Modification of the association between cold spells and cardiovascular disease by changes in natural gas prices: A nationwide time-series study.

BACKGROUND: Although the association between low ambient temperature and cardiovascular disease (CVD) is well-established, the effect of winter energy prices on this association remains unknown. AIM: This ecological study aimed to investigate whether changes in natural gas prices (NGP), which account for a significant portion of winter energy prices in Korea, affect the association of cold spells with hospital admissions and mortality due to CVD. METHODS: Data from the National Health Insurance Service and Statistics Korea were used to determine the daily number of hospital admissions and mortality rates associated with CVD. From January 2012 to February 2017, the NGP continually increased by 24.1%. From January 2012 to December 2014 the NGP continually decreased by 32.6% owing to the Korea Gas Corporation's management decisions, independent of external socioeconomic factors. We investigated the differences in the associations between cold spells and CVD-related outcomes in price-increasing and price-decreasing periods using a Poisson regression with a distributed lag nonlinear model. Cold spells were assessed on two consecutive days at the 5th percentile of the temperature for each region. RESULTS: The meteorological factors and air pollution levels were similar between the two periods. The association between cold spells and hospital admissions due to CVD was stronger during the price-increasing period than during the price-decreasing period [ratio of cumulative relative risk (RRR) = 1.71, 95% confidence interval (CI): 1.31-2.22]. The difference in the association with mortality due to CVD between the two periods was not significant, although the point estimate remained >1 (RRR = 1.11, 95% CI: 0.90-1.38). CONCLUSIONS: Changes in energy prices may modify the cold spell-related CVD risk, possibly by inducing behavioral changes to manage energy expenditure. Policymakers should take into account the potential public health implications of changes in energy prices, alongside their economic effects.

Prenatal and childhood exposure to endocrine-disrupting chemicals and early thelarche in 8-year-old girls: A prospective study using Bayesian kernel regression.

BACKGROUND: Studies on the combined effects of persistent and non-persistent endocrine-disrupting chemicals (EDCs) on puberty are insufficient. To date, no studies have analyzed breast development at age 8 years, a key criterion for determining precocious puberty. We investigated the relationship between prenatal or childhood exposure to EDC mixtures and early thelarche, defined as breast development before age 8 years in girls. METHODS: This prospective study included 211 girls with data on prenatal and 8-year-old exposure of cadmium (Cd), lead, mercury, bisphenol-A (BPA), 3-phenoxybenzoic acid, and three phthalate metabolites from the Environment and Development of Children cohort. Prenatal exposure was assessed through samples from pregnant women at 14-27th weeks of gestation. Tanner staging was assessed by a pediatric endocrinologist. The relationship between single and mixed chemical exposures and outcomes was assessed using logistic regression, generalized additive models (GAM), and Bayesian kernel machine regression (BKMR) models. RESULTS: Early thelarche was observed in 42 (19.9%) girls at age 8 years. In the logistic regression models, the risk of early thelarche increased with increased exposure to Cd in their mothers (adjusted odds ratio [aOR] per interquartile range [IQR]=1.80, 95% confidence interval [CI] 1.23-2.65) but decreased with prenatal BPA exposure (aOR per IQR=0.57, 95% CI 0.35-0.92). None of the 8-year-old chemical exposures was associated with early thelarche. In the GAM, early thelarche was positively correlated with prenatal Cd and inversely associated with prenatal BPA exposure (p=0.004 for Cd and p=0.036 for BPA). In the BKMR models, an increase in log-transformed prenatal Cd concentrations from the 25th to 75th percentile was associated with an increase in the estimated probability of early thelarche at age 8 years (risk difference: 0.46 [95% credible interval: 0.04-0.88]) when other chemicals were set at their median values. CONCLUSIONS: Considering the combined effects of persistent and non-persistent chemical mixtures, maternal Cd exposure during the second trimester may be associated with early thelarche in 8-year-old girls.

Associations between short-term exposure to air pollution and thyroid function in a representative sample of the Korean population.

