Associations of resistance training levels with low muscle mass: a nationwide cross-sectional study in Korea

BACKGROUND

Low muscle mass is associated with adverse health outcomes such as functional decline and all-cause mortality. This study investigated the relationship between the risk of low muscle mass and the training period and/or frequency of resistance training (RT).

METHODS

We included 126,339 participants (81,263 women) from nationwide cohorts in Korea. Low muscle mass was defined based on the fat-free mass index. To investigate the presence of an inverse dose-response relationship between RT levels and the risk of low muscle mass, the training period (months) and frequency (per week) of RT were used. Multiple logistic regression models were used to assess the risk of low muscle mass according to the RT levels.

RESULTS

Prevalence rates for low muscle mass in our study population were 21.27% and 6.92% in men and women, respectively. When compared with not performing RT, performing RT for 3-4 days/week and ≥5 days/week decreased the risk of low muscle mass by 22% and 27%, respectively, and performing RT for 12-23 months and ≥24 months decreased the risk by 19% and 41%, respectively. When simultaneously considering both training period and frequency, performing RT for either 3-4 days/week or ≥5 days/week was significantly related to risk reduction, provided that the training period was at least 1 year. Importantly, performing RT for more than 2 years resulted in an additional risk reduction. However, there was no additional effect of performing RT for ≥5 days/week compared to 3-4 days/week, regardless of whether the RT duration was 1-2 years or more than 2 years.

CONCLUSIONS

Since performing RT for 5 days/week or more did not yield any additional effects on the risk of low muscle mass, performing RT for 3-4 days/week was sufficient to prevent low muscle mass. The effectiveness of this preventive measure can be further enhanced by engaging in long-term RT, specifically for more than 2 years.

Sex-based differences in the association of leisure-time physical activity with the risk of depression: the Ansan and Ansung study of the Korean Genome and Epidemiology Study (KoGES)

Objective

Depression is a serious mental disorder which is the leading cause of suicide. This study investigated the association between incident depression and 4-year leisure-time physical activity (PA) levels and/or resistance training (RT).

Methods

This community-based Korean cohort included 3,967 participants without depression at baseline. The average PA-time (the total duration of moderate-intensity leisure-time PA) up to 4 years prior to baseline enrollment was calculated to evaluate the cumulative levels of PA. Participants were divided into four groups based on their average PA-time: "Non-PA," " <150 min/week," "150-299 min/week," and "≥300 min/week." Furthermore, based on compliance to PA guidelines (≥150 min/week of PA-time) and participation in RT, the participants were categorized into four subgroups: "Low-PA," "Low-PA+RT," "High-PA," and "High-PA+RT." A multivariate Cox proportional hazards regression model was used to assess the 4-year incidence of depression according to leisure-time PA levels and/or regularity of RT.

Results

During the mean 3.72 ± 0.69 years of follow-up, 432 participants (10.89%) developed depression. In women, performing 150-299 min/week of moderate-intensity leisure-time PA was associated with a 38% risk reduction for incident depression (HR, 0.62; CI, 0.43-0.89; p < 0.05), whereas more than 300 min/week of that was related to a 44% risk reduction for incident depression (HR, 0.56; CI, 0.35-0.89; p < 0.05) as compared to that in the Non-PA group. However, in men, there was no significant relationship between the amount of leisure-time PA per week and the risk of incident depression. Moreover, in both sexes, RT had no significant effect on depression in either the Low-PA or High-PA group.

Conclusions

There was an inverse dose-response association between leisure-time PA levels and incident depression only in women, whereas adding RT to high levels of PA had no significant effect on depression in either sex.

Weight Changes and Unhealthy Weight Control Behaviors Are Associated With Dysmenorrhea in Young Women

BACKGROUND

This study aimed to evaluate the prevalence of dysmenorrhea and to investigate the effect of weight changes or unhealthy weight control behaviors on dysmenorrhea in young Korean women.

METHODS

We used large-scale data of women, aged 14 to 44 years, who participated in the Korean Study of Women's Health-Related Issues. Dysmenorrhea was measured using a visual analog scale and was categorized as none, mild, moderate, and severe according to the severity. Weight changes and unhealthy weight control behaviors (any of the behaviors, fasting/meal skipping, drugs, the use of unapproved dietary supplements, and one-food diets) over the past year were self-reported. We used multinomial logistic regression to investigate the association between weight changes or unhealthy weight control behaviors and dysmenorrhea.

RESULTS

Of the 5,829 young women participating in the study, 5,245 (90.0%) participants experienced dysmenorrhea [2,184 (37.5%) had moderate and 1,358 (23.3%) had severe]. After adjusting for confounders, the odds ratios for moderate and severe dysmenorrhea in participants with weight changes ≥ 3 kg (vs. < 3 kg) were 1.19 (95% confidence interval: 1.05-1.35) and 1.25 (95% confidence interval: 1.08-1.45), respectively. The odds ratios in participants with any unhealthy weight control behaviors were 1.22 (95% confidence interval: 1.04-1.42) and 1.41 (95% confidence interval: 1.19-1.67) for those with moderate and severe dysmenorrhea, respectively.

CONCLUSION

Weight changes (≥ 3 kg) or unhealthy weight control behaviors are common among young women, which may adversely affect dysmenorrhea. Therefore, attention needs to be paid to excessive weight changes and unhealthy weight control behaviors to improve dysmenorrhea in young women.

