Appropriate scaling approach for evaluating peak VO2 development in Southern Chinese 8 to 16 years old.

OBJECTIVE: To investigate scaling approaches for evaluating the development of peak VO2 and improving the identification of low cardiopulmonary fitness in Southern Chinese children and adolescents. METHODS: Nine hundred and twenty Chinese children and adolescents (8 to 16 years) underwent graded cardiopulmonary exercise test on a treadmill until volitional exhaustion. Peak VO2 was corrected for the effects of body mass by ratio or allometric scaling. Z score equations for predicting peak VO2 were developed. Correlations between scaled peak VO2, z scores, body size and age were tested to examine the effectiveness of the approach. RESULTS: Eight hundred and fifty-two participants (48% male) were included in the analyses. Absolute peak VO2 significantly increased with age in both sexes (both P<0.05), while ratio-scaled peak VO2 increased only in males (P<0.05). Allometrically scaled peak VO2 increased from 11 years in both sexes, plateauing by 12 years in girls and continuing to rise until 15 years in boys. Allometically scaled peak VO2 was not correlated with body mass, but remained correlated with height and age in all but the older girls. Peak VO2 z score was not correlated with body mass, height or age. CONCLUSIONS: Absolute and allometric scaled peak VO2 values are provided for Hong Kong Chinese children and adolescents by age and sex. Peak VO2 z scores improve the evaluation of cardiopulmonary fitness, allowing comparisons across ages and sex and will likely provide a better metric for tracking change over time in children and adolescents, regardless of body size and age.

Follow up of aerobic capacity in children affected by severe acute respiratory syndrome.

BACKGROUND AND OBJECTIVE: The aim of this study was to investigate the aerobic capacity of children 3 years after they were diagnosed with severe acute respiratory syndrome (SARS). METHODS: Twenty-seven patients who completed both pulmonary function and maximal aerobic capacity tests at 6 and 15 months after the acute illness were invited to return for reassessment. RESULTS: Twenty-one patients (median age 18.2 years, interquartile range (IQR) 16.5-19.7) completed all investigations at 36 months. Pulmonary function was normal in all patients. Maximal aerobic capacity, peak oxygen pulse (peak VO(2) ) and ventilatory anaerobic threshold showed significant improvements compared with values measured at 6 months in both boys and girls. In girls, ventilatory efficiency (ventilatory equivalents for oxygen and carbon dioxide) and perfusion of the lungs (end-tidal partial carbon dioxide pressure) had not increased further compared with the values measured at 15 months. Although peak VO(2) improved further at 36 months in patients with or without persistent radiological abnormalities, the values were 68% (IQR 50-84) and 74% (IQR 60-99), respectively, of those for normal control subjects. CONCLUSIONS: There were improvements in aerobic capacity at 36 months in children affected by SARS; however, the measured values remained suboptimal.

Night sweats in children: prevalence and associated factors.

OBJECTIVE: The authors aimed to examine the prevalence and factors associated with night sweats (NS) in primary school children. STUDY DESIGN: Cross-sectional design. RESULTS: Among 6381 children (median age 9.2 (7.7-10.7) years) with complete information on NS, 3225 were boys (50.5%). 747 children (11.7%) were reported to have weekly NS in the past 12 months. Boys were more likely than girls to have NS (p<0.0001). Children with NS were more likely to have sleep-related symptoms and respiratory and atopic diseases. In addition, they were more likely to be hyperactive and have frequent temper outbursts. Using an ordinal regression model, NS was found to be significantly associated with male gender, younger age, allergic rhinitis, tonsillitis and symptoms suggestive of obstructive sleep apnoea, insomnia and parasomnia. CONCLUSION: NS is prevalent among school-aged children and is associated with the presence of sleep-related symptoms and respiratory and atopic diseases.

Socioenvironmental factors associated with constipation in Hong Kong children and Rome III criteria.

