Effectiveness of inactivated COVID-19 vaccine CoronaVac in children aged less than 3 years old during Omicron wave in Hong Kong.

The COVID-19 pandemic has affected people of all ages worldwide. However, there is still no information on the vaccine effectiveness (VE) of inactivated COVID-19 vaccines in children aged less than 3 years old. This study highlighted that 2 doses of CoronaVac were effective in preventing COVID-19, with a VE of 83.1 %.

Dynamics of childhood obesity in Hong Kong throughout the COVID-19 pandemic before and after the school closures: a 3-year longitudinal study.

OBJECTIVE: This study is to evaluate if there is any difference in the balance between incidence of and remission from overweight/obesity in Hong Kong school-age children before and during the COVID-19 pandemic over three years. METHODS: This is a retrospective longitudinal study that involved children aged 6-16 years from a database of the School Physical Fitness Award Scheme. RESULTS: 2765 students were longitudinally followed up for two years. The prevalence of childhood overweight/obesity was increased between the 2019 and 2021 academic years (P < 0.001). During the COVID-19 pandemic, the rate of obesity remission significantly reduced by 7.9 % (P = 0.003), at a background of a plateau of obesity among children and adolescents. CONCLUSIONS: Our study provides evidence on the impact of school closure and home confinement as a standard infection control measure for the prevention of COVID-19, which are likely to break the balance between incidence of and remission from childhood obesity.

Adolescents' attitudes to the COVID-19 vaccination.

Vaccines against COVID-19 are now available for adolescents in Hong Kong but vaccine hesitancy is a major barrier to herd immunity. This survey study explores Hong Kong adolescents' attitudes towards the COVID-19 vaccination. 2609 adolescents from across Hong Kong completed an online survey focused on the intent to vaccinate and the reasons for their choice. 39% of adolescents intended to take the COVID-19 vaccination and significant factors for this decision include: having at least one parent vaccinated, knowing somebody diagnosed with COVID-19 and receiving the influenza vaccine. Adolescents' major concerns were either the safety and efficacy of the vaccine or the risk of infection. This study has proved that even in adolescents the vaccine hesitancy model is prominent with adolescents' intentions highly related to confidence in the vaccine and perception of disease risk. Future interventions should target these specific concerns to ensure adolescents are well educated to overcome vaccine hesitancy.

Dietitian-led lifestyle modification programme for obese Chinese adolescents with non-alcoholic fatty liver disease: a randomized controlled study.

BACKGROUND: The prevalence of non-alcoholic fatty liver disease (NAFLD) in children is increasing. This study evaluated the efficacy of a dietitian-led lifestyle modification programme (D-LMP) to reduce NAFLD in obese adolescents. METHODS: Subjects with intra-hepatic triglyceride content (IHTC) equal to or greater than 5% diagnosed by proton-magnetic resonance spectroscopy (1H-MRS) were enroled and randomly assigned to either the D-LMP intervention or conventional paediatrician-led consultation (P-CON) group. Subjects in the P-CON group received usual care consisting of a consultation by a paediatrician with the child and parents every 16 weeks. Intention-to-treat analysis was used for data analysis. RESULTS: Fifty-two subjects were recruited, with 26 in each group. After the initiation phase (at week-16), there was a greater difference in the change in the IHTC and BMI z-score in the D-LMP group (P = 0.029 and <0.001, respectively) and there was a decrease in dietary intake of fat content (P = 0.019). After 52 weeks of the maintenance phase, both groups had reductions of IHTC to 2-3% and there was no intergroup difference in the rate of reduction. During the maintenance phase, parents' involvement was minimal in the D-LMP group, with only three parents accompanying their children to attend the dietitian sessions. In contrast, over 90% of the parents in the P-CON group regularly accompanied their children to attend the consultations suggesting the possibility that regular parental and paediatrician involvement may contribute to increasing awareness on fatty liver complications. Multivariate analysis showed that only reduction in body fat remained as an independent factor associated with remission of NAFLD at the end of both study phases. CONCLUSIONS: A dietitian-led lifestyle modification intervention reduced IHTC, BMI z-score and body fat in obese Chinese adolescents with NAFLD. To sustain the effect of this intervention, regular parental and paediatrician involvement may be important.

Waist-to-height ratio as a measure of abdominal obesity in southern Chinese and European children and adolescents.