Association of leisure-time physical activity and resistance training with risk of incident hypertension: The Ansan and Ansung study of the Korean Genome and Epidemiology Study (KoGES)

Hypertension is the most common preventable risk factor for the onset of cardiovascular disease and mortality. We aimed to investigate the association between incident hypertension and 4-year leisure-time physical activity (PA) levels and resistance training (RT). In this community-based Korean cohort, 5,075 participants without hypertension were included. To evaluate cumulative PA, the average PA time (the total time of moderate-intensity leisure-time PA) at baseline, 2-year follow-up, and 4-year follow-up were calculated. Based on participation in RT and compliance to PA guidelines (≥150 min/week of PA time), the participants were divided into the following four groups: Low-PA, Low-PA+RT, High-PA, and High-PA+RT. A multivariate Cox proportional hazards regression model was used to evaluate the 12-year incidence of hypertension in relation to leisure-time PA levels and RT regularity. During a mean 7.86 ± 4.20-year follow-up, 2,544 participants (1,366 women) were diagnosed with hypertension. Compared with Low-PA, High-PA, and High-PA+RT decreased the risk for hypertension by 30 and 39%, respectively. Participation in RT without compliance to PA guidelines did not affect the incidence of hypertension. The additive effect of RT on hypertension in the High-PA group was further examined. Although sex-based comparisons indicated that men had a significantly longer training period for RT than women, an additional reduction in the risk for hypertension in relation to the addition of RT was observed only in women (35%). PA may confer protective effects against hypertension, whereas the addition of RT to high levels of PA can further reduce the risk for hypertension in women.

Relative Handgrip Strength is Inversely Associated with Hypertension in Consideration of Visceral Adipose Dysfunction: A Nationwide Cross-Sectional Study in Korea

This study investigated the associations of relative handgrip strength (rHGS) and hypertension. Individual differences in visceral adipose dysfunction (VAD) were evaluated to verify whether rHGS was associated with a reduction in the risk of hypertension, even in individuals with VAD. We included 77,991 participants (50,616 women) from nationwide cohorts in Korea. Participants were categorized into three groups based on sex-specific tertiles of rHGS (Low, Mid, and High). The visceral adiposity index (VAI) was used to evaluate VAD. The multiple logistic regression model was used to assess the risk of hypertension. High rHGS is associated with reduction of hypertension risk in 38 and 26% of men and women, respectively, although rHGS was significantly low in women compared to men. The benefit of rHGS was observed from middle-aged to older participants in both sexes. High rHGS is associated with risk reduction for hypertension in both VAD and non-VAD groups. In the VAD group, compared to Low rHGS, High rHGS was associated with 32 and 22% risk reductions in hypertension in men and women, respectively, and these associations remained significant even when classified according to age, such as in middle-aged and older subgroups. Therefore, the present study suggests that high levels of rHGS are significantly associated with a reduced risk of hypertension even in participants with VAD. Thus, maintaining a higher level of rHGS may be associated with protective benefits against hypertension.

Protective Effect of Leisure-Time Physical Activity and Resistance Training on Nonalcoholic Fatty Liver Disease: A Nationwide Cross-Sectional Study

Background: Nonalcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease. The present study aimed to investigate the association of NAFLD with leisure-time physical activity (PA) levels and resistance training (RT). Methods: We used data from large nationwide cohorts in Korea. NAFLD was defined based on the Framingham steatosis index. Participants were categorized into four groups based on RT frequency and adherence to PA guidelines (≥150 min/week of moderate-intensity PA): Low-PA, Low-PA+RT, High-PA, and High-PA+RT. Multiple logistic regression models were used to assess the risk of NAFLD according to leisure-time PA levels and regularity of RT. Results: When compared with Low-PA, High-PA decreased the risk of NAFLD by 17%, and High-PA+RT further decreased the risk by 30%. However, the additional reduction in risk associated with the addition of RT was observed in men (19%), but not in women. In the High-PA group, men had a significantly higher training frequency and period for RT than women. Conclusions: Following the PA guideline may confer protective effects against NAFLD, while adding RT to High-PA can further decrease the risk of NAFLD. Sex-based differences in NAFLD risk in the High-PA+RT group may be due to the differences in the frequency and period of RT.

Use of Menstrual Sanitary Products in Women of Reproductive Age: Korea Nurses' Health Study

OBJECTIVES

The use of menstrual hygiene products and its effect on women's health remains under studied. Patterns of menstrual hygiene product use and the rationale behind choices among Korean women aged 18-45 years were examined.

METHODS

This cross-sectional study was a part of the Korea Nurses' Health Study. A total of 20,613 nurses participated, and 8,658 nurses participated in Module 7 which included a menstrual hygiene products-related survey. The data were collected through the mobile survey using a self-reported questionnaire. Participants' use of menstrual hygiene products and related characteristics were analyzed using frequency (percentage) or mean (SD).

RESULTS

The most common types of menstrual hygiene products across all age groups were disposable menstrual pads (89.0%), followed by cloth menstrual pads (4.5%), tampons (4.2%), and only 1.6% used a menstrual cup. Disposable menstrual pads were the most common across all age groups, but in those aged under 30 years this was followed by tampon use (6%). The most important criteria when choosing a menstrual hygiene product was comfort for disposable menstrual pads (31.3%) and tampons (41.5%), natural ingredients or organic products for cloth menstrual pads (51.4%), and custom fit for the menstrual cup (50.7%). However, for all menstrual hygiene products (except cloth menstrual pads), there was a higher proportion of anxiety than perception of safety, and low awareness of toxic shock syndrome.

CONCLUSION

It is important for women to use menstrual hygiene products with confidence. More research is needed to better understand potential health effects of menstrual hygiene products.

Presenting characteristics and clinical outcome of patients with COVID-19 in South Korea: A nationwide retrospective observational study

BACKGROUND

More than 13,000 cases were reported to be infected with COVID-19 by RT-PCR in South Korea. Most studies report clinical characteristics of hospitalized patients with COVID-19; the full spectrum of disease severity has thus not yet been well described.

METHODS

Using retrospective observational methods, this study analyzed factors affecting early clinical symptoms, clinical progress, and severity of disease for COVID-19 positive patients released from quarantine to provide information on establishing optimized care for new patients. The medical data of 7803 laboratory-confirmed patients who had been discharged or died by April 30, 2020 were analyzed using multivariate logistic regression analysis.