OBJECTIVE: Data regarding the prevalence of constipation in the general population of Asian children using internationally standardized definitions are scarce. Environmental factors surrounding a child's day to day living may trigger or perpetuate constipation and encourage postponement of defecation. METHODS: A territory-wide cross-sectional questionnaire survey was conducted in 2318 Hong Kong Chinese elementary school students. Constipation was defined by pediatric Rome III criteria. RESULTS: The mean age of the children was 9 ± 1.9 years; 51% were boys. Two hundred eighty-two children (12.2%, 95% confidence interval [CI] 10.9%-13.5%) were found to have constipation. Children ages 6 to 7 years had the highest prevalence (16.8%, 95% CI 13.8%-19.8%). There was no difference in prevalence between boys and girls (11.6% vs 12.3%; P > 0.05) and between obese and nonobese children (11.5% vs 11.1%; P > 0.05). In univariate analysis, constipation was found to be significantly more prevalent among those children who lived with neither parent, had inadequate company of parents at home, refused to pass bowel movements in school, spent long hours doing homework, had inadequate sleep, and had decreased fiber intake and frequent consumption of fast food (P < 0.05). Multivariate analysis identified refusal to pass bowel movements in school toilets (odds ratio [OR] 1.97, 95% CI 1.42%-2.74%), having dinner with one/both parents <50% of time (OR 1.52, 95% CI 1.01%-2.31%), nighttime sleep <7 hours (OR 1.87, 95% CI 1.04%-3.33%), and frequent consumption of fast food (OR 1.14, 95% CI 1.03%-1.26%) to be independent factors associated with constipation. CONCLUSIONS: Socioenvironmental factors are associated with childhood constipation, and bringing them to the awareness of the public may help prevent or stop the progression of childhood constipation at its early stages.

Nocturnal enuresis in children: prevalence, correlates, and relationship with obstructive sleep apnea.

OBJECTIVES: To examine the prevalence and correlates of nocturnal enuresis (NE) in primary school children, and to compare the prevalence of NE in children with and those without obstructive sleep apnea (OSA). STUDY DESIGN: Parents of children aged 6-11 years completed a questionnaire eliciting information on sleep-related symptoms, demography, and family and past medical history. Children screened due to high risk for OSA, along with a randomly chosen low-risk group, underwent overnight polysomnography (PSG). RESULTS: A total of 6147 children (3032 girls) were studied. The overall prevalence of NE (≥1 wet night/month) was 4.6% (6.7% of boys and 2.5% of girls). Boys had a significantly greater prevalence across all age groups. In 597 children (215 girls) who underwent PSG, the prevalence of NE was not greater in children with OSA, but was increased with increasing severity of OSA in girls only. Boys with NE had longer deep sleep duration. Sex and sleep-related symptoms were associated with NE. CONCLUSIONS: This community-based study demonstrated a sex-associated prevalence of NE in relation to increasing OSA severity.

Epidemiology of obstructive sleep apnoea syndrome in Chinese children: a two-phase community study.

OBJECTIVE: To determine the prevalence and risk factors of obstructive sleep apnoea syndrome (OSAS) in Chinese children using a two-phase community-based study design. METHODS: Children from 13 primary schools were randomly recruited. A validated OSAS screening questionnaire was completed by their parents. Children at high risk of OSAS and a randomly chosen low-risk group were invited to undergo overnight polysomnographic study and clinical examination. The the sex-specific prevalence rate was measured using different cutoffs (obstructive apnoea hypopnoea index ≥ 1, ≥ 1.5, ≥ 3 and ≥ 5 and obstructive apnoea index ≥ 5) and risk factors associated with OSAS were evaluated with logistic regression. RESULTS: 6447 completed questionnaires were returned (out of 9172 questionnaires; 70.3%). 586 children (9.1%; 405 boys and 181 girls) children belonged to the high-risk group. A total of 619 (410 and 209 from the high and low-risk group, respectively) subjects underwent overnight polysomnagraphy. Depending on the cutoffs, the prevalence rate of childhood OSAS varied from 4.8% to 40.3%. Using the International Criteria of Sleep Disorders version II, the OSAS prevalence for boys and girls was 5.8% and 3.8%, respectively. Male gender, body mass index z-score and increased adenoid and tonsil size were independently associated with OSAS. CONCLUSIONS: The prevalence rate of OSAS in children was contingent on the cutoff used. The inclusion of symptoms as a part of the diagnostic criteria greatly reduced the prevalence. A further prospective and outcome study is needed to define a clinically significant diagnostic cutoff for childhood OSAS.

