Hypertension is an important modifiable risk factor for cardiovascular disease (CVD).¹ The population-attributable fraction of hypertension for CVD is approximately 60% in Asia.^2,3 In 2017, the American College of Cardiology/American Heart Association (ACC/AHA) released an updated guideline with a new criteria for hypertension, defining stage 1 hypertension as systolic blood pressure as 130 mm Hg through 139 mm Hg or diastolic blood pressure as 80 mm Hg through 89 mm Hg.⁴ This lower threshold for hypertension was based on multiple meta-analyses that showed higher CVD risk in the stage 1 hypertension blood pressure range.^5-11 However, most of the study populations from these studies were composed of middle-aged and elderly adults, leaving a relative lack of evidence for young adults aged 20 through 39 years.

Background: Although high serum cholesterol in young adults is known to be a predictor for cardiovascular events, there is not enough evidence for the association of cholesterol level change with cardiovascular disease ( CVD ). This study aimed to evaluate whether the change in cholesterol is associated with incidence of CVD among young adults. Methods and Results: We examined 2 682 045 young adults (aged 20–39 years) who had undergone 2 consecutive national health check‐ups provided by Korean National Health Insurance Service between 2002 and 2005. Cholesterol levels were classified into low (<180 mg/dL), middle (180–240 mg/dL) and high (≥240 mg/dL). CVD events were defined as ≥2 days hospitalization attributable to CVD for 10 years follow‐up. Increased cholesterol levels were significantly associated with elevated ischemic heart disease risk (adjusted hazard ration [ aHR ]=1.21; 95% confidence interval [ CI ]=1.03–1.42 in low‐high group and aHR =1.21; 95% CI =1.15–1.27 in middle‐high group) and cerebrovascular disease ( CEVD ) risk ( aHR =1.24; 95% CI =1.05–1.47 in low‐high group and aHR =1.09; 95% CI =1.02–1.16 in middle‐high group). Decreased cholesterol levels were associated with reduced ischemic heart disease risk ( aHR =0.91; 95% CI =0.88–0.95 in middle‐low group, aHR =0.65; 95% CI =0.56–0.75 in high‐low group and aHR =0.68; 95% CI =0.65–0.73 in high‐middle group). Furthermore, lower cerebrovascular disease risk ( aHR =0.76; 95% CI =0.62–0.92) was observed in the high‐low group compared with patients with sustained high cholesterol. Conclusions: The findings of our study indicate that increased cholesterol levels were associated with high CVD risk in young adults. Furthermore, young adults with decreased cholesterol levels had reduced risk for CVD .

Background: Anemia is thought to increase mortality risks, but the effects of high hemoglobin concentration on survival are unclear. The effect of change in hemoglobin concentrations on survival in the general population is also unknown. This study aimed to examine the effect of hemoglobin concentrations and their changes on cardiovascular and all‐cause mortality risks. Methods and Results: We retrospectively analyzed a cohort from the NHIS‐HEALS (National Health Insurance Service–National Health Screening Cohort) database, including 170 078 men and 122 116 women without cardiovascular diseases, aged >40 years at baseline, with hemoglobin concentrations available for both first and second health examinations. We assessed 2 independent variables: “One‐time” hemoglobin concentrations and changes in hemoglobin from first to second examination. Participants were followed up for a median of 8 years to determine mortality related to myocardial infarction, stroke, all cardiovascular diseases, and all causes. Hemoglobin concentrations showed a U‐ or J‐shaped association with cardiovascular and all‐cause mortality after adjusting for cardiovascular risk factors. When anemic men achieved normal hemoglobin concentrations, the all‐cause mortality risk decreased, with an adjusted hazard ratio of 0.67 (95% confidence interval, 0.59–0.77), in comparison with those whose anemia persisted. Both increases and decreases of hemoglobin concentration outside the normal range elevated all‐cause mortality risk (adjusted hazard ratio: 1.39 [95% confidence interval, 1.28–1.49] and 1.10 [95% confidence interval, 1.01–1.20], respectively), compared with persistent normal hemoglobin concentrations. The trend was similar in women but was less significant. Conclusions: Low or high hemoglobin concentrations were associated with elevated cardiovascular and all‐cause mortality. Reaching and maintaining hemoglobin concentrations within the normal range correlated with decreased all‐cause mortality.

