Hung-Kwan So

Prevalence and risk factors for hypertension in Hong Kong Chinese adolescents: waist circumference predicts hypertension, exercise decreases risk

Purpose To determine the prevalence, risk factors for and patterns of hypertension in Chinese adolescents based on a territory-wide school based screening programme in Hong Kong. Methods Cross-sectional anthropometric and oscillometric blood pressure (BP) measurements and lifestyle information were obtained as part of a growth survey of students from randomly selected secondary schools in Hong Kong. Those with blood pressure ≥95th centile were screened a second or third time. Hypertension is defined as elevated blood pressure on three separate occasions. The independent effects of age, sex, body mass index, high waist circumference (≥85th centile), sleep duration, family history of hypertension and frequency of exercise on hypertension were explored by multivariate analysis. Results Among the 6193 students screened, the prevalence of elevated blood pressure on the first, second and third screens was 9.54%, 2.77% and 1.44% respectively. Hypertension was more likely to be systolic. High waist circumference (≥85th centile) was independently associated with a higher risk of hypertension (adjusted OR 2.4), while exercising twice or more per week was protective (adjusted OR 0.28). Conclusions The prevalence of hypertension in Hong Kong Chinese adolescents is 1.44%. The current study shows high waist circumference is a predictor of hypertension in adolescents, while increased physical activity is a protective factor. Incorporating waist circumference into screening protocols may increase the sensitivity of cardiovascular risk stratification. Healthcare providers should be strong advocates helping to prevent obesity and promote physical activity in adolescents and children.

Validation of A&D TM-2430 upper-arm blood pressure monitor for ambulatory blood pressure monitoring in children and adolescents, according to the British Hypertension Society protocol.

ObjectiveThe A&D TM-2430 ambulatory blood pressure (BP) monitor has been validated in adults but not in a young population. We sought to validate the device monitoring in children and adolescents, according to the British Hypertension Society (BHS) protocol. MethodsThe A&D TM-2430 is an automated oscillometric upper-arm device for ambulatory BP monitoring. Nine consecutive measurements were taken in 61 children (mean age, 9.8 years; range, 5–15 years) according to the BHS criteria. Overseen by an independent supervisor, measurements were recorded by two observers blinded from each other’s readings and from the device readings. ResultsThe mean difference±SD between the observers and device measurements was 0.73±1.64 mmHg for systolic blood pressure (SBP) and −1.23±1.65 mmHg for diastolic blood pressure (DBP), respectively, with an interobserver difference of 4 mmHg. The cumulative percentages of differences within 5, 10, and 15 mmHg were 89, 95, and 98% for SBP and 67, 88, and 98% for DBP. The device achieved a grade A rating for SBP and a B grade for DBP. ConclusionThe A&D TM-2430 upper-arm BP monitor has fulfilled the required BHS standards and can be recommended for measuring ambulatory BP in children and adolescent populations.

Higher exercise frequency associated with lower blood pressure in Hong Kong adolescents: a population-based study

The aim of this study was to determine the association between blood pressure and the frequency of structured physical training activity in Chinese adolescents. A total of 9558 students aged 11–18 years underwent anthropometric and blood pressure measurements in a cross-sectional growth study. Structured physical training activity was assessed by two simple self-administered questions and parents were asked to complete a questionnaire providing demographic information. Ninety per cent of eligible students participated in the study, of which 94% provided data on physical training frequency for final analysis. Of the boys, 22.6% and of the girls, 14.5% were physically active with extracurricular school exercise at least twice a week. Over half of the students did not regularly exercise except during physical education classes at school. Blood pressure had a positive correlation with body mass index (BMI). Both systolic blood pressure and diastolic blood pressure were substantially decreased with increased training frequency (P<0.05). Logistic regression adjusting for age, family history of hypertension, BMI and sleep duration showed that exercising two or more times a week had a negative relation with hypertension (odds ratio: 0.63, 95%CI 0.47–0.85). In conclusion, structured physical training activity of two or more times a week has a beneficial effect on blood pressure in Hong Kong children aged 11–18 years.

