OBJECTIVE:We sought to study arterial endothelial function and carotid intima-media thickness (IMT), both early markers of atherosclerosis, in overweight compared to normal children. DESIGN: Case-control comparison. SUBJECTS: A total of 36 asymptomatic overweight children (body mass index (BMI)423; mean 2573) aged 9-12 y and 36 age-and gender-matched nonobese healthy children (BMIo21) from a school community. MEASUREMENTS: The key parameters were: BMI, arterial endothelial function (ultrasound-derived endothelium-dependent dilation) and carotid artery IMT. The secondary parameters measured included body fat content, waist-hip ratio (WHR), blood pressures, blood lipids, insulin and glucose. RESULTS: The two groups were well matched for blood pressures, cholesterol and glucose levels, but BMI (Po0.0001), body fat (P ¼ 0.001), WHR (Po0.05), fasting blood insulin (P ¼ 0.001) and triglyceride levels (Po0.05) were higher in obese children. Overweight was associated with impaired arterial endothelial function (6.672.3 vs 9.773.0%, Po0.0001) and increased carotid IMT (0.4970.04 mm vs 0.4570.04 mm, P ¼ 0.006). The degree of endothelial dysfunction correlated with BMI (Po0.003) on multivariate analysis. CONCLUSION: Obesity, even of mild-to-moderate degree, is independently associated with abnormal arterial function and structure in otherwise healthy young children.

Background: Childhood obstructive sleep apnoea (OSA) is increasingly being recognised. Its effects on blood pressure (BP) elevation and hypertension are still controversial. Objective: To evaluate the association between OSA and ambulatory BP in children. Methods: Children aged 6-13 years from randomly selected schools were invited to undergo overnight sleep study and ambulatory BP monitoring after completing a validated OSA questionnaire. OSA was diagnosed if the obstructive apnoea-hypopnoea index (AHI) was .1, and normal controls had AHI ,1 and snoring ,3 nights per week. Children with OSA were subdivided into a mild group (AHI 1-5) and moderate to severe group (AHI .5). Results: 306 subjects had valid sleep and daytime BP data. Children with OSA had significantly higher BP than normal healthy children during both sleep and wakefulness. BP levels increased with the severity of OSA, and children with moderate to severe disease (AHI .5) were at significantly higher risk for nocturnal systolic (OR 3.9 (95% CI 1.4 to 10.5)) and diastolic (OR 3.3 (95% CI 1.4 to 8.1)) hypertension. Multiple linear regression revealed a significant association between oxygen desaturation index and AHI with daytime and nocturnal BP, respectively, independent of obesity. Conclusions: OSA was associated with elevated daytime and nocturnal BP, and is an independent predictor of nocturnal hypertension. This has important clinical implications as childhood elevated BP predicts future cardiovascular risks. Future studies should examine the effect of therapy for OSA on changes in BP.In adults, obstructive sleep apnoea (OSA) is an independent risk factor for hypertension and is involved in the initiation and progression of other cardiovascular diseases.1-3 However, corresponding data for the paediatric population are scarce, and the few published studies have provided conflicting results. [4][5][6][7][8][9] Marcus and colleagues 4 suggested that children with OSA had higher daytime and nocturnal diastolic blood pressure (BP) compared with primary snorers, whereas Amin and colleagues 5 found lower diastolic BP among children with OSA. Guilleminault and colleagues 6 demonstrated that a subgroup of children with OSA were hypotensive rather than hypertensive. Kohyama and colleagues 7 found a positive correlation between both nocturnal systolic and diastolic BP with severity of OSA and, similarly, Enright and colleagues 8 found respiratory disturbance index to be significantly associated with systolic and diastolic BP. A recent study, however, failed to confirm such a positive association.9 These inconsistent findings in BP measurements might have been related to the small sample sizes and lack of normal healthy subjects for comparison. A recent meta-analysis concluded that there was inadequate evidence for an increased risk of elevated BP in children with OSA. The authors also found marked heterogeneity among published series and emphasised the need for further studies to clarify this important issue.

Background-The prevalence of obesity in both adults and children is increasing rapidly. Obesity in children is independently associated with arterial endothelial dysfunction and wall thickening, key early events in atherogenesis that precede plaque formation. Methods and Results-To evaluate the reversibility of obesity-related arterial dysfunction and carotid intima-media thickening by dietary and/or exercise intervention programs, 82 overweight children (body mass index, 25Ϯ3), 9 to 12 years of age, were randomly assigned to dietary modification only or diet plus a supervised structured exercise program for 6 weeks and subsequently for 1 year. The prospectively defined primary end points were ultrasound-derived arterial endothelial function (endothelium-dependent dilation) of the brachial artery and intima-media thickness of common carotid artery. At 6 weeks, both interventions were associated with decreased waist-hip ratio (PϽ0.02) and cholesterol level (PϽ0.05) as well as improved arterial endothelial function. Diet and exercise together were associated with a significantly greater improvement in endothelial function than diet alone (Pϭ0.01). At 1 year, there was significantly less thickening of the carotid wall (PϽ0.001) as well as persistent improvements in body fat content and lipid profiles in the group continuing an exercise program. Vascular function was significantly better in those children continuing exercise (nϭ22) compared with children who withdrew from the exercise program (nϭ19) (PϽ0.05). Conclusions-Obesity-related vascular dysfunction in otherwise healthy young children is partially reversible with diet alone or particularly diet combined with exercise training at 6 weeks, with sustained improvements at 1 year in those persisting with diet plus regular exercise.

Background: Body mass index (BMI) and waist circumference (WC) correlate with cardiovascular (CV) risk factors in childhood which track into adulthood. WC provides a measure of central obesity, which has been specifically associated with CV risk factors. Reference standards for WC, and for WC and BMI risk threshold values are not established in Chinese children. Objectives: To construct reference percentile charts of WC, establish relationships between WC, BMI and other risk factors, and propose WC and BMI threshold values predictive of CV risk factors in Hong Kong ethnic Chinese children. Methods: Weight, height, waist and hip circumference were measured in 2593 (52% boys, 47% girls) randomly sampled Hong Kong school children aged 6-12 years. In 958 of these and 97 additional overweight children (n ¼ 1055), the relationships between WC, BMI, waist/hip and waist/height ratio and six age-adjusted CV risk factors (485% percentile levels of blood pