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 Association's 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.

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.

Ambulatory blood pressure before and after adenotonsillectomy in children with obstructive sleep apnea.

INTRODUCTION: Hypertension is found to be associated with obstructive sleep apnea (OSA) in both children and adults. But data on the effect of blood pressure after adenotonsillectomy (AT) for children with OSA are limited and controversial. OBJECTIVE: To assess the impact of AT on different parameters of 24-h ambulatory blood pressure monitoring in children with OSA. METHODS: We retrospectively reviewed records of OSA children who had undergone AT and a repeated sleep polysomnography after AT from 2001 to 2008. RESULTS: Forty-four children were identified and included in the analysis. The mean apnea-hypopnea index (AHI) dropped from 14.14+/-15.9 to 3.3+/-7.1. (p<0.001). Twenty (45%) were cured of OSA. After AT, the diastolic BP load decreased significantly. Six out of eight (75%) hypertensive children became normotensive after surgery. For the pre-AT hypertensive group, both systolic and diastolic blood pressure decreased significantly during sleep after AT. However, eight children who were normotensive before AT became hypertensive after AT. These 10 post-AT hypertensive patients were more likely to have post-AT AHI>1 than the post-AT normotensive group, although the difference did not reach statistical significance. CONCLUSION: In the current cohort of OSA children, 44% were cured of OSA and a significant decrease in overall diastolic blood pressure load in 24-h ambulatory blood pressure was achieved after adenotonsillectomy for children with OSA. But hypertension may persist or even occur in those previously normotensive children despite the improvement in AHI. Persistence of OSA may be a risk factor and further study is required. Cure of OSA should not be assumed after AT and follow-up PSG should be performed together with 24-h ambulatory blood pressure monitoring. In light of the current findings, long term study of the blood pressure is warranted for children with OSA.

Twenty-four-hour ambulatory BP in snoring children with obstructive sleep apnea syndrome.

INTRODUCTION: Obstructive sleep apnea syndrome (OSAS) is a known risk factor for hypertension in adults. This relationship is less clear in childhood OSAS. OBJECTIVE: This study examined the relationship between OSAS and 24-h ambulatory BP (ABP), a more accurate assessment than casual BP, in children with snoring. METHODS: Snoring children aged 6 to 15 years who underwent polysomnography in the sleep laboratory were recruited. MEASUREMENT: Twenty-four-hour ABP monitoring was initiated a few hours before polysomnography. The children were classified into two groups: a high apnea-hypopnea index (AHI) group (obstructive AHI > 5/h), and a low-AHI group (AHI < or = 5/h). Mean sleep, wake, and 24-h systolic BP (SBP) and diastolic BP (DBP) were recorded. A child was considered a "nondipper" if his or her mean SBP and DBP did not decrease by >/= 10% during sleep. RESULTS: Ninety-six children (mean age +/- SD, 9.4 +/- 2.8 years) were recruited. Forty-one children were obese. When awake, the high-AHI group children had a significantly higher SBP. When asleep, both SBP and DBP were higher in the high-AHI group. Age, body mass index (BMI) z score, and desaturation index (DI) were significant predictors for elevated sleep DBP. BMI z score was the only significant predictor for wake and sleep SBP. Sixteen children (17%) had hypertension, and all were nondippers. Obese children in the high-AHI group had a significantly higher prevalence of hypertension than obese children in the low-AHI group. This relationship was not found in nonobese children. CONCLUSION: The current study shows that increased DI contributed to the elevation of sleep DBP elevation.