewers and responded to a structured questionnaire on general characteristics and past medical history. Anthropometric measurements and biochemical assessments of fasting blood glucose, triglyceride and high-density lipoprotein cholesterol were also conducted for all participants. Weight and height were directly measured using electronic measuring instruments with digital scales and were read up to one decimal place. Waist and hip circumference were obtained by a measuring tape of a horizontal plane and were read up to one decimal place. Systolic and diastolic blood pressure was measured twice using the standardized mercury sphygmomanometer on one arm in the sitting position and finally determined as the average of the two readings.
Definition of terms
Participants meeting at least one of the following criteria were considered to have multiple metabolic dysfunctions: defined hypertension [9], those who had a systolic blood pressure higher than 140 mmHg, a diastolic blood pressure higher than 90 mmHg, or those who reported taking antihypertensive medication; hyperglycemia [10], those who had a fasting blood glucose higher than 126 mg/dL or who reported taking antidiabetic medication; and hyperlipidemia, those who had a triglyceride level higher than 150 mg/mL, a high density lipoprotein cholesterol lower than 40 mg/dL, or those who reported taking medication for dyslipidemia.
Statistical analysis
We calculated the mean and standard deviation for demographic, anthropometric, blood pressure and biochemical characteristics. The inclusion of a large population in this study would reduce the meaningfulness of statistical significance for differences in the general characteristics between sexes. For this reason, we did not present a p-value in the descriptive analysis of Table 1 and 2. Receiver operating characteristic (ROC) curves were plotted for obesity indices to identify the best obesity index that discriminates the presence of cardiovascular risk factors. The area under the receiver operating characteristic curves (AUCs) was used as a summary measure of accuracy to evaluate the performance of obesity indices for the discrimination of participants with metabolic dysfunctions. Youden’s J statistics [11] was used to determine the optimal cut-off values for the obesity indices. Youden’s index was calculated as sensitivity + specificity - 1 and equal to the height above the line of chance on the curves. We considered the optimal cut-off values at the corresponding value for the maximum of the Youden index. All statistical analyses were stratified by sex. We analyzed data using SAS version 9.4 (SAS Institute Inc., Cary, NC, USA) for the calculation of optimal cut-points and R software for the calculation of the AUCs and the visualization of the ROC.
Table 1
Anthropometric indices of obesity and metabolic characteristics among HEXA-G participants by sex, mean ± standard deviation.
| Men (N = 45,052) | Women (N = 89,143) |
Age, year | 53.6 | ± | 8.38 | 52.3 | ± | 7.76 |
Height, cm | 168.8 | ± | 5.74 | 156.5 | ± | 5.26 |
Weight, cm | 69.6 | ± | 9.23 | 57.9 | ± | 7.66 |
Waist circumference, cm | 85.7 | ± | 7.52 | 78.3 | ± | 8.17 |
Hip circumference, cm | 96.0 | ± | 5.64 | 93.5 | ± | 5.69 |
Body mass index, kg/m2 | 24.4 | ± | 2.75 | 23.6 | ± | 2.94 |
Waist to hip ratio | 0.89 | ± | 0.05 | 0.84 | ± | 0.06 |
Waist to height ratio | 0.51 | ± | 0.04 | 0.50 | ± | 0.06 |
Conicity index, m3/2/kg1/2 | 1.23 | ± | 0.06 | 1.18 | ± | 0.08 |
Systolic blood pressure, mmHg | 125.7 | ± | 14.35 | 120.6 | ± | 15.17 |
Diastolic blood pressure, mmHg | 78.7 | ± | 9.68 | 74.7 | ± | 9.66 |
Fasting serum glucose level, mg/dL | 99.3 | ± | 24.28 | 92.7 | ± | 18.47 |
Triglyceride, mg/dL | 151.4 | ± | 111.41 | 112.5 | ± | 74.18 |
High-density lipoprotein cholesterol, mg/dL | 49.4 | ± | 12.09 | 56.1 | ± | 12.80 |
Table 2
Definition and prevalence of hypertension, diabetes, hyperglycemia, hyperlipidemia and cardiovascular risk factors among HEXA-G participants by sex, n (%).
| Definition | Men | Women |
Hypertension | Systolic blood pressure higher than 140 mmHg, diastolic blood pressure higher than 90 mmHg or those who reported taking antihypertensive medication | 15,310 (34.0) | 21,386 (24.0) |
Hyperglycemia | Fasting glucose higher than 126 mg/dL or those who reported taking antidiabetic medication | 5,196 (11.5) | 5,319 (6.0) |
Hyperlipidemia | Triglyceride higher than 150 mg/mL, high density lipoprotein cholesterol lower than 40 mg/dL or those who reported taking medication for dyslipidemia | 21,794 (48.4) | 39,768 (44.6) |
Cardiovascular risk factors | Having at least one of the above | 29,605 (65.7) | 49,680 (55.7) |