BACKGROUND: Disruption of thyroid function can profoundly affect various organ systems. However, studies on the association between air pollution and thyroid function are relatively scarce and most studies have focused on the long-term effects of air pollution among pregnant women. OBJECTIVES: This study aimed to explore the associations between short-term exposure to air pollution and thyroid function in the general population. METHODS: Data from the Korea National Health and Nutrition Examination Survey (2013-2015) were analyzed (n = 5,626). Air pollution concentrations in residential addresses were estimated using Community Multiscale Air Quality models. The moving averages of air pollution over 7 days were set as exposure variables through exploratory analyses. Linear regression and quantile g-computation models were constructed to assess the effects of individual air pollutants and air pollution mixture, respectively. RESULTS: A 10-ppb increase in NO2 (18.8-µg/m3 increase) and CO (11.5-µg/m3 increase) was associated with 2.43% [95% confidence interval (CI): 0.42, 4.48] and 0.19% (95% CI: 0.01, 0.36) higher thyroid-stimulating hormone (TSH) levels, respectively. A 10-µg/m3 increase in PM2.5 and a 10-ppb increase in O3 (19.6-µg/m3 increment) were associated with 0.87% (95% CI: 1.47, -0.27) and 0.59% (95% CI: 1.18, -0.001) lower free thyroxine (fT4) levels, respectively. A simultaneous quartile increase in PM2.5, NO2, O3, and CO levels was associated with lower fT4 but not TSH levels. CONCLUSIONS: As the subtle changes in thyroid function can affect various organ systems, the present results may have substantial public health implications despite the relatively modest effect sizes. Because this was a cross-sectional study, it is necessary to conduct further experimental or repeated-measures studies to consolidate the current results.

Association Between Instant Coffee Consumption and the Development of Chronic Obstructive Pulmonary Disease: Results From a Community-Based Prospective Cohort.

BACKGROUND: A poor diet is a risk factor for chronic obstructive pulmonary disease (COPD). The interaction between dietary factors and cigarette smoking in the development of COPD is unclear. We investigated the interactions between dietary patterns and smoking status on COPD-related outcomes. METHODS: We used data from the Anseong-Ansan cohort that has been followed for 20 years. A total of 6,221 individuals without COPD in the baseline survey were analyzed. Five dietary patterns were identified using a semi-quantitative food frequency questionnaire. Associations of dietary patterns with COPD and forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) ratio in different strata of smoking status were evaluated using Cox regression and linear mixed models, respectively. RESULTS: The highest quartile of the "coffee" pattern (high coffee consumption) was associated with COPD (hazard ratio, 1.46; 95% confidence interval [CI], 1.03-2.08) and lower FEV1/FVC ratio (ß = -1.2%; 95% CI, -1.9% to -0.6%) using the lowest quartile as a reference for heavy smokers, but not light or never smokers (P value for interaction = 0.035 for COPD). Regarding the associations between various consumption levels of black coffee, combined coffee, and instant coffee and COPD, an association with COPD was only observed for instant coffee in heavy smokers. CONCLUSION: High instant coffee consumption is associated with COPD development in heavy smokers, but not in light or never smokers. This may be attributed to sugar and cream in instant coffee mixes.

Association Between Eight Autoimmune Diseases and Thyroid Cancer: A Nationwide Cohort Study.

Background: It has often been reported that thyroid-specific autoimmune diseases (ADs), such as Hashimoto's thyroiditis and Graves' disease, could increase the risk of thyroid cancer, but the association between other ADs beyond thyroid and thyroid cancer has not been well investigated. This study aimed to examine the risk of thyroid cancer in patients with eight ADs compared with those without ADs. Methods: This nationwide retrospective matched cohort study was conducted to investigate the relationship of eight ADs (Hashimoto's thyroiditis, Graves' disease, type 1 diabetes mellitus, Sjogren's disease, inflammatory bowel disease [IBD], vitiligo, systemic lupus erythematosus, and rheumatoid arthritis [RA]) with the risk of incident thyroid cancer using the National Health Insurance Service-National Sample Cohort. The Cox-proportional hazard model was used to estimate the adjusted hazard ratio (HR) and confidence intervals (CI) for thyroid cancer in relation to each of AD compared with control group without AD. Results: During the average follow-up of 9.49 years, 138 thyroid cancer cases were newly developed in control group and 268 cases were occurred in group with 8 ADs. For all of study participants, the risk of thyroid cancer was significantly increased in patients with Hashimoto's thyroiditis (HR = 2.10 [1.57-2.81]), Graves' disease (HR = 2.67 [1.99-3.62]), IBD (HR = 2.06 [1.50-2.83]), vitiligo (HR = 1.71 [1.13-2.59]), RA (HR = 1.76 [1.07-2.90]), and total of 8 ADs (HR = 1.97 [1.60-2.42]) compared with control group without ADs. When ADs were divided into three types, thyroid-specific ADs (HR = 2.37 [1.85-3.03]) showed the strongest and significant association with thyroid cancer, followed by local ADs (HR = 1.83 [1.41-2.38]), and systemic ADs (HR = 1.77 [1.14-2.74]). Conclusions: Specific ADs-especially for thyroid-specific AD, vitiligo, IBD, and RA-were associated with increased risk for thyroid cancer.