FINDINGS

On admission, 7383 (94•5%) patients were asymptomatic or showed mild illness, and 372 (4•8%) patients were severe illness. Also, 48 (0 0•6%) were hospitalized with critically ill when diagnosed. Most patients with asymptomatic or mild illness on admission remained mild until discharge, 253 (3•4%) progressed to severe illness, and 83 (1•1%) died in hospital. However, the case fatality were 29•8% and 62•5% in severe and critically ill patients, respectively. At admission, 73•0% of hospitalized patients had symptoms; most common were cough (42•5%), sputum (28•8%), and fever (20•1%). Only 35•2% of laboratory confirmed patients admitted to the temporary care facility complained of symptoms. Increasing odds of being critically ill was associated with older age (OR 28•93, 95% CI 13•34-62•75 for age >70y, vs. age <50 y; p<0•0001), being male (OR 2•15, 95% CI1•59-2•89; p<0•0001), fever (OR 2•52, 95% CI 1.84-3•45; p<0•0001), and shortness of breath (OR 7•40, 95% CI 5•37-10•19; p<0•0001). Comorbid illness significantly increased risk of critical illness or death.

INTERPRETATION

Most cases were discharged as asymptomatic or recovered from mild illness, and only 9•7% developed severe disease requiring oxygen therapy or more. Case fatality rate was 2•9%, and markedly increased in those over age 50. Risk factors such as age, sex, fever, shortness of breath, and underlying disease can be useful in predicting future clinical severity. Additionally, the number of confirmed asymptomatic COVID-19 patients significantly contribute to continued spread.

FUNDING

none.

Impact of atrial fibrillation in patients with heart failure and reduced, mid-range or preserved ejection fraction

Objective

To determine the prognostic value of atrial fibrillation (AF) in patients with heart failure (HF) and preserved, mid-range or reduced ejection fraction (EF).

Methods

Patients hospitalised for acute HF were enrolled in the Korean Acute Heart Failure registry, a prospective, observational, multicentre cohort study, between March 2011 and February 2014. HF types were defined as reduced EF (HFrEF, LVEF <40%), mid-range EF (HFmrEF, LVEF 40%–49%) or preserved EF (HFpEF, LVEF ≥50%).

Results

Of 5414 patients enrolled, HFrEF, HFmrEF and HFpEF were seen in 3182 (58.8%), 875 (16.2%) and 1357 (25.1%) patients, respectively. The prevalence of AF significantly increased with increasing EF (HFrEF 28.9%, HFmrEF 39.8%, HFpEF 45.2%; p for trend <0.001). During follow-up (median, 4.03 years; IQR, 1.39–5.58 years), 2806 (51.8%) patients died. The adjusted HR of AF for all-cause death was 1.06 (0.93–1.21) in the HFrEF, 1.10 (0.87–1.39) in the HFmrEF and 1.22 (1.02–1.46) in the HFpEF groups. The HR for the composite of all-cause death or readmission was 0.97 (0.87–1.07), 1.14 (0.93–1.38) and 1.03 (0.88–1.19) in the HFrEF, HFmrEF and HFpEF groups, respectively, and the HR for stroke was 1.53 (1.03–2.29), 1.04 (0.57–1.91) and 1.90 (1.13–3.20), respectively. Similar results were observed after propensity score matching analysis.

Conclusions

AF was more common with increasing EF. AF was seen to be associated with increased mortality only in patients with HFpEF and was associated with an increased risk of stroke in patients with HFrEF or HFpEF.

Trial registration number

NCT01389843

Predicting stroke and death in patients with heart failure using CHA2DS2-VASc score in Asia

Background

The CHA₂DS₂-VASc score is used to assess risk of mortality as well as to stratify risk of stroke in patients with atrial fibrillation (AF). This study evaluated whether CHA₂DS₂-VASc score was predictive of 1 and 2 year risks of stroke and death in Asian patients with heart failure (HF).

Methods

Patients hospitalized for HF were enrolled in the Korean Acute Heart Failure (KorAHF) registry, a prospective observational multicenter cohort study, between March 2011 and February 2014. Patients with a history of cancer before hospitalization for HF were excluded. The discriminatory properties of the CHA₂DS₂-VASc score were quantified using C-statistics.

Results

The study included 5158 patients with HF, 2091 with and 3067 without AF. Rates of stroke in these two groups were 4.5 and 2.8%, respectively, after 1 year, and 5.5 and 3.4%, respectively, after 2 years. Each 1-point increase in CHA₂DS₂-VASc score was associated with significantly increased risks of stroke and all-cause death in HF patients with and without AF (p-value < 0.05). The C-statistics of the CHA₂DS₂-VASc score for all-cause death in patients with and without AF were 0.600 and 0.630, respectively, at 1 year and 0.626 and 0.635, respectively, at 2 years. The C-statistics for stroke ranged from 0.593 to 0.639.

Conclusions

Among patients with incident HF with and without AF, CHA₂DS₂-VASc score was significantly associated with the risks of stroke and death. However, CHA₂DS₂-VASc score was only a modest predictor of stroke and death, indicating the need for studies evaluating modified CHA₂DS₂-VASc scores. The majority of strokes occurred relatively shortly after hospitalization for HF and that mortality rates in patients with HF remain high. Thus, early treatment after HF to prevent stroke is essential.

Electronic supplementary material

The online version of this article (10.1186/s12872-019-1178-0) contains supplementary material, which is available to authorized users.

Risk prediction for 30-day heart failure-specific readmission or death after discharge: Data from the Korean Acute Heart Failure (KorAHF) registry

BACKGROUND

Identifying patients with acute heart failure (HF) at high risk for readmission or death after hospital discharge will enable the optimization of treatment and management. The objective of this study was to develop a risk score for 30-day HF-specific readmission or death in Korea.