BACKGROUND: Waist-to-height ratio (WHtR), with a 0.5 threshold (WHtR0.5), is regarded as a simple age- and gender-independent criterion of abdominal obesity (AO) and a better predictor than the 90th percentile of waist circumference (WCP90). OBJECTIVE: An analysis of gender and ethnic differences of WHtR and other AO indices between children and adolescents from southern China (HK: Hong-Kong, China) and Europe (LD: Lódz, Poland). SUBJECTS: Two large cross-sectional surveys of children and adolescents aged 7-19 years, one from LD (13 172) and one from HK (14 566). METHODS: The percentile and standardized values of WHtR and other parameters (WC, body mass index (BMI)) were assessed using the LMS method. The WHtR values corresponding to WCP90 and to the BMI definition of global obesity (BMIP95) were evaluated with the polynomial regression model. The compliance of the AO prevalence data, obtained with two criteria (WCP90 vs WHtR0.5) was analyzed using Cohen's kappa index (κC). RESULTS: The WHtR data of Polish subjects were generally higher than those of their HK peers, and the ethic differences increased with age. The WHtR values of HK boys showed a stronger relationship with BMI z-score. WHtR corresponding to WCP90 assumed values <0.5. An application of Cohen's kappa coefficient (κC) to Polish subjects showed either 'substantial' (κC>0.6) or 'almost perfect' (κC>0.8) agreement in the AO prevalence for both criteria (WCP90 and WHtR0.5). For these criteria, either 'fair' (κC <0.4) or 'moderate' (κC<0.6) AO consistency ratings were observed among HK girls. In HK boys, a significant difference in the prevalence of AO was observed, independent of the criterion used. CONCLUSIONS: Our results provide further evidence of the need for developing ethnic-specific WC charts and for recommending that a WHtR cutoff of 0.5 may not be appropriate to predict cardiometabolic risk in children of different ethnic groups.

Neurocognitive dysfunction and grey matter density deficit in children with obstructive sleep apnoea.

BACKGROUND: Cerebral structural changes related to obstructive sleep apnoea (OSA) have been reported in adult OSA patients; however, similar data and their associations with neurocognitive dysfunction are scarce in childhood OSA. OBJECTIVE: To compare neurocognitive function, regional grey matter density and cerebral volume in children with and without OSA. METHODS: Fifty OSA cases and 27 normal controls underwent a panel of neurocognitive tests. High resolution 3-dimensional magnetic resonance images of the brain were obtained from 23 OSA cases and 15 gender and age matched controls. Total cerebral volume and regional grey matter density were analyzed using voxel-based morphometry technique and compared between the two groups. Individuals with an obstructive apnoea hypopnoea index (OAHI) > 5 were defined as having moderate-to-severe OSA. RESULTS: Children with OSA showed significantly reduced attention and visual-fine motor coordination scores compared with controls. Grey matter volume deficit was observed in prefrontal and temporal regions of cases with moderate-to-severe OSA only. Significant negative correlations were found between the visual-fine motor coordination score and the ratio of grey matter volume over total brain volume. CONCLUSION: Children with OSA had impaired attention and visual-fine motor coordination. Regional grey matter reduction was evident in children with more severe OSA.

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 > or =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.

Implications of using World Health Organization growth reference (2007) for identifying growth problems in Hong Kong children aged 6 to 18 years.

OBJECTIVE: To evaluate the implications of replacing Hong Kong's 1993 growth references (HK1993) with the World Health Organization's 2007 references (WHO2007) for children aged 6 to 18 years. DESIGN: Cross-sectional study. SETTING: Thirty-six randomly selected primary and secondary schools in Hong Kong. PARTICIPANTS: A total of 14 842 children and adolescents aged 6 to 18 years in Hong Kong during 2005/06. MAIN OUTCOME MEASURES: Creation of age-specific z-scores for height, weight, and body mass index relative to HK1993 and WHO2007 references. RESULTS: Use of WHO2007 instead of HK1993 could classify an additional 1.4% children aged 6 to 10 years and 2.8% children aged 11 to 18 years as having a short stature. Using WHO2007, respective proportions that could be classified as underweight and obese increased by 3.5% and 2.1% among children aged 6 to 10 years, and 5.5% and 1.6% among children aged 11 to 18 years. CONCLUSIONS: Use of WHO2007 could increase clinical workload and patient and parent anxiety by 'over-diagnosing' short stature and underweight. Although WHO2007 may have a role in international comparative research, retention of HK1993 would seem appropriate from a clinical perspective.