Association of Infant Feeding Characteristics With Dietary Patterns and Obesity in Korean Childhood.

OBJECTIVES: Young children's feeding characteristics can play an important role in eating habits and health during later childhood. This study was conducted to examine the associations of feeding characteristics with dietary patterns and obesity in children. METHODS: This study utilized data from the Korea National Health and Nutrition Examination Survey conducted between 2013 and 2017. In total, 802 toddlers were included, with information on their demographic characteristics, feeding practices and duration, and 24-hour recall obtained from their parents. Feeding characteristics were categorized into feeding type, duration of total breastfeeding, duration of total formula feeding, duration of exclusive breastfeeding, and age when starting formula feeding. Dietary patterns were identified based on factor loadings for the food groups for 3 major factors, with "vegetables & traditional," "fish & carbohydrates," and "sweet & fat" patterns. Overweight/obesity was defined as ≥85th percentile in body mass index based on the 2017 Korean National Growth charts for children and adolescents. Multiple regression analysis was conducted to examine associations between feeding characteristics and dietary patterns. The association between dietary patterns and obesity was analyzed using multivariable logistic regression analysis. RESULTS: The early introduction of formula feeding was inversely associated with the "vegetables & traditional" pattern (ß=-0.18; 95% confidence interval [CI], -0.34 to -0.02). A higher "vegetables & traditional" intake was associated with a lower risk of obesity (odds ratio, 0.48; 95% CI, 0.24 to 0.95). CONCLUSIONS: Feeding characteristics are associated with dietary patterns in later childhood, and dietary patterns were shown to have a potential protective association against obesity.

Sex-specific Associations between Body Mass Index and Thyroid Cancer Incidence among Korean Adults.

BACKGROUND: The potential differences by sex in the association between body mass index (BMI) and thyroid cancer risk remain unconfirmed. METHODS: Data from the National Health Insurance Service-National Health Screening Cohort (NHIS-HEALS; 2002-2015; population size = 510,619) and the Korean Multi-center Cancer Cohort (KMCC) data (1993-2015; population size = 19,026) were used. We constructed Cox regression models, adjusted for potential confounders, to evaluate the association between BMI and thyroid cancer incidence in each cohort, and assessed the consistency of the results. RESULTS: In the NHIS-HEALS, 1,351 and 4,609 incident thyroid cancer cases occurred during the follow-up among men and women, respectively. Compared with BMI of 18.5-22.9 kg/m2, BMI of 23.0-24.9 [no. of cases = 410; HR, 1.25; 95% confidence interval (CI), 1.08-1.44], 25.0-29.9 (no. of cases = 522; HR, 1.32; 95% CI, 1.15-1.51), and ≥30.0 kg/m2 (no. of cases = 48; HR, 1.93; 95% CI, 1.42-2.61) were associated with an increased risk of incident thyroid cancer among males. Among females, BMI of 23.0-24.9 (no. of cases = 1,300; HR, 1.17; 95% CI, 1.09-1.26) and 25.0-29.9 (no. of cases = 1,406; HR, 1.20; 95% CI, 1.11-1.29) were associated with incident thyroid cancer. The analyses using the KMCC demonstrated results consistent with wider CIs. CONCLUSIONS: Sex differences in the associations between BMI and thyroid cancer incidence were observed in Korean cohorts. IMPACT: BMI <23 kg/m2 may help prevent incident thyroid cancer, especially among men.

Use of machine learning to improve the estimation of conductivity and permittivity based on longitudinal relaxation time T1 in magnetic resonance at 7 T.