Oscillometric 24-h ambulatory blood pressure reference values in Hong Kong Chinese children and adolescents

Objectives: We aimed to establish community-based normal reference values of 24-h ambulatory blood pressure monitoring (ABPM) for Chinese children and adolescents. Furthermore, we investigated how excluding overweight children affects BP percentiles and compared them with German references. Methods: In this territory-wide cross-sectional prospective cohort study, 1445 Hong Kong Chinese children and adolescents aged 8–17 years with body height between 119 and 185 cm were recruited. Their ABPM assessment was performed using validated arm oscillometric recorders (A&D TM-2430) and complied with American Heart Associations recommendations. The reference tables were constructed using the LMS method to normalize skewed distribution of ABP data to sex and age or height. Results: The ambulatory BP was higher among boys and the difference between boys and girls progressively widened with age. An increasing trend in daytime and night-time SBP and DBP with age and height was observed in both sexes. The age-specific and sex-specific 95th percentiles from nonoverweight children (n = 1147; 79%) were lower than the whole cohort by up to 2.5 and 1 mmHg for SBP and DBP, respectively. In comparison, our overall and nonoverweight reference standards were generally higher than corresponding German references. Conclusion: The study provides ambulatory BP standards for Chinese children, with sex-related age-specific and height-specific percentiles. Further longitudinal studies are required for investigating its clinical utility in Chinese.

Resting heart rate in children and adolescents: association with blood pressure, exercise and obesity

Objective Resting heart rate (RHR) is increasingly recognised as a prognostic marker for long term cardiovascular outcomes in adults. This study assessed associations of RHR with blood pressure (BP), anthropometry and exercise in a large representative sample of Hong Kong children. Study design, setting and subjects A territory-wide growth survey carried out in 2005–2006 included students sampled from each of Hong Kongs 18 districts. RHR and BP were measured by validated oscillometric BP devices and anthropometric data and exercise frequency were recorded. Multiple linear regressions were used to test associations among RHR and BP, anthropometry and exercise frequency. Results Data on 14 842 children aged 6–18 years were available. Multiple linear regression analyses showed that RHR was positively associated with BP, and negatively associated with age and exercise frequency (p<0.001). RHR was more positively linked to waist circumference among the anthropometric measurements, and positive independent association was only identified in boys (p<0.001). Conclusions Elevated RHR is independently associated with elevated BP in children, whereas increased structured exercise is related to lower RHR.

Socioeconomic Gradient in Childhood Obesity and Hypertension: A Multilevel Population-Based Study in a Chinese Community

Background This study aims to assess evidence for any socioeconomic gradients in childhood obesity and hypertension in a population-representative sample in Hong Kong, China. Methods The data of a stratified random sampled growth survey collected in 2005–2006 was matched with a population by-census. Obesity was defined using the International Obesity Task Force standard and hypertension was defined using the Hong Kong norm table. Family socioeconomic status (SES) was measured by maternal education level. Neighbourhood SES was measured by median household income of the neighbourhood. Multilevel Poisson regression models with robust standard error were used to test the association. Body mass indices of children’s parents were included as potential confounders. Intra-school/neighbourhood correlations were adjusted using random factors. Results Totally 14842 children (age 6–19 years) included in the analysis, in which 16.6% of them were overweight or obese. Children whose mother only completed secondary school or below had higher risk of childhood obesity (RR 1.41, 95% CI 1.13–1.76, p = 0.003) and hypertension (RR 1.18, 95% CI 1.01–1.36, p = 0.03). Meanwhile, children in the lowest neighbourhood SES group had higher risk of childhood underweight (RR 1.61, 95% CI 1.04–2.49, p = 0.03), overweight (RR 1.35, 95% CI 1.05–1.72, p = 0.02), and obesity (RR 2.07, 95% CI 1.11–3.88, p = 0.02). Conclusions Socioeconomic gradient in childhood obesity and hypertension existed in Hong Kong, one of the most developed cities in China. These results have implications for policymakers and public health experts and highlight the need to monitor trends in other parts of China.