Breakfast frequency inversely associated with BMI and body fatness in Hong Kong Chinese children aged 9-18 years.

The present study assessed the relationship between breakfast frequency and measures of obesity in Hong Kong Chinese children aged 9-18 years. A total of 11,570 children (50 % boys) underwent anthropometric measurements and completed a simple self-administered dietary behaviour questionnaire. Their parents completed a questionnaire providing demographic information. Breakfast frequency was assessed by a single question, 'How many days over the past week did you have breakfast?' Children were categorised into three groups: skippers (ate breakfast 0-2 times/week); semi-skippers (ate breakfast 3-4 times/week); non-skippers (ate breakfast 5-7 times/week), to assess all associated characteristics. Of the 3644 primary and 7926 secondary school students, 8 % (8·7 % of boys and 6·9 % of girls) and 14 % (14 % of boys and 15 % of girls), respectively, were breakfast skippers. The prevalence of obesity among breakfast skippers, semi-skippers and non-skippers was, respectively, 9·8, 10·6 and 3·8 % (P < 0·001) for primary school students and 3·9, 3·1 and 2·4 % (P < 0·001) for secondary school students. The 12 % of Hong Kong children aged 9-18 years who skipped breakfast had higher BMI, BMI z-scores and percentage of body fat (PBF) than their counterparts. The dose effects of breakfast frequency (unstandardised regression coefficient, P < 0·001) on BMI and PBF were, respectively, -0·125 kg/m2 and -0·219 % for boys and -0·165 kg/m2 and -0·353 % for girls, adjusting for physical activity per additional breakfast meal per week. Further study is recommended to elucidate whether regular breakfast consumption may have a role in the prevention of childhood obesity.

Age-based formulae to estimate children's weight in the emergency department.

OBJECTIVE: To develop an age-based weight estimation rule in a Chinese population and to compare its performance with existing formulae. DESIGN: Population-based observational study. SETTING: Schools and kindergartens in Hong Kong. SUBJECTS: Healthy Chinese children aged 1-10 years old on their last birthday. INTERVENTIONS: Weight was measured to the nearest 0.2 kg. MAIN OUTCOME MEASURES: Linear regression was used to derive a simple formula relating weight to the child's age on his or her last birthday. The accuracy and precision of different age-based weight formulae was compared using coefficient of variation, Bland Altman plots, and by determining the proportion of children with estimates >30% outside the actual weight. RESULTS: The Chinese Age Weight Rule is a simple linear formula that is more accurate than and at least as precise as any other age-based weight estimation rule: weight in kg=(3 × age last birthday)+5. It is accurate and precise in children <7 years old, but all age-based weight estimates are imprecise in older children. CONCLUSIONS: The Chinese Age Weight Rule should be used in a Chinese population in preference to any other age-based weight estimation rule. Caution should be taken when using it in older children in whom other weight-estimation tools may be more appropriate.

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.

Body fat measured by bioelectrical impedance in Hong Kong Chinese children.

OBJECTIVE: To establish reference standards for percentage body fat measured in Hong Kong Chinese children, by methods involving bioelectrical impedance analysis. DESIGN: Cross-sectional study. SETTING: Thirty-six randomly selected primary and secondary schools and a teaching hospital in Hong Kong. PARTICIPANTS: A total of 14 842 students randomly selected from the schools and two additional small convenience samples of subjects. MAIN OUTCOME MEASURES: Percentage body fat was measured with the Tanita Body Composition Analyzer (Model no. BF-522) and percentile curves were constructed using the LMS method. In one separate small sample of children, repeatability of the percentage body fat measurement was assessed at different times of the day by BF-522 bioelectrical impedance analysis. In another sample, assessment was by the BF-522 and two other models (BC-418 and BF-401) consecutively to test the agreement of percentage body fat values obtained by the three different models. RESULTS. The percentage body fat values and percentile curves are presented. From the age of 6 to 18 years, the percentage body fat remained fairly stable in boys, but increased steadily in girls. The mean difference in percentage body fat measured with BF-522 at different times of the day was around 1% (95% limits of agreement: -4% to +8%). The mean differences in readings obtained from the BC-418 and BF-522 devices were -3.5% and 1% in boys and girls, respectively. The 95% limits of agreement were particularly wide in boys (-15% to 8%). CONCLUSIONS: Reference values for percentage body fat of Chinese children and adolescents are provided. Caution needs to be exercised however, given that readings obtained at different times of the day vary and data obtained by different makes and models of bioelectrical impedance analysis machines may not be interchangeable.