Electrical property tomography (EPT) is a noninvasive method that uses magnetic resonance imaging (MRI) to estimate the conductivity and permittivity of tissues, and hence, can be used as a biomarker. One branch of EPT is based on the correlation of water and relaxation time T1 with the conductivity and permittivity of tissues. This correlation was applied to a curve-fitting function to estimate electrical properties, it was found to have a high correlation between permittivity and T1 however the computation of conductivity based on T1 requires to estimate the water content. In this study, we developed multiple phantoms with several ingredients that modify the conductivity and permittivity and explored the use of machine learning algorithms to have a direct estimation of conductivity and permittivity based on MR images and the relaxation time T1. To train the algorithms, each phantom was measured using a dielectric measurement device to acquire the true conductivity and permittivity. MR images were taken for each phantom, and the T1 values were measured. Then, the acquired data were tested using curve fitting, regression learning, and neural fit models to estimate the conductivity and permittivity values based on the T1 values. In particular, the regression learning algorithm based on Gaussian process regression showed high accuracy with a coefficient of determination R2 of 0.96 and 0.99 for permittivity and conductivity, respectively. The estimation of permittivity using regression learning demonstrated a lower mean error of 0.66% compared to the curve fitting method, which resulted in a mean error of 3.6%. The estimation of conductivity also showed that the regression learning approach had a lower mean error of 0.49%, whereas the curve fitting method resulted in a mean error of 6%. The findings suggest that utilizing regression learning models, specifically Gaussian process regression, can result in more accurate estimations for both permittivity and conductivity compared to other methods.

Feeding characteristics in infancy affect fruit and vegetable consumption and dietary variety in early childhood.

BACKGROUND/OBJECTIVES: Previous studies have shown an association between breastfeeding and higher fruit and vegetable consumption and the level of dietary variety in children. However, few studies have reported this association on the feeding characteristics. Therefore, this study examined the association of the feeding characteristics with the consumption of fruit and vegetable and dietary variety in children. SUBJECTS/METHODS: This study recruited 802 participants from their parents with information on their feeding, and 24-h dietary recall. The associations of the feeding characteristics with fruit and vegetable consumption and dietary variety score (DVS) were analyzed using a multiple logistic regression model. RESULTS: Compared to the feeding type of exclusive breastfed children, exclusive formula-fed children had a significant association with a lower DVS (odds ratio [OR], 0.42, 95% confidence interval [CI], 0.23-0.77). Fruit and vegetable consumption was classified into 6 groups: non-salted vegetables (NSV), salted vegetables (SV), fruit (F), total vegetables (TV), non-salted vegetables + fruit (NSVF), and total vegetables + fruit (TVF). According to the mean level of fruit and vegetable consumption, compared to the duration of total breastfeeding for 6 month or less, a greater duration of breastfeeding for 12 mon had a significant association with a higher intake of NSVF and TVF (OR, 1.85, 95% CI, 1.20-2.85 and OR, 1.89, 95% CI, 1.22-2.92). On the other hand, the early introduction of formula feeding for 4 mon had a significant association with a lower intake of F and NSVF (OR, 0.59, 95% CI, 0.38-0.91 and OR, 0.63, 95% CI, 0.40-0.99). CONCLUSIONS: These results confirm that breastfeeding is associated with higher fruit and vegetable consumption and dietary variety, whereas formula feeding is associated with lower fruit and vegetable consumption and dietary variety. Therefore, the feeding characteristics in infants may affect fruit and vegetable consumption and dietary variety in children.

Association between long-term air pollution exposure and development of diabetes among community-dwelling adults: Modification of the associations by dietary nutrients.

BACKGROUND: Studies on the modifying effects of dietary factors on the association between air pollution and diabetes-related outcomes are limited. We examined whether dietary nutrients could modify the association between long-term air pollution exposure and the development of diabetes. METHODS: We used data from the Cardiovascular Disease Association Study, which enrolled adults aged 40-69 years in Korea between 2005 and 2011 and followed them up until 2016 (n = 14,667). Annual concentrations of fine particulate matter (PM2.5) and nitrogen dioxide (NO2) at each participant's residence(s) were estimated using community multiscale air quality models. Intake of 22 dietary nutrients was assessed using a validated food frequency questionnaire during the baseline survey. We examined the product terms between air pollution levels (continuous) and each dietary nutrient (quartile) using Cox regression models, adjusted for potential confounders. RESULTS: PM2.5 [hazard ratio (HR) = 1.49, 95 % confidence interval (CI): 1.11, 2.00] and NO2 (HR = 1.29, 95 % CI: 1.12, 1.49) concentrations were found to be associated with incident diabetes. NO2 levels interacted with dietary intake of retinol, vitamin A, and cholesterol (p-values for interaction < 0.05). Stronger associations were observed between NO2 levels and the occurrence of diabetes among individuals with a lower intake of these nutrients compared to those with a higher intake. No interaction was found between PM2.5 and the 22 investigated dietary nutrients. CONCLUSIONS: Adequate intake of dietary nutrients, such as retinol, vitamin A, and cholesterol, from various food items in a balanced diet may prevent the occurrence of diabetes in a setting wherein reduction of air pollution levels cannot be achieved in a short time frame.