Little is known about the trade-off between the health benefits of physical activity (PA) and the potential harmful effects of increased exposure to air pollution during outdoor PA. We examined the association of the combined effects of air pollution and changes in PA with cardiovascular disease (CVD) in young adults. This nationwide cohort study included 1 469 972 young adults aged 20–39 years. Air pollution exposure was estimated by the annual average cumulative level of particulate matter (PM). PA was calculated as minutes of metabolic equivalent tasks per week (MET-min/week) based on two consecutive health examinations from 2009 to 2012. Compared with the participants exposed to low-to-moderate levels of PM2.5 or PM10 who continuously engaged in ≥1000 MET-min/week of PA, those who decreased their PA from ≥1000 MET-min/week to 1–499 MET-min/week [PM10 adjusted hazard ratio (aHR) 1.22; 95% confidence interval (CI) 1.00–1.48] and to 0 MET-min/week (physically inactive; PM10 aHR 1.38; 95% CI 1.07–1.78) had an increased risk of CVD (P for trend <0.01). Among participants exposed to high levels of PM2.5 or PM10, the risk of CVD was elevated with an increase in PA above 1000 MET-min/week. Reducing PA may lead to subsequent elevation of CVD risk in young adults exposed to low-to-moderate levels of PM2.5 or PM10, whereas a large increase in PA in a high-pollution environment may adversely affect cardiovascular health. Combined effects of air pollution and changes in physical activity with cardiovascular disease in young adults.

Importance Previous studies have shown a U- or J-shaped association of body mass index (BMI) or change in BMI with coronary heart disease (CHD) among middle-aged and elderly adults. However, whether a similar association exists among young adults is unclear. Objective To determine whether an association exists between BMI or BMI change with CHD among young adults. Design, Setting, and Participants This population-based longitudinal study used data obtained by the Korean National Health Insurance Service from 2002 to 2015. The study population comprised 2 611 450 men and women aged between 20 and 39 years who underwent 2 health examinations, the first between 2002 and 2003 and the second between 2004 and 2005. Exposures World Health Organization Western Pacific Region guideline BMI categories of underweight, normal weight, overweight, obese grade 1, and obese grade 2 derived during the first health examination and change in BMI calculated during the second health examination. Main Outcomes and Measures Body mass index (calculated as weight in kilograms divided by height in meters squared). Absolute risks (ARs), adjusted hazard ratios (aHRs), and 95% CIs for acute myocardial infarction or CHD during follow-up from 2006 to 2015. Results Data from 1 802 408 men with a mean (SD) age of 35.1 (4.8) years and 809 042 women with a mean (SD) age of 32.5 (6.3) years were included. The mean (SD) BMI was 23.2 (3.2) for the total population, 24.0 (3.0) for men, and 21.4 (2.9) for women. Compared with normal weight men, overweight (AR, 1.38%; aHR, 1.18 [95% CI, 1.14-1.22]), obese grade 1 (AR, 1.86%; aHR, 1.45 [95% CI, 1.41-1.50]), and obese grade 2 (AR, 2.69%; aHR, 1.97 [95% CI, 1.86-2.08]) men had an increased risk of CHD (P < .001 for trend). Similarly, compared with normal weight women, overweight (AR, 0.77%; aHR, 1.34 [95% CI, 1.24-1.46]), obese grade 1 (AR, 0.95%; aHR, 1.52 [95% CI, 1.39-1.66]), and obese grade 2 (AR, 1.01%; aHR, 1.64 [95% CI, 1.34-2.01]) women had an increased risk of CHD (P < .001 for trend). Compared with participants who maintained their weight at normal levels, those who became obese had elevated CHD risk among men (0.35% increase in AR; aHR, 1.35 [95% CI, 1.17-1.55]) and women (0.13% increase in AR; aHR, 1.31 [95% CI, 0.95-1.82]). Weight loss to normal levels among obese participants was associated with reduced CHD risk for men (0.58% decrease in AR; aHR, 0.77 [95% CI, 0.64-0.94]) and women (0.57% decrease in AR; aHR, 0.66 [95% CI, 0.45-0.98]). Conclusions and Relevance Obesity and weight gain were associated with elevated risk of CHD among young adults in this study. Studies that prospectively determine the association between weight change and CHD risk are needed to validate these findings.

In a cohort of 190,599 participants from The National Health Insurance Service-National Health Screening (NHIS-HEALS) study, we investigated the association of changes in the predicted body composition and metabolic profiles with the risk of metabolic syndrome (MetS) in the general population, which was hitherto incompletely elucidated. At baseline and follow-up examinations, the body composition, including lean body mass (LBM), body fat mass (BFM), and appendicular skeletal mass (ASM), were estimated using a prediction equation, and the risk of MetS was analyzed according to relative body composition changes. An increase in relative LBM and ASM decreased the risk of MetS in men and women (adjusted odds ratio (aOR), 0.78 and 0.80; 95% confidence interval (CI), 0.77–0.79 and 0.79–0.81, respectively; all p < 0.001). As relative LBM and ASM increased, the risk of MetS was more significantly reduced in the group with higher baseline BMI and body fat mass index (BFMI)(all p-trend < 0.001). In men, when the relative LBM increased (aOR, 0.68; 95% CI, 0.63–0.73), the risk of MetS was low despite increased BMI. Thus, our findings suggested that an increase in the relative LBM and ASM reduced the risk of MetS, whereas an increase in the relative BFMI increased the risk of MetS; this result was consistent in men despite an increase in BMI.