Induced sputum inflammatory measures correlate with disease severity in children with obstructive sleep apnoea.

OBJECTIVE: To establish the association between airway inflammation and severity of obstructive sleep apnoea (OSA) in children. METHODS: Consecutive children presenting with symptoms suggestive of OSA were recruited. They completed a sleep apnoea symptom questionnaire, underwent physical examination, spirometry, sputum induction and an overnight polysomnography. Adequate sputum contained <50% squamous epithelial cells, and OSA was diagnosed if the obstructive apnoea index was >1. RESULTS: 73 children with a median (interquartile range (IQR)) age of 11.3 (10.0-13.2) years were recruited. There were 21 girls and the median body mass index of the group was 24.0 (18.0-27.0) kg/m2. The most common presenting symptoms were habitual snoring, mouth breathing and prone sleeping position. Sputum induction was successful in 43 (59%) children, of whom 14 were found to have OSA. Children with OSA had significantly greater percentage sputum neutrophil than those without OSA (18.5 (IQR 8.0-42.0) v 4 (IQR 3.0-11.3), p = 0.006). On multiple regression analysis, percentage sputum neutrophil was significantly associated with OSA (odds ratio = 1.1, p = 0.013). CONCLUSION: Children with OSA had airway inflammation characterised by a marked increase in neutrophils. Further studies are needed to confirm these findings and to better define the downstream cellular interactions and molecular pathogenesis in childhood OSA.

Insulin and obstructive sleep apnea in obese Chinese children.

OBJECTIVE: In adults, obstructive sleep apnea (OSA) is associated with insulin resistance and dyslipidemia. We aimed to establish correlation between OSA, serum lipid profile, and insulin levels in obese snoring children. METHODS: Consecutive obese children with habitual snoring were recruited. They underwent physical examination, overnight polysomnography (PSG), and metabolic studies. OSA was diagnosed if apnea hypopnea index (AHI) > 1.0, and cases were considered to have moderate to severe OSA if AHI > 10. RESULTS: Ninety-four obese subjects with habitual snoring were studied. Seventy-three subjects were male and the median age of the studied group was 12.0 years (IQR 9.7-13.9). None of the subjects had active cardiopulmonary disease, and the BMI values of our subjects were >95th percentile using local reference charts. Sixty subjects had OSA, 47 being mild, and 13 being moderate to severe OSA. Multiple logistic regression analysis revealed that saturation nadir and insulin levels were significantly associated with OSA. CONCLUSION: OSA is prevalent among obese children with habitual snoring and insulin is independently associated with the condition. Its role in the cardiovascular complications of childhood sleep apnea is worthy of further exploration.

Cough frequency in children with mild asthma correlates with sputum neutrophil count.

BACKGROUND: A study was undertaken to measure cough frequency in children with stable asthma using a validated monitoring device, and to assess the correlation between cough frequency and the degree and type of airway inflammation. METHODS: Thirty six children of median age 11.5 years (interquartile range (IQR) 9-14) with stable asthma were recruited. They underwent spirometric testing, exhaled nitric oxide (eNO) measurement, sputum induction for differential cell count, and ambulatory cough monitoring for 24 hours. Coughing episodes were counted both as individual spikes and as clusters. RESULTS: All children had mild intermittent asthma and their median forced expiratory volume in 1 second and eNO were 83.3% (IQR 81.1-97.6) and 56.1 ppb (IQR 37.4-105), respectively. The median number of cough episodes per day was 25.5 (IQR 16-42.8). Sputum induction was successful in 69% of the subjects and cough frequency was found to have a significant positive correlation with sputum neutrophil count (r = 0.833, p = 0.0001). CONCLUSIONS: Children with stable mild asthma have increased cough frequency that might be driven by a neutrophilic inflammatory pathway.