METHODS

We analyzed the data from the Korean Acute Heart Failure (KorAHF) registry to develop a risk score. The model was derived from a multiple logistic regression analysis using a stepwise variable selection method. We also proposed a point-based risk score to predict the risk of 30-day HF-specific readmission or death by simply summing the scores assigned to each risk variable. Model performance was assessed using an area under the receiver operating characteristic curve (AUC), the Hosmer-Lemeshow goodness-of-fit test, the net reclassification improvement (NRI), and the integrated discrimination improvement (IDI) index to evaluate discrimination, calibration, and reclassification, respectively.

RESULTS

Data from 4566 patients aged ≥40 years were included in the analysis. Among them, 446 (9.8%) had 30-day HF-specific readmission or death. The final model included 12 independent variables (age, New York Heart Association functional class, clinical history of hypertension, HF admission, chronic obstructive pulmonary disease, etiology of cardiomyopathy, systolic blood pressure, left ventricular ejection fraction, serum sodium, brain natriuretic peptide, N-terminal prohormone of brain natriuretic peptide at discharge, and prescription of β-blockers and angiotensin-converting enzyme inhibitors or angiotensin II receptor antagonists at discharge). The point risk score showed moderate discrimination (AUC of 0.710; 95% confidence interval, 0.685-0.735) and good calibration (χ²=8.540, p=0.3826).

CONCLUSIONS

The risk score for the prediction of the risk of 30-day HF-specific readmission or death after hospital discharge was developed using 12 predictors. It can be utilized to guide appropriate interventions or care strategies for patients with HF.

The product of fasting plasma glucose and triglycerides improves risk prediction of type 2 diabetes in middle-aged Koreans

BACKGROUND

Screening for risk of type 2 diabetes mellitus (T2DM) is an important public health issue. Previous studies report that fasting plasma glucose (FPG) and triglyceride (TG)-related indices, such as lipid accumulation product (LAP) and the product of fasting glucose and triglyceride (TyG index), are associated with incident T2DM. We aimed to evaluate whether FPG or TG-related indices can improve the predictive ability of a diabetes risk model for middle-aged Koreans.

METHODS

7708 Koreans aged 40-69 years without diabetes at baseline were eligible from the Korean Genome and Epidemiology Study. The overall cumulative incidence of T2DM was 21.1% (766 cases) in men and 19.6% (797 cases) in women. Therefore, the overall cumulative incidence of T2DM was 20.3% (1563 cases). Multiple logistic regression analysis was conducted to compare the odds ratios (ORs) for incident T2DM for each index. The area under the receiver operating characteristic curve (AROC), continuous net reclassification improvement (cNRI), and integrated discrimination improvement (IDI) were calculated when each measure was added to the basic risk model for diabetes.

RESULTS

All the TG-related indices and FPG were more strongly associated with incident T2DM than WC in our study population. The adjusted ORs for the highest quartiles of WC, TG, FPG, LAP, and TyG index compared to the lowest, were 1.64 (95% CI, 1.13-2.38), 2.03 (1.59-2.61), 3.85 (2.99-4.97), 2.47 (1.82-3.34), and 2.79 (2.16-3.60) in men, and 1.17 (0.83-1.65), 2.42 (1.90-3.08), 2.15 (1.71-2.71), 2.44 (1.82-3.26), and 2.85 (2.22-3.66) in women, respectively. The addition of TG-related parameters or FPG, but not WC, to the basic risk model for T2DM (including age, body mass index, family history of diabetes, hypertension, current smoking, current drinking, and regular exercise) significantly increased cNRI, IDI, and AROC in both sexes.

CONCLUSIONS

Adding either TyG index or FPG into the basic risk model for T2DM increases its prediction and reclassification ability. Compared to FPG, TyG index was a more robust T2DM predictor in the stratified sex and fasting glucose level. Therefore, TyG index should be considered as a screening tool for identification of people at high risk for T2DM in practice.

Trend of Prevalence of Atrial Fibrillation and use of Oral Anticoagulation Therapy in Patients With Atrial Fibrillation in South Korea (2002-2013)

BACKGROUND

This study examined the annual prevalence of atrial fibrillation (AF) and its associated comorbidities, as well as the prevalence of warfarin therapy in South Korean patients with AF.

METHODS

The National Health Insurance Service-National Sample Cohort database was searched for subjects aged ≥30 years diagnosed with AF from 2002-2013. The prevalence of AF was analyzed by sex and age, as was the current status of warfarin therapy in AF patients according to CHA₂DS₂-VASc score and comorbidities.

RESULTS

The age-standardized prevalence of AF in men and women was 0.15% and 0.14%, respectively, in 2002, increasing to 0.54% and 0.39%, respectively, in 2013. In 2013, the prevalence of AF in men and women aged 30-39 years was 0.08% and 0.03%, respectively, increasing to 2.35% and 1.71%, respectively, in those in aged ≥60 years. During 2002-2013, the prevalence of AF in men significantly increased among subjects aged ≥30 years and increased in women aged ≥60 years. The age-standardized prevalence of hypertension and diabetes mellitus among AF patients were markedly increased during 2002-2013. Of these AF patients, 86.1% had a CHA₂DS₂-VASc score of ≥2; however, only 39.1% of these were receiving warfarin.

CONCLUSIONS

The age-standardized prevalence of AF increased 2.89-fold over the 12-year study period. The total number of patients with AF in South Korea has been drastically increasing, due to not only aging society but also increasing age-specific prevalence of AF, especially in middle-aged and elderly individuals. The rate of warfarin therapy increased slightly over the study period but remains low.