Prevalence and risk factors of habitual snoring in primary school children.

OBJECTIVE: Our study aimed to determine the prevalence of habitual snoring (HS) in primary school children and to evaluate the diurnal symptoms and conditions that may be associated with it. METHODS: A validated questionnaire completed by parents was used to assess the sleep and daytime behaviors of Chinese children aged 5 to 14 years. Thirteen primary schools in two representative districts were randomly selected. RESULTS: A total of 6,349 out of 9,172 questionnaires (response rate 69.2%) with complete answers were returned. The prevalence rate of HS was 7.2%. Male sex (odds ratio [OR] [95% CI]: 2.5 [1.7-3.6]), BMI z score (OR [95% CI]: 1.4 [1.1-1.6]), maternal HS (OR [95% CI]: 3.4 [2.0-5.7]), paternal HS (OR [95% CI]: 3.8 [2.7-5.5]), allergic rhinitis (OR [95% CI]: 2.9 [2.0-4.2]), asthma (OR [95% CI]: 2.4 [1.2-5.2]), nasosinusitis (OR [95% CI]: 4.0 [1.5-10.6]), and tonsillitis (OR [95% CI]: 3.1 [1.9-5.1]) in the past 12 months were identified to be independent risk factors associated with HS. HS was also associated with daytime, nocturnal, parasomniac, and sleep-related breathing symptoms. HS was demonstrated to be an independent risk factor for parent-reported poor temper (OR [95% CI]: 1.9 [1.4-2.5]), hyperactivity (OR [95%CI]: 1.7 [1.2-2.5]), and poor school performance (OR [95% CI]: 1.7 [1.2-2.5]). CONCLUSIONS: HS was a significant and prevalent problem in primary school children. Male sex, obesity, parental HS, atopic symptoms, and history of upper respiratory infections were significant risk factors. HS was also associated with sleep-disordered breathing symptoms and adverse neurobehavioral outcomes.

Adipokines in children with obstructive sleep apnea and the effects of treatment.

BACKGROUND: The objective of this study was to evaluate circulating adipokines concentration in children with and without obstructive sleep apnea (OSA) and to determine the effects of treatment of OSA on their plasma concentration. METHODS: Children with habitual snoring and symptoms suggestive of OSA were consecutively recruited. Their parents completed a sleep apnea symptom questionnaire, and the subjects underwent physical examination and an overnight polysomnography (PSG). OSA was diagnosed if they had an obstructive apnea index > 1. Fasting serum adiponectin, leptin, and lipid profiles were taken after overnight PSG. The subjects were divided into groups as obese, nonobese, and with and without OSA for comparison. RESULTS: One hundred forty-one children, of whom 96 were boys, with a median (interquartile range) age of 10.8 (8.5-12.8) years were recruited. Forty-three subjects had OSA. Subjects with OSA did not have significantly different adiponectin and leptin concentrations than those without OSA for both the obese and nonobese groups. Stepwise multiple linear regressions revealed that systolic BP, age, high-density lipoprotein cholesterol, and BMI z-score were independently associated with adiponectin, whereas diastolic BP, triglyceride, height, and BMI z-score were independently associated with leptin concentration. Sixteen children with OSA underwent treatment, and there was reduction in their plasma adiponectin concentration after intervention, but such change became insignificant after controlling for change in the BMI z-score. CONCLUSIONS: BMI rather than OSA was the main determinant of adipokines in children.

Measurement of pubertal status with a Chinese self-report Pubertal Development Scale.