Lifestyle Intervention Using an Internet-Based Curriculum with Cell Phone Reminders for Obese Chinese Teens: A Randomized Controlled Study

Objectives Obesity is an increasing public health problem affecting young people. The causes of obesity are multi-factorial among Chinese youth including lack of physical activity and poor eating habits. The use of an internet curriculum and cell phone reminders and texting may be an innovative means of increasing follow up and compliance with obese teens. The objectives of this study were to determine the feasibility of using an adapted internet curriculum and existing nutritional program along with cell phone follow up for obese Chinese teens. Design and Methods This was a randomized controlled study involving obese teens receiving care at a paediatric obesity clinic of a tertiary care hospital in Hong Kong. Forty-eight subjects aged 12 to 18 years were randomized into three groups. The control group received usual care visits with a physician in the obesity clinic every three months. The first intervention (IT) group received usual care visits every three months plus a 12-week internet-based curriculum with cell phone calls/texts reminders. The second intervention group received usual care visits every three months plus four nutritional counselling sessions. Results The use of the internet-based curriculum was shown to be feasible as evidenced by the high recruitment rate, internet log-in rate, compliance with completing the curriculum and responses to phone reminders. No significant differences in weight were found between IT, sLMP and control groups. Conclusion An internet-based curriculum with cell phone reminders as a supplement to usual care of obesity is feasible. Further study is required to determine whether an internet plus text intervention can be both an effective and a cost-effective adjunct to changing weight in obese youth. Trial Registration Chinese Clinical Trial Registry ChiCTR-TRC-12002624

Association between waist circumference and childhood‐masked hypertension: A community‐based study

The aim of this study is to determine the association between waist circumference (WC) and childhood‐masked hypertension.

Regular exercise and a healthy dietary pattern are associated with lower resting blood pressure in non-obese adolescents: a population-based study

The study aims to assess the association of diet and frequency of extracurricular physical activity (PA) on blood pressure (BP) in non-obese adolescents. A total of 7185 non-obese adolescents aged 12–18 years were analysed to elucidate the relationship between BP and exercise/eating habit. Totally, 10.3% of the boys and 4.6% of the girls who responded to the questionnaire reported undertaking regular extracurricular physical exercise ⩾3 times/week and were classified as being physically active. An unhealthy eating habit (UEH) score was constructed by counting the number of ‘yes’ responses to 11 dietary behavioural items considered to be unhealthy. In logistic regression analysis, age, body mass index, exercise frequency and UEH were significantly associated with BP (P<0.001). The odds ratios (ORs) for high BP in physically more active adolescents vs those who were less active was 0.48 (95% confidence interval (CI) 0.30–0.77). The OR for high BP in those with UEH scores in the highest quartile vs those with UEH scores in the lowest quartile was 1.63 (95% CI 1.24–2.15). In conclusion, regular exercise and a healthy diet are positively associated with lower BP even in non-obese adolescents.

Effects of resistance training on cardiovascular health in non-obese active adolescents

AIM To determine the benefits of a 10-wk resistance training programme on cardiovascular health in non-obese and active adolescents. METHODS This is a pragmatic randomised controlled intervention. The study was carried out in a Hong Kong Government secondary school. Thirty-eight lean and active boys and girls were randomised to either the resistance training group or the control group. Students in the resistance training group received in-school 10-wk supervised resistance training twice per week, with each session lasting 70 min. Main outcome measures taken before and after training included brachial endothelial dependent flow-mediated dilation, body composition, fasting serum lipids, fasting glucose and insulin, high sensitive C-reactive protein, 24-h ambulatory blood pressure and aerobic fitness. RESULTS The only training related change was in endothelial dependent flow-mediated dilation which increased from 8.5% to 9.8%. A main effect of time and an interaction (P < 0.005) indicated that this improvement was a result of the 10-wk resistance training. Main effects for time (P < 0.05) in a number of anthropometric, metabolic and vascular variables were noted; however, there were no significant interactions indicating the change was more likely an outcome of normal growth and development as opposed to a training effect. CONCLUSION Ten weeks of resistance training in school appears to have some vascular benefit in active, lean children.