Epidemiology of Heart Failure in Korea: Present and Future

Background and Objectives

Heart failure (HF) is an important healthcare issue because of its high mortality, morbidity, and healthcare costs. The number of HF patients is increasing worldwide as a consequence of aging of the population. However, there are limited studies on the prevalence of HF in Korea. This study aimed to estimate the prevalence of HF, its comorbidities, and the projected population with HF in the future.

Materials and Methods

The prevalence and comorbidity estimates of HF were determined using data from the 2002-2013 National Sample Cohort based on the National Health Information Database. We calculated the projected prevalence of HF by multiplying the estimated prevalence in 2013 by the projected population counts for 2015-2040.

Results

The prevalence of HF in Korea was estimated to be 1.53% in 2013. The prevalence of HF in Korea is expected to increase by 2-fold, from 1.60% in 2015 to 3.35% in 2040. By 2040, more than 1.7 million Koreans are expected to have HF. In terms of comorbid diseases of HF, ischemic heart disease, hypertension, and diabetes mellitus were common (45.4%, 43.6%, and 49.1% in 2013, respectively). The prevalence rates of arrhythmia, valvular disease, and cardiomyopathy in HF patients were approximately 22.6%, 5.6%, and 3.1% in 2013, respectively.

Conclusion

This is the first nationwide report in Korea to demonstrate the prevalence and comorbidities of HF. These data may be used for the prevention and management of HF in Korea.

Incidence and Risk Factors for Atrial Fibrillation in Korea: the National Health Insurance Service Database (2002-2010)

BACKGROUND AND OBJECTIVES

Atrial fibrillation (AF) is a common arrhythmia that is known as an important independent risk factor for stroke. However, limited information is available on AF in Korea. This study evaluated the incidence of AF, its associated co-morbidities and risk factors for AF in Korea.

SUBJECTS AND METHODS

The National Health Insurance Service database between 2002 and 2010 was used in the study. Individuals<30 years old and those diagnosed with AF between 2002 and 2004 were excluded. Hazard ratios (HRs) according to co-morbidities and risk factors for AF were determined using a Cox proportional hazard model. Population attributable fractions (PAFs) of AF risk factors were determined.

RESULTS

During a 6-year follow-up period, 3517 (1.7%) developed AF. The incidence rates in men and women aged 30-39 years were 0.82 and 0.55 per 1000 person-years, respectively; the incidence rates further increased with age to 13.09 and 11.54 per 1000 person-years in men and women aged≥80 years, respectively. The risk factors for incident AF were age, sex, body mass index (BMI), hypertension, ischemic heart disease (IHD) and heart failure. After adjusting for variables related to AF, the risk of AF was significantly associated with hypertension (HR 1.667), IHD (HR 1.639), heart failure (HR 1.521), and the PAFs for age, sex, BMI, hypertension, IHD, heart failure and diabetes mellitus were 30.6%, 10.1%, 3.4%, 16.6%, 8.2%, 5.3% and 0.8%, respectively.

CONCLUSION

Incidence of AF increased with age and was higher in men than in women. A larger proportion of AF events was attributable to hypertension than to other co-morbidities.

Validation of the Korean Genome Epidemiology Study Risk Score to Predict Incident Hypertension in a Large Nationwide Korean Cohort

BACKGROUND

This study aimed to validate the Korean Genome Epidemiology Study (KoGES) risk score to predict the 4-year risk of hypertension (HT) in a large nationwide sample, and compare its discrimination and calibration with the Framingham and blood pressure (BP)-only models.

METHODS AND RESULTS

This study analyzed 69,918 subjects without HT at baseline from the National Sample Cohort in the National Health Insurance Service database. We compared the Framingham, KoGES, and BP-only models for discrimination using area under the receiver-operating characteristic curves (AROC), calibration using goodness-of-fit tests, and reclassification ability using the continuous net reclassification improvement (NRI) and integrated discrimination improvement. Of 69,918 subjects, 18.6% developed HT during the follow-up. AROC was significantly higher for the KoGES (0.733) than for the Framingham (0.729) or BP-only (0.707) model. Recalibrated Framingham model underestimated HT incidence in all deciles (P<0.001). BP-only model overestimated risk in the lower deciles (P<0.001). KoGES model accurately predicted risk in all except the highest decile (χ(2)=14.85, P=0.062). The KoGES model led to a significant improvement in risk reclassification compared with the Framingham and BP-only models (NRI, 0.354; 95% confidence interval [CI], 0.343-0.365 and 0.542; 95% CI, 0.523-0.561, respectively).

CONCLUSIONS

In this validation study, the KoGES model demonstrated better discrimination, calibration, and reclassification ability than either the Framingham or BP-only model. The KoGES model may help identify Korean individuals at high risk for HT. (Circ J 2016; 80: 1578-1582).

Review of the Registration in the Clinical Research Information Service

Clinical research registration is required in many countries to improve transparency of clinical research and to ensure subject safety. Developed in February 2010, the Clinical Research Information Service (CRIS) is an online registration system for clinical studies in Korea and one of the primary registries of the World Health Organization (WHO) International Clinical Trials Registry Platform. The present analysis investigated the characteristics of studies registered in the CRIS between February 2010 and December 2014. Data for the analysis were extracted from the CRIS database. As of December 31, 2014, 1,323 clinical studies were registered. Of these, 938 (70.9%) were interventional studies and 385 (29.1%) were observational studies. A total of 248 (18.7%) studies were funded by government sources, 1,051 (79.4%) by non-government sources, and 24 (1.8%) by both. The most frequently studied disease category based on the ICD-10 classification was the digestive system (13.1%), followed by the nervous system (9.4%) and musculoskeletal system (9.1%). Only 17.8% of the studies were registered prior to enrollment of the first subject. Comparing the number of registered or approved clinical studies between the CRIS, the Ministry of Food and Drug Safety, and ClinicalTrials.gov suggests that a considerable number of clinical studies are not registered with the CRIS; therefore, we would suggest that such registration should be the mandatory legal requirement.