This cross sectional study of 290 Chinese children aged 8-18 years, evaluated a Chinese version of the self-reported Pubertal Development Scale (PDS) against both raters' and self-reported Tanner assessment of pubertal status. Children completed both the self-reported PDS and self-reported Tanner pubertal questionnaire prior to physical examination through visual depiction by a same gender rater. Puberty Category Scores (PCS) which were derived from the PDS, was used to categorize children into one of five pubertal development stages. Tanner derived composite stage (TDCS) which was derived from the Tanner pubertal questionnaires, was used to compare with PCS to obtain the inter-rater agreement. Moderately high agreements were found between raters' TDCS and PCS in girls [weighted kappa (WK) 0.57 (0.44, 0.71); Kendalltau-b 0.60 (0.51, 0.69)] and in boys [WK 0.58 (0.47, 0.69), Kendalltau-b 0.50 (0.38, 0.62)]. The correlation between self-reported PDS and rater's assessment was substantial in girls [Kendalltau-b 0.61 (0.54, 0.69)] and moderate in boys [Kendalltau-b 0.49 (0.38, 0.61)]. The Hong Kong Chinese children and adolescents were able to reliably estimate their own sexual maturation status (SMS) using a Chinese version PDS. This instrument may be useful in epidemiological studies when cost, privacy and other concerns preclude the use of other SMS assessment tools.

Leukotriene receptor antagonist in the treatment of childhood allergic rhinitis--a randomized placebo-controlled study.

OBJECTIVE: This study was designed to assess the hypothesis that leukotriene receptor antagonists (LTRAs) would provide additional symptom relief in asthmatic children with persistent AR already taking regular antihistamine. The effects of 16-week treatment of LTRA in addition to fexofenadine (FEX) on persistent AR in asthmatic children were examined. STUDY DESIGN: Consecutive children with stable asthma and persistent AR were invited in this randomized, double-blind, placebo-controlled study. After a 2-week run-in period in which subjects were given FEX alone, they were randomly assigned to take LTRA or placebo in addition to FEX for 16 weeks, followed by 8 weeks of follow-up phase with FEX taken alone. Symptom scoring, rhinoscopy, acoustic rhinometry, spirometry, nasal secretion extraction and blood taking for IL-4 and IL-13 analysis were performed after a 2-week run-in and at the end of treatment. RESULTS: Forty-four subjects with a median (IQR) age of 12.2 (10.1-14.1) years were recruited. At week 4 of treatment, the between-group differences in the mean changes of daytime sneezing score (mean difference (95% CI) = -0.35 (-0.59, -0.12), P = 0.004), nighttime sneezing score (mean difference (95% CI) = -0.37 (-0.62, -0.11), P = 0.007) and daytime composite score (mean difference (95% CI) = -1.08 (-1.92, -0.25), P = 0.013) were significant. Acoustic rhinometry also demonstrated a nearly significant difference in nasal volume change between groups at 16 weeks of treatment (mean difference (95% CI) = 0.572 (0.090-1.054), P = 0.021). IL-4 and IL-13 were not detected in the majority of nasal secretion or serum samples. CONCLUSIONS: Additional LTRA provided a more rapid relief on sneezing at the 4-week time point. This combination therapy also maintained a greater nasal volume and this might translate to lesser nasal congestion.

Interrupter respiratory resistance in healthy Chinese preschool children.

BACKGROUND: Interrupter respiratory resistance (Rint) is useful in evaluating lung function in children who cannot perform the traditional lung function tests. However, available reference Rint values are confined to whites. Our aims were as follows: (1) to establish reference values in local preschool Chinese children, (2) to examine their relationship with demographic and anthropometric factors, and (3) to determine the 10-min and 6-week repeatability of Rint. METHODS: Rint was measured in preschool children from randomly chosen local kindergartens, and the repeatability of Rint measurement was assessed in a subgroup of subjects 10 min and 6 weeks after the initial measurement. RESULTS: Rint measurement was performed in 509 children between 4 and 6 years of age. Age, height, and weight significantly inversely correlated with Rint values. However, on multiple linear regression, height was the only variable that independently correlated with Rint. Repeat measurements obtained 10 min and 6 weeks after the initial reading in 45 children showed good agreement with little variability, and the interclass correlation coefficients for 10-min and 6-week measurements were 0.877 and 0.923, respectively. CONCLUSION: Rint reference centile curves for Chinese preschool children have been determined. Rint in preschool Chinese children has good short- and long-term repeatability.

Inflammatory cytokines and childhood obstructive sleep apnoea.