Limbs anthropometry of singleton Chinese newborns of 28-42 weeks' gestation.

Abnormalities of limbs are important features of some syndromes recognizable at birth. The purpose of this study was to establish normal standards of limbs including arm length, arm circumference, upper arm length, lower arm length, leg length, thigh circumference, upper leg length, and lower leg length. 10,226 infants (5,422 males, 4,804 females) with gestation 28-42 weeks from 12 hospitals were included. The LMS method using maximum penalized likelihood was used to perform model fitting of the anthropometric centiles for these parameters. This study provided the first set of references for the limbs of the infants by gestation and gender. Racial differences were found when comparing with other populations. The parameters are useful for evaluation of morphologic disorders involving the limbs.

Trunk anthropometry of Hong Kong Chinese infants.

BACKGROUND: Disturbed growth of the trunk may result in abnormal sternocostal relationship and a variety of pectus deformities. AIMS: The purposes of this study were to establish norms of trunk anthropometry for dysmorphology identification in the newborns and to evaluate chest circumference as a predictor for low birth weight for outborn infants where weighing scales were unavailable. STUDY DESIGN AND SUBJECTS: A total of 10,339 Chinese infants (5478 males, 4861 females) with gestation 24-42 weeks from 12 hospitals were included. The anthropometric measurements analyzed included chest circumference, inter-nipple distance, sternal length and abdominal circumference. OUTCOME MEASURES: The LMS method using maximum penalized likelihood was used to perform model fitting of the anthropometric centiles for these physical parameters. RESULTS: References tables of the four physical parameters for newborns were constructed. Chest circumference showed the highest correlation with birth weight (male: r = 0.866, female: r = 0.883). The cut-off points for chest circumference of 295 (male) and 299 mm (female) were the best predictor for low birth weight. There were also racial differences in these parameters. When compared with French infants, Chinese newborns had smaller chest circumference. CONCLUSION: These physical parameters provide useful references and aid dysmorphology diagnosis in newborns of ethnic Chinese origin.

A survey of bathing and showering practices in children with atopic eczema.

We evaluated the emollient use and bathing habits of children with atopic eczema (AE) managed at the paediatric dermatology clinic of a university teaching hospital, using children with noneczematous skin diseases as controls. Disease severity of AE in the preceding 12 months was evaluated by the Nottingham Eczema Severity Score. Three-quarters of patients with or without eczema preferred showering to bathing. Patients with AE were more likely to use bath oils than soap and to use emollients after a bath/shower. Review cases, however, were more likely to take a shower and for a longer time (10-30 min) than first-visit eczema patients. These habits did not vary with season or disease severity. Emulsifying ointment was the most commonly used agent for the bath/shower. Most patients applied emollient immediately after a bath/shower. However there were still significant proportions of AE patients who used soap (40% of first-visit vs. 27% of review cases) and who did not apply emollients after a bath/shower (25% of first-visit vs. 23% of review cases). It is important to determine whether this problem is due to inadequate patient education or whether other factors lead to poor compliance.

The six-minute walk test in healthy children: reliability and validity.

The aim of this study was to assess the reliability and validity of the 6-min walk test (6MWT) in healthy children. Chinese secondary school students were randomly recruited. They attended the current authors' unit on two occasions, separated by 2 weeks. Physical examination and standardised maximum incremental exercise testing on a treadmill were performed on the first visit. Spirometry and 6MWT were carried out on the second visit. A randomly selected subgroup was invited to return for repeat 6MWT at an interval of 2-4 weeks. Seventy-eight subjects were recruited; however, four failed to achieve maximal effort on exercise test. The final group included 43 young females and the mean+/-sd age of the subjects was 14.2+/-1.2 yrs. Physical examination was unremarkable in all cases. The mean+/-sd per cent predicted forced expiratory volume in one second was 91.4+/-10.2%. Concurrent validity was demonstrated by good correlation between the 6-min walking distance and maximum oxygen uptake determined on the exercise treadmill. Test-retest reliability was undertaken in 52 subjects, and the intraclass correlation coefficient (95% confidence interval) was calculated as 0.94 (0.89-0.96). In addition, Bland and Altman plots demonstrated a high degree of repeatability. In healthy children, the 6-min walk test is a reliable and valid functional test for assessing exercise tolerance and endurance.