Gender differences in the association between socioeconomic status and hypertension incidence: the Korean Genome and Epidemiology Study (KoGES)

Background

Hypertension is a leading cause of cardiovascular events. We examined whether there was a gender difference in the association between SES, measured by education and income, and hypertension incidence.

Methods

Data for 2596 men and 2686 women aged 40–69 years without hypertension at baseline from the Korean Genome and Epidemiology Study (KoGES) were analyzed. Participants had two follow-up examinations during 4 years, and were classified into three categories by self-reported educational attainment: ≥ 10 years, 7–9 years, and 0–6 years, and monthly household income (×10,000 Korean Won): ≥ 200, 100–199, and <100. The association between SES and incidence hypertension was examined by Cox’s proportional hazard regression analyses.

Results

Adjusting for conventional risk factors, compared with the high education group (reference), the hazard ratios (95 % confidence interval) for incident hypertension across the education categories were 1.54 (1.16–2.06) and 1.80 (1.36–2.38) in women and 1.15 (0.92–1.43), and 1.08 (0.84–1.38) in men. Women with the low household income were more likely to have hypertension than those with the high household income and incident hypertension had an inverse association with household income level in women: multivariate adjusted hazard ratios were 1.00 (reference), 1.10 (0.83–1.45), and 1.63 (0.75–2.16). Men with medium income were less likely to have hypertension compared with those with high income (0.76, 0.61–0.90).

Conclusions

Educational level and economic status had stronger impacts on hypertension in Korean women than men. Thus, a stratified approach for women of low socioeconomic status, especially those with low educational attainment, is needed for the prevention of hypertension.

Difference in blood pressure between early and late menopausal transition was significant in healthy Korean women

Background

Although the prevalence of hypertension is higher in postmenopausal women than in premenopausal women, little is known about changes in blood pressure (BP) during the menopausal transition. We evaluated BP according to the menopausal transition and associated factors in healthy Korean women.

Methods

This cross-sectional study involved 2037 women aged 44 to 56 years who presented at a health-screening center in Seoul, Korea, from November 2012 to March 2013. The association between BP and menopausal transition and the risk factors related to elevated BP were determined using multiple linear regression analyses. Menopausal status was divided by four groups as premenopause, early menopausal transition, late menopausal transition and postmenopause.

Results

Both systolic and diastolic blood pressure (SBP and DBP) differed significantly according to the menopausal status. BP showed the greatest difference between early and late menopausal transition. After adjusting for variables related to hypertension, SBP (β = 2.753, p < 0.01) and DBP (β = 1.746, p = 0.02) were significantly higher in late than early menopausal transition. The prevalence of hypertension was significantly different between early and late menopausal transition (1.4 vs. 6.1 %). Waist circumference, glucose, and triglycerides were positively and significantly associated with SBP and DBP during menopause.

Conclusions

BP and the prevalence of hypertension were significantly associated with period between early and late menopausal transition, suggesting that changes in BP during the menopausal transition are significant. Therefore, frequent monitoring will be needed for early detection of hypertension during the menopausal transition.

Electronic supplementary material

The online version of this article (doi:10.1186/s12905-015-0219-9) contains supplementary material, which is available to authorized users.

The Role of Genetic Risk Score in Predicting the Risk of Hypertension in the Korean population: Korean Genome and Epidemiology Study

Hypertension is regarded as a multifactorial disease with a modest contribution of genetic factors and strongly affected by environmental factors. Recent genome-wide association studies have identified specific loci associated with high blood pressure (BP) and hypertension. This study aimed to examine the association between the genetic risk score (GRS), a linear function of multiple single nucleotide polymorphisms (SNPs) associated with hypertension, and high BP and prevalent hypertension at baseline examination and to evaluate the efficacy of the GRS for predicting incident hypertension with longitudinal data in Korean subjects. Data for 8,556 participants, aged 40 to 69, in a community-based cohort study were analyzed. Unweighted GRS (cGRS) and weighted GRS (wGRS) were constructed from 4 SNPs related to high BP or hypertension in previous genome-wide association and its replication studies for the Korean middle-aged population. Cross-sectional analysis (n=8,556) revealed that cGRS was significantly associated with prevalent hypertension (odds ratio=1.15 per risk allele; 95%CI, 1.09-1.20). Additionally, the odds ratios (ORs) of prevalent hypertension for those who in medium and the highest tertile compared with those who in the lowest tertile of wGRS were 1.31 (95% CI, 1.15-1.50) and 1.59 (95%CI, 1.38-1.82), respectively. In a longitudinal analysis (n=5,632), participants in the highest tertile of wGRS had a 1.22-fold (OR=1.22, 95%CI, 1.02‒1.46) greater risk of incident hypertension relative to those in the lowest tertile, after adjusting for a number of confounding factors. However, wGRS topped with traditional risk factors had no significant effect on discrimination ability (c-statistics with and without wGRS were 0.811 and 0.810, P=0.1057). But, reclassification analysis showed that the addition of GRS to the model with conventional risk factors led to about 9% significant increment in category-free net reclassification improvement. GRSs based on 4 SNPs were independently associated with hypertension and may provide a statistically significant improvement over the existing model for prediction of incident hypertension.

Impaired fasting glucose and impaired glucose tolerance do not predict hypertension: a community cohort study

BACKGROUND

Insulin resistance has an important role in the pathogenesis of hypertension. We hypothesized that impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) which represents insulin resistance would predict the development of hypertension.

METHODS

A total of 4,039 subjects without hypertension or diabetes (1,847 men and 2,192 women; age 49.9±8.2 years), from the Ansan-Ansung cohorts within the Korean Genome Epidemiology Study, were enrolled in 2001-2002 and restudied in 2005-2006. The association between the incidence of hypertension and IFG, IGT, or other metabolic factors was studied.

