Recovery heart rate (RHR) has been used in adults to evaluate cardiovascular (CV) fitness, but less is known about RHR in children. Data from 1,276 participants in Project Healthy Schools, a school-based intervention in southeast Michigan, were collected. In addition, to demographic characteristics, physiologic factors examined included body mass index (BMI), lipid and glucose levels, blood pressure, and HR. Information on diet, physical activity, and sedentary behavior was collected through self-report. RHR was determined by measurement of HR after a 3-minute step test. Using quartiles of RHR as a marker of fitness, associations with demographic, physiologic, and behavioral factors were explored using χ(2) and Student t tests. Compared with children in the lowest quartile of RHR (i.e., most fit), those in the upper quartile of RHR (i.e., least fit) had greater mean LDL cholesterol (93.0 vs. 86.7 mg/dL; P = 0.02) and lower mean HDL cholesterol (50.9 vs. 55.9 mg/dL; P < 0.001). Children in the upper 95 % of BMI had greater mean RHR compared with those in the normal BMI range (116.6 vs. 100.3 kg/m(2)). Children in the upper quartile of RHR reported fewer days of vigorous to moderate exercise per week compared with children in the lowest quartile of RHR [4.8 vs. 4.1 (P < 0.001) for moderate exercise and 3.6 vs. 3.0 (P = 0.001) for vigorous exercise]. Among middle school children, RHR appears to be associated with physiologic parameters and health behaviors. RHR may be useful for identifying children at increased risk for developing CV risk factors.
Sodium channels play a crucial role in initiation, propagation, and maintenance of cardiac excitation throughout the heart. Indeed, dysfunctional sodium channels have been shown to be responsible for several inherited cardiac electrical disorders, such as Long QT and Brugada syndromes (BrS), potentially leading to fatal arrhythmic events. Genetic approaches and functional experiments using heterologous systems have enabled the characterization of the molecular determinants involved in these disorders and their consequences on ion channel function. The improved understanding of the mechanisms leading to these cardiac arrhythmic events represents a first step in the development of therapeutic treatments.
To examine factors associated with low high-density lipoprotein cholesterol (HDL-C) levels among middle school children. HDL-C levels were the primary outcome of interest. A total of 1,104 middle-school children (mean age 11.6 years, 51.2% female) were included in this analysis, of whom 177 (16%) had an HDL-C level ≤40 mg/dL. More than half of those with low HDL-C were overweight or obese (62.2%) and had greater systolic and diastolic blood pressure, triglyceride (TRG) levels, and low-density lipoprotein cholesterol levels compared with children with an HDL-C level >40 mg/dL. Among those with an HDL-C ≤ 40 mg/dL, 35% also had body mass index ≥85% and TRG levels ≥150 mg/dL. Exercise habits were significantly associated with HDL-C level, whereas sedentary behaviors, such as screen time, were not significantly associated with HDL-C level. Fruit and vegetable intake was also not significantly associated with HDL-C level. Children with low HDL-C levels are more likely to be overweight and to have other physiological indicators of increased cardiovascular risk. Further research is needed to determine if school-based interventions can result in long-term improvements in HDL-C.
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