Jee-Seon Shim

Dietary assessment methods in epidemiologic studies

Diet is a major lifestyle-related risk factor of various chronic diseases. Dietary intake can be assessed by subjective report and objective observation. Subjective assessment is possible using open-ended surveys such as dietary recalls or records, or using closed-ended surveys including food frequency questionnaires. Each method has inherent strengths and limitations. Continued efforts to improve the accuracy of dietary intake assessment and enhance its feasibility in epidemiological studies have been made. This article reviews common dietary assessment methods and their feasibility in epidemiological studies.

Reproducibility and validity of an FFQ developed for the Korea National Health and Nutrition Examination Survey (KNHANES)

OBJECTIVE We aimed to evaluate the reproducibility and validity of the newly developed FFQ for the Korean National Health and Nutrition Examination Survey (KNHANES) and to estimate the measures calibration factors. DESIGN The 109-item FFQ was administered twice, approximately 9 months apart. We also collected four seasonal 3 d dietary records (DR) as a reference method. Correlation coefficients and joint classification were computed to compare intakes of energy, thirteen nutrients and eleven food groups between the two FFQ to evaluate reproducibility. For validity, de-attenuated and energy-adjusted correlation, joint classification and Bland-Altman statistics were calculated for energy and nutrients between the first FFQ and the DR. To calibrate the FFQ, we performed a linear regression analysis in which the DR were the dependent variables and FFQ, age and sex were the independent variables. SETTING Seoul metropolitan area, Republic of Korea. SUBJECTS A total of 126 adults aged 20-65 years. RESULTS The average correlation coefficients measuring reproducibility were 0·54 for nutrients and 0·57 for food groups. The mean correlation coefficient measuring validity was 0·40 for all nutrients between the first FFQ and the DR. On average, 75 % of the participants were classified into the same or adjacent quartiles, while 5 % of the participants were grossly misclassified. The mean energy and nutrient intakes estimated by the calibrated FFQ were similar to the means estimated by the DR. CONCLUSIONS The newly developed FFQ for assessing dietary intake in the KNHANES has acceptable reproducibility and modest validity compared with a 12 d DR collected over a 9-month period.

Metabolic syndrome and its association with white blood cell count in children and adolescents in Korea: the 2005 Korean National Health and Nutrition Examination Survey.

BACKGROUND AND AIMS To estimate the prevalence of metabolic syndrome (MS) and determine its association with white blood cell (WBC) count as a marker of low-grade systemic inflammation in children and adolescents in Korea. METHODS AND RESULTS We investigated the prevalence of MS and its association with WBC count in 928 children and adolescents. MS was defined as having 3 or more conditions based on the modified criteria of the National Cholesterol Education Program-Adult Treatment Panel III (NCEP-ATP III). The odds ratios (ORs) for MS were also calculated using multivariate logistic regression analysis across WBC count quartiles (Q1, <5200; Q2, 5200-6100; Q3, 6200-7200; and Q4, >or=7300 cells/microL for boys; Q1, <5200; Q2, 5200-6000; Q3, 6100-7000; and Q4, >or=7100 cells/microL for girls). The prevalence of MS in children and adolescents in Korea was 6.7% (8.5% in boys, 4.5% in girls, P<0.001). MS was more prevalent in overweight and obese children and adolescents in both boys and girls. The mean WBC counts continuously increased with each additional component of MS in both boys and girls. The ORs (95% CIs) for MS in each WBC quartile were 1.00, 1.56 (0.43-5.67), 4.47 (1.42-14.07), and 5.25 (1.71-16.07) in boys and 1.00, 1.05 (0.15-7.61), 2.89 (0.55-15.17), and 7.47 (1.61-36.67) in girls after adjusting for age, household income, and residential area. CONCLUSION In summary, this study shows that a substantial number of children and adolescents in Korea have MS, and elevated WBC count may be a surrogate marker for MS.

Reading nutrition labels is associated with a lower risk of metabolic syndrome in Korean adults: the 2007-2008 Korean NHANES.

BACKGROUND AND AIMS Several studies demonstrated that reading nutrition labels was associated with healthier food choices, despite some controversy. This study investigated the association between the use of nutrition labels and metabolic syndrome (MetS) in Korean adults. METHODS AND RESULTS This cross-sectional study included 7756 individuals who participated in the 2007-2009 Korean National Health and Nutrition Examination Survey (KNHANES). A self-reported questionnaire was used to determine participants awareness of nutrition labels. Modified Asian criteria based on a harmonizing definition of MetS were adopted. Individuals in the group that read nutrition labels (the Reading Group) were youngest and leanest, but their daily caloric intake fell between that of the group that did not read nutrition labels (the Non-Reading Group) and the group that did not know about them (the Not-Knowing Group). The prevalence of MetS was 16.8% in the Reading Group, 27.2% in the Non-Reading Group, and 47.3% in the Not-Knowing Group. In comparison to participants in the Reading Group, the odds ratios (95% confidence interval) for MetS in the participants in the Non-Reading Group and Not-Knowing Group were 1.85 (1.60-2.14) and 4.44 (3.79-5.20), respectively, when not adjusted. The relationship between the use of nutrition labels and MetS remained statistically significant even after adjusting for covariates such as age, sex and socioeconomic status including household income and education level [1.27 (1.05-1.53) in the Non-Reading Group and 1.34 (1.05-1.70) in the Not-Knowing Group]. CONCLUSION Reading nutrition labels appeared to be associated with a lower prevalence of MetS in a nationally representative sample of Korean adults.

Mortality and Incidence of Malignancy in Korean Patients with Rheumatoid Arthritis

Objective. To determine the standardized mortality ratio (SMR) and standardized incidence ratio (SIR) for malignancy in Korean patients with rheumatoid arthritis (RA). Methods. We enrolled 1534 patients with RA who fulfilled the American College of Rheumatology criteria, from October 2001 to December 2007. Baseline assessment included sociodemographic variables, laboratory findings including rheumatoid factor, anticitrullinated protein antibody, functional class, radiological stage, medication, and the Korean version of the Health Assessment Questionnaire. We used the national mortality rate from 2001 to 2007 from the Korean National Statistical Office (KNSO) and the incidence rate from the Korean Central Cancer Registry (KCCR) from 2001 to 2007 as comparison data for estimates of SMR and SIR. Confidence intervals were calculated based on the Poisson distribution. Results. There were 57 deaths in 6683 person-years of followup. The number of expected deaths (derived from the KNSO) was 42.33 and the SMR for patients with RA was 1.35 (95% CI 1.02–1.74). The main causes of death were malignancy, cardiovascular disease, and respiratory disease. In the cause-specific SMR, deaths from respiratory disease, especially from interstitial lung disease (ILD) and pneumonia, were significantly higher than expected: 4.66 (95% CI 2.13–8.85) for all respiratory disease, 18.18 (95% CI 2.20–65.64) for ILD, and 10.26 (95% CI 2.79–26.26) for pneumonia. Thirty malignancies had occurred in 1501 patients. The number of expected malignancies derived from the KCCR was 34.91, yielding a SIR for cancer of 0.86 (95% CI 0.58–1.23). Conclusion. Our study demonstrates that the SMR was slightly higher in patients with RA, but the incidence rates of malignancies were not significantly different from the general population. But deaths from respiratory diseases were significantly higher.

Effects of Age, Sex, and Menopausal Status on Blood Cholesterol Profile in the Korean Population

Background and Objectives To investigate age-specific and sex-specific distributions of blood cholesterol in the general Korean population. Subjects and Methods We analyzed data for 8284 men and 9246 women aged ≥10 years who participated in the fifth (2010-2012) Korea National Health and Nutrition Examination Survey. Age-specific means, medians, and selected percentiles were calculated for men, premenopausal women, and postmenopausal women. Results Median total cholesterol (TC) level increased with age across all age groups, from 147 to 196 mg/dL in males and from 159 to 210 mg/dL in females. Triglyceride (TG) levels increased with age in females; however, in males, TG levels rapidly increased during young adulthood, peaked at 50-54 years, and then decreased. High density lipoprotein-cholesterol (HDL-C) levels were higher in females than in males and decreased with increasing age in both males and females. Low density lipoprotein-cholesterol (LDL-C) levels increased with age across all age groups, from 89 to 127 mg/dL in males and from 82 to 113 mg/dL in females. Lipoprotein-cholesterol fraction (TC/HDL-C, LDL-C/HDL-C, TG/HDL-C, non-HDL-C) levels increased with age in females, but increased more rapidly in males during young adulthood and decreased after middle age. Conclusion Blood cholesterol levels and lipoprotein-cholesterol fractions present different distributions by age, sex, and menopausal status.

Relationship between non‐alcoholic fatty liver disease and pulmonary function

Background:  It has been observed that non‐alcoholic fatty liver disease (NAFLD) is associated with an increased risk of cardiovascular disease and insulin resistance. Pulmonary function is also known to be related with cardiovascular disease and metabolic syndrome.

Inter-Arm Difference in Brachial Blood Pressure in the General Population of Koreans

Background and Objectives We investigated the inter-arm difference in blood pressure of the general Korean population to identify associated factors. Subjects and Methods A total of 806 participants aged 30 to 64 years without history of major cardiovascular disease were analyzed in this cross-sectional study. They participated in the Cardiovascular and Metabolic Disease Etiology Research Center cohort study that began in 2013. Brachial blood pressure was measured simultaneously for both arms using an automated oscillometric device equipped with two cuffs in seated position. After five minutes of rest, systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured three times. The average of the three measurements was used for analysis. Multivariate logistic regression models were used to identify factors associated with inter-arm differences in blood pressure. Results The mean inter-arm difference was 3.3 mmHg for SBP and 2.0 mmHg for DBP. Large inter-arm differences (≥10 mmHg) in SBP and in DBP were found in 3.7% and 0.9% of subjects, respectively. A large inter-arm difference in SBP was associated with mean SBP (p=0.002) and C-reactive protein (p=0.014) while a large inter-arm different in DBP was only associated with body mass index (p=0.015). Sex, age, and anti-hypertensive medication use were not associated with differences in inter-arm blood pressure. Conclusion Large inter-arm difference in blood pressure is only present in a small portion of healthy Korean adults. Our findings suggest that high SBP, chronic inflammation, and obesity may be associated with larger difference in inter-arm blood pressure.

Association of Insulin Resistance with Lower Bone Volume and Strength Index of the Proximal Femur in Nondiabetic Postmenopausal Women

Background Type 2 diabetes mellitus is associated with an increased risk of osteoporotic fracture despite relatively preserved bone mineral density (BMD). Although this paradox might be attributed to the influence of insulin resistance (IR) on bone structure and material properties, the association of IR with femur bone geometry and strength indices remains unclear. Methods Using data from the Cardiovascular and Metabolic Disease Etiology Research Center cohort study, we conducted a cross-sectional analysis among nondiabetic postmenopausal women. IR was estimated using the homeostasis model assessment of IR (HOMA-IR). Compartment-specific volumetric BMD (vBMD) and bone volume of proximal femur were measured using quantitative computed tomography. The compressive strength index (CSI), section modulus (Z), and buckling ratio of the femoral neck were calculated as bone strength indices. Results Among 1,008 subjects (mean age, 57.3 years; body mass index [BMI], 23.6 kg/m2), BMI, waist circumference, and vBMD of the femoral neck and total hip increased in a linear trend from the lowest (<1.37) to highest (≥2.27) HOMA-IR quartile (P<0.05 for all). The HOMA-IR showed an independent negative association with total bone volume (standardized β=−0.12), cortical volume (β=−0.05), CSI (β=−0.013), and Z (β=−0.017; P<0.05 for all) of the femoral neck after adjustment for age, weight, height, physical activity, and vitamin D and high-sensitivity C-reactive protein levels. However, the association between HOMA-IR and vBMD was attenuated in the adjusted model (femoral neck, β=0.94; P=0.548). Conclusions Elevated HOMA-IR was associated with lower cortical bone volume and bone strength indices in nondiabetic postmenopausal women, independent of age and body size.

Serum 25-Hydroxyvitamin D Concentration Is Independently Inversely Associated with Insulin Resistance in the Healthy, Non-Obese Korean Population.

Background We evaluated the associations between 25-hydroxyvitamin D (25(OH)D) concentrations in serum and insulin resistance in the healthy Korean population. Methods We conducted this cross-sectional analysis in 1,807 healthy Korean people (628 men and 1,179 women) aged 30 to 64 years in the Cardiovascular and Metabolic Disease Etiologic Research Center study. All participants were assessed for 25(OH)D, fasting glucose, and insulin levels, and completed a health examination and lifestyle questionnaire according to standard procedures. Insulin resistance was defined as the homeostasis model assessment insulin resistance higher than the 75 percentile. Results Compared to those in the highest tertile (≥14.3 ng/mL), the odds ratio (OR) for insulin resistance was 1.37 (95% confidence interval [CI], 1.01 to 1.86) for the 1st tertile (<9.7 ng/mL) and 1.19 (95% CI, 0.08 to 1.62) for the 2nd tertile (9.7 to 14.3 ng/mL) after adjusting for age, gender, waist circumference, alcohol consumption, smoking status, physical exercise, season, and cohort. After stratification of the subjects by adiposity, these associations remained only in non-obese subjects (lowest tertile vs. highest tertile, multivariable OR, 1.64; 95% CI, 1.05 to 2.56). Conclusion Serum 25(OH)D has an independent inverse association with insulin resistance in the healthy, non-obese Korean population, even among people with vitamin D insufficiency.