RESULTS

During the 4-year follow-up period, 582 of the 4,039 subjects developed hypertension. At baseline, the prevalence of abdominal obesity, dyslipidemia, and IGT was higher in subjects who became hypertensive compared to those that remained normotensive. The prevalence of IFG was not significantly different between the 2 groups. In a multivariate analysis, abdominal obesity and high serum triglyceride were significant risk factors for the development of hypertension. Neither IFG nor IGT were significantly associated with new-onset hypertension. Although the risk of hypertension was higher with the number of metabolic components present at baseline, IFG and IGT were not significant components compared to other metabolic components, especially when abdominal obesity was taken into account.

CONCLUSIONS

While metabolic syndrome components related to insulin resistance present at baseline are important risk factors of hypertension, we conclude that coexisting metabolic component, mainly abdominal obesity, rather than IFG and IGT have more predictive value for determining the development of hypertension in a Korean population.

Anthropometric indices as predictors of hypertension among men and women aged 40-69 years in the Korean population: the Korean Genome and Epidemiology Study

Background

Obesity is one of the most significant risk factors for hypertension. However, there is controversy regarding which measure is the best predictor of hypertension risk. We compared body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) in subjects as predictive indicators for development of hypertension.

Methods

The data were obtained from the Korean Genome and Epidemiology Study (KoGES), a large population-based prospective cohort study. A total of 4,454 subjects (2,128 men and 2,326 women) aged 40–69 years who did not have hypertension at baseline were included in this study. Incident hypertension was defined as systolic blood pressure ≥140 mmHg, diastolic blood pressure ≥90 mmHg, or anti-hypertensive medication use during the 4-year follow up. Receiver operating characteristic (ROC) analysis was used to compare discrimination abilities for anthropometric indices for hypertension. Hazard ratios were calculated by Cox proportional hazard model with adjustment for age, smoking status, alcohol consumption, diabetes and family history of hypertension by sexes.

Results

In men, the area under the ROC curve (AROC) was 0.62 for WC, WHR, and WHtR and 0.58 for BMI. In women, the AROCs for BMI, WC, WHR, and WHtR were 0.57, 0.66, 0.68, and 0.68, respectively. After adjustment for risk factors, a 1 standard deviation increase in BMI, WC, WHR, WHtR were significantly related to incident hypertension, respectively (hazard ratio: 1.39, 1.50, 1.40 and 1.49 in men, 1.31, 1.44, 1.35 and 1.48 in women).

Conclusions

The central obesity indices WC, WHR, and WHtR were better than BMI for the prediction of hypertension in middle-aged Korean people. WHtR facilitates prediction of incident hypertension because of the single standard regardless of sex, ethnicity, and age group. Therefore, WHtR is recommended as a screening tool for the prediction of hypertension.

Predicting the risk of incident hypertension in a Korean middle-aged population: Korean genome and epidemiology study

The objectives of this study were to construct a risk score for predicting incident hypertension by using the Korean Genome and Epidemiology Study (KoGES) data and to compare the performance between KoGES and the Framingham model. A total of 4747 participants were analyzed. The entire cohort was randomly assigned to derivation and validation sets at a ratio of 6:4. A hypertension risk score was developed based on the derivation cohort, using the same risk factors that were used for developing the Framingham hypertension risk score. The accuracy of KoGES and Framingham models was evaluated in terms of calibration and discrimination. The area under receiver operating characteristic (AROC) curves were 0.789 for the Framingham model and 0.791 for the KoGES model. The AROC calculated for the point-based risk score was 0.790, which is almost identical to that for the KoGES model. The Framingham model showed poor agreement (χ(2) =29.73, P=.0002) and underestimated the risk of hypertension in most deciles of predicted risk. The model based on KoGES yielded results similar to the observed risk of hypertension (χ(2) =4.17, P=.8415). This study demonstrates that the Framingham risk score based on data from a non-Korean population can lead to the underestimation of the prediction risk of hypertension.

Relationship between prehypertension and chronic kidney disease in middle-aged people in Korea: the Korean genome and epidemiology study

Background

Elevated blood pressure (BP) is a major risk factor for the progression of chronic kidney disease (CKD). However, little is known about the influence of prehypertension on CKD. In this study, we investigated the relationship between prehypertension and CKD in a middle-aged Korean population. Furthermore, we prospectively evaluated the effect of active BP control on deterioration of kidney function during the two-year follow-up.

Methods

The Korean Genome and Epidemiology Study is a community-based prospective cohort study started in 2001, with a follow-up survey conducted every two years. A total of 9509 participants aged 40–69 years were included in a baseline study. BP was classified according to the Seventh Report of the Joint National Committee on High BP (JNC-7) categories and CKD was defined as the presence of proteinuria or eGFR< 60mL/min/1.73m². A multivariable logistic regression model was used to identify associations between BP and CKD.

Results

The overall prevalence of CKD was 13.2%, and significantly increased with BP level. The multivariable-adjusted odds ratio of CKD was 1.59 for prehypertension and 2.27 for hypertension, compared with a normal BP. At the two-year follow-up, among the participants with prehypertension, subjects whose BP was poorly controlled had a significantly higher risk of eGFR drop (OR, 1.37; 95% CI, 1.13-1.67), as compared to controls. The prevalence of eGFR drop was 57.8% in the controlled BP group and 66.0% in the poorly-controlled BP group.

Conclusions

Prehypertension, as well as hypertension, is significantly associated with CKD among middle-aged Koreans. Our results indicate that active control of the blood-pressure of prehypertensive individuals is needed to prevent deterioration of kidney function.