OBJECTIVE: To evaluate serum cytokine concentrations in children with and without obstructive sleep apnoea (OSA) and to investigate the effects of OSA treatment on cytokines. MATERIALS AND METHODS: Consecutive children with habitual snoring and symptoms suggestive of OSA were recruited. They completed a sleep apnoea symptom questionnaire, underwent physical examination and overnight polysomnography (PSG). OSA was diagnosed if obstructive apnoea index (OAI) >1. A blood sample was collected for analysis of IL-6, IL-8, and TNF-alpha after PSG. RESULTS: One hundred forty-two children (97 males) with a median (IQR) age of 11.1 years (9.0-12.8) were recruited. The commonest presenting symptoms were nocturnal mouth breathing, prone sleeping position and poor attention at school. Forty-seven children were found to have OSA and they had higher serum IL-6 [0.1 (0.1-0.4) vs 0.1 (0.1-0.1) pg/mL, P = 0.001] and IL-8 [1.7 (1.0-2.3) vs 1.3 (0.9-1.7) pg/mL, P = 0.029] concentrations compared to their non-OSA counterparts. Multiple regression analysis indicated that OAI was significantly associated with both IL-6 (r = 0.351, P <0.001) and IL-8 (r = 0.266, P = 0.002). Sixteen children underwent treatment and there was significant reduction in mean (SD) serum IL-8 after intervention [pre vs post levels of 1.9 (1.0) vs 1.1 (0.6) pg/mL, P = 0.001] independent of weight loss. CONCLUSION: Children with OSA had elevated levels of pro-inflammatory cytokines that normalised following treatment suggesting that the inflammatory response is potentially reversible. Early detection and intervention may be beneficial.

Reliability of pubertal self-assessment in Hong Kong Chinese children.

AIM: To validate a Tanner stages self-assessment questionnaire using gender-specific line drawings and brief explanatory text in Chinese. DESIGN: A cross sectional study design. SETTING: One primary and two secondary schools. PARTICIPANTS: 172 boys and 182 girls aged between 8 and 18 years. MAIN OUTCOME MEASURES: Students' self-assessments of pubertal maturation were compared with assessments made by a same gender rater using visual depiction physical examination. Raters' physical examinations were performed after the children had answered the self-assessment questionnaire individually and in private. Raters were blinded to the self-assessment results. Accuracy rates and weighted kappa statistic were used to evaluate the degree of agreement between children and raters. RESULTS: Substantial to almost perfect agreement was found between self- and rater's assessments of breast development and pubic hair growth in girls [weighted kappa 0.72 (P < 0.0001, 95% CI 0.66, 0.79) and 0.83 (P < 0.0001, 95% CI 0.78, 0.87) respectively]. Moderate to substantial agreement was found between self- and rater's assessments of male genital development and pubic hair growth [weighted kappa 0.58 (P < 0.0001, 95% CI 0.48, 0.68) and 0.80 (P < 0.0001, 95% CI 0.74, 0.86) respectively]. Most agreements between self- and rater's assessments differed by only one Tanner stage. Agreement was higher for girls than boys. Girls tended to overestimate their breast stages and boys tended to underestimate their genitalia development. CONCLUSION: This study confirms that a Tanner pubertal self-assessment questionnaire with line drawings and explanatory Chinese text can reliably estimate sexual maturation status in Hong Kong Chinese children.

C-reactive protein in children with obstructive sleep apnea and the effects of treatment.

OBJECTIVE: To evaluate C-reactive protein (CRP) concentration in children with OSA and to determine the effects of treatment for OSA on its serum concentration. METHODS: Consecutive children with habitual snoring and symptoms suggestive of OSA were recruited. They completed a sleep apnea symptom questionnaire, underwent physical examination and an overnight polysomnography (PSG). Fasting serum CRP and lipid profile were taken after overnight PSG. OSA was diagnosed if obstructive apnea index (OAI)>1. RESULTS: One hundred forty-one children with a median (IQR) age of 10.8 (8.5-12.8) years were recruited. There were 96 boys and the commonest presenting symptoms were nocturnal mouth breathing, prone sleeping position and poor attention at school. Forty-five children were found to have OSA and those with moderate disease (OAI>5) had significantly higher CRP levels compared to their non-OSA counterparts [1.3 (0.8-3.6) vs. 0.7 (0.2-2.0), P=0.01]. Stepwise linear multiple regression analysis indicated that OAI was independently associated with CRP (beta coefficient=0.013, P=0.001). Sixteen children underwent treatment and there was significant reduction in their serum CRP after intervention [pre vs. post-CRP, 1.3 (0.6-4.1) vs. 0.4 (0.2-1.3), P=0.033]. A significant correlation was also demonstrated between change in CRP and change in OAI (r=0.593, P=0.042) following treatment for OSA. CONCLUSION: Children with OSA may have associated systemic inflammation as reflected by a raised CRP that decreased significantly following treatment.

Standard reference for the six-minute-walk test in healthy children aged 7 to 16 years.

RATIONALE: We have previously reported that the six-minute-walk test (6MWT) is a reliable and valid functional test for assessing exercise tolerance and endurance. There is a lack of pediatric standard reference for the 6MWT. OBJECTIVES: To construct height-specific standards for the 6MWT for children aged 7 to 16 years. METHODS: The anthropometric data, spirometric lung function, and six-minute-walk distance (6MWD) of Chinese children aged 7 to 16 years were prospectively measured using standardized protocols. The findings were used to construct height-specific standards for the 6MWT. The least mean square (LMS) method using maximum penalized likelihood was used to facilitate model fitting. Factors significantly associated with 6MWD were also determined. MEASUREMENTS AND MAIN RESULTS: From January 2005 to April 2006, a total of 1,445 subjects were studied. The measured variables showed a normal distribution. Height-specific reference standards for 6MWT were constructed for both male and female children. Forward stepwise multiple regression analysis revealed height and difference in heart rate before and after the walk test to be important clinical variables associated with 6MWD. CONCLUSIONS: These 6MWD standards will provide useful references for the care of pediatric patients.

Fetal methylmercury exposure as measured by cord blood mercury concentrations in a mother-infant cohort in Hong Kong.

This study was designed to examine newborn infants in Hong Kong prenatally exposed to levels of methylmercury considered to increase risk of neurotoxic effects and to examine subject characteristics that modify the degree of prenatal mercury exposure. Mercury concentrations in 1057 sets of maternal and cord blood samples and 96 randomly selected maternal hair samples were measured. Subject characteristics were measured or collected by questionnaire. Of the 1057 cord blood samples collected only 21.6% had mercury concentrations less than 29 nmol/L (5.8 micro g/L). Median maternal hair mercury concentration was 1.7 ppm. The geometric mean cord to maternal blood mercury ratio was 1.79 to 1. Increasing maternal fish consumption and maternal age were found to be associated with increased cord blood mercury concentrations. Marine fish consumption increased cord blood mercury concentrations more than freshwater fish (5.09%/kg vs 2.86%/kg). Female babies, maternal alcohol consumption and increasing maternal height were associated with decreased cord blood mercury concentrations. Pregnant women in Hong Kong consume large amounts of fish and as a result, most of their offspring have been prenatally exposed to moderately high levels of mercury. In this population, pregnant women should choose freshwater over marine fish and limit fish consumption.

Sputum induction in children with asthma: a tertiary-center experience.

Our aims were 1) to report on our experience with sputum induction (SI), and 2) to determine predictive factors associated with successful SI in asthmatic children. Children with asthma attending the chest clinic of a university teaching hospital between October 2003-December 2004 were recruited. They completed a visual analogue scale for symptom severity, and underwent physical examination, skin-prick test, exhaled nitric oxide (eNO) measurement, spirometry, and SI. Adequate sputum contained <50% squamous epithelial cells. Predictors for successful induction were evaluated using multivariate logistic regression analysis. One hundred and thirty subjects were recruited. The median age was 11.25 years (range 7.0-17.5), and the majority were boys (75%). All except two had normal percent predicted forced expired volume in 1 sec (>80%). The median eNO was 48.95 ppb. Sputum induction was successful in 93 subjects (74.5%). Sore throat and chest discomfort occurred in 20 (15%) and 8 (6%) subjects, respectively, and the procedure was prematurely terminated in three cases. Levels of eNO were found to be a predictor for successful induction (area under the ROC (receiver operator characteristics curves) curve, 0.634). Sputum induction was well-tolerated by all subjects, and was successful in 74.5% of cases. Exhaled nitric oxide may be a useful marker for successful induction.