Bioequivalence trials with the incomplete 3 x 3 crossover design

In bioequivalence trials, one often considers two or more generic products with the original one. The 3 x 3 crossover design can be adopted to evaluate the two generic candidates with a brand name drug, rather than conducting two separate 2 x 2 crossover trials. Dropouts, however, are more likely to occur due to various administrative reasons when we consider a higher order crossover design. A modified method, which was originally given by Chow and Shao (1997), is extended to compare two generic products with a reference in the incomplete 3 x 3 crossover design. A simulation study and discussion are also presented.

Crystal structure of the trimeric alpha-helical coiled-coil and the three lectin domains of human lung surfactant protein D

BACKGROUND

Human lung surfactant protein D (hSP-D) belongs to the collectin family of C-type lectins and participates in the innate immune surveillance against microorganisms in the lung through recognition of carbohydrate ligands present on the surface of pathogens. The involvement of this protein in innate immunity and the allergic response make it the subject of much interest.

RESULTS

We have determined the crystal structure of a trimeric fragment of hSP-D at 2.3 A resolution. The structure comprises an alpha-helical coiled-coil and three carbohydrate-recognition domains (CRDs). An interesting deviation from symmetry was found in the projection of a single tyrosine sidechain into the centre of the coiled-coil; the asymmetry of this residue influences the orientation of one of the adjacent CRDs. The cleft between the three CRDs presents a large positively charged surface.

CONCLUSIONS

The fold of the CRD of hSP-D is similar to that of the mannan-binding protein (MBP), but its orientation relative to the alpha-helical coiled-coil region differs somewhat to that seen in the MBP structure. The novel central packing of the tyrosine sidechain within the coiled-coil and the resulting asymmetric orientation of the CRDs has unexpected functional implications. The positively charged surface might facilitate binding to negatively charged structures, such as lipopolysaccharides.

A study of the xenogeneic response in an isolated liver perfusion circuit--preliminary observations

An isolated liver perfusion circuit was developed to study the xenogeneic reaction of human blood to porcine liver, and investigate the feasibility of using such a system for liver dialysis in fulminant hepatic failure. Three experimental groups were studied: a control group where pooled porcine blood was perfused through pig liver (n = 12), a xenogeneic group where banked human blood was perfused through porcine liver (n = 23), and a modified xenogeneic group where decomplemented human blood was perfused through porcine liver (n = 4). The following parameters of liver function were assessed: liver function tests, serum electrolytes, bile and ascites production. In addition, liver histology was assessed at the start and completion of each perfusion experiment. Control experiments established that the use of low perfusion pressures (mean inlet pressure of 29.5 +/- 7.4 mmHg), and low haematocrit of 20.5 +/- 8.9% (n = 14), enabled five hour perfusions to be consistently achieved with maintenance of normal acid base and electrolyte balance. Bile production over 5 hours was 18.8 +/- 8.0 ml in controls (n = 5) and 17.0 +/- 6.7 ml in the xenogeneic (human-pig) circuit (n = 11) (NS). Ascites production was 235.8 +/- 157.3 ml/hr in controls (n = 5) and 205 +/- 142.0 ml/hr in the xenogeneic circuit (n = 7) (NS).(ABSTRACT TRUNCATED AT 250 WORDS)

An in vitro assessment of human fetal pancreatic islets of Langerhans in culture

The human fetal pancreas is a potential source of islets for transplantation into insulin-dependent diabetic patients. In this study, 35 human fetal pancreas obtained from prostaglandin-induced abortions (12-26 weeks gestation), were placed in culture to determine their capacity to secrete insulin over 30 days. Culture media were sampled twice weekly for insulin and histology was performed serially. Of the 35 pancreases cultured, six were lost due to bacterial contamination, five discarded due to undetectable levels of insulin in culture, nine are still under study, whilst 15 pancreases have been cultured for one month, and insulin studies completed. Three patterns of insulin release were observed: (a) progressive decline (n = 6), indicating non-viable tissue at the onset; (b) delayed decline, indicating significant tissue damage before organ culture (n = 5); and (c) insulin production in vitro over 30 days (n = 4), with viable islets detected histologically. Factors such as gestational age and cold ischaemia time did not correlate with the pattern of insulin secretion observed. This was probably due to a more important variable, not easily assessed, of the period of intrauterine (warm) ischemia. These data suggest: (1) that a small number of fetal pancreases procured from prostaglandin-induced abortuses do yield islets which remain viable in culture over 30 days, and (2) the functional status of islets can be monitored in vivo by measuring insulin secretion, thereby providing a means of identifying tissue suitable for transplantation.

Fetal pig pancreas--a preliminary assessment of tissue for transplantation

Porcine fetal pancreases (PFP) obtained from 4 pregnant sows were pooled, minced into 1 mm3 fragments and studied in organ culture for up to 30 days to determine tissue viability and insulin production in vitro. After 7-9 days in culture, some of these explants were transplanted into euglycemic, N:NIH-nu(s) nude recipient mice, and studied histologically over 69 days following grafting. Using RPMI 1640 supplemented with 5% fetal calf serum as the culture medium in 90% air/10% CO2, it was found that explants were viable with insulin production detected in vitro, which was maximal at day 7 (197 +/- 18.9 mU/L, n = 11), and gradually declined thereafter. By 22 days, insulin levels were less than 60.1 +/- 28.5 mU/L (n = 6). Histology of the explants showed viable tissue with evidence of mitoses present in insulin-positive cells at day 16 in vitro. Beyond this time, tissue viability diminished. Explants transplanted into euglycemic nude mice did not undergo rejection during the observation period of 69 days. Grafts remained viable with evidence of an increase in mitotic activity in the endocrine tissue on immunoperoxidase staining. These preliminary investigations confirm that pancreatic explants from porcine fetuses can be maintained in culture for up to 16 days. Such explants, when transplanted under the kidney capsule of euglycemic, nude mice, did not undergo necrosis, but remained viable, with evidence of mitoses in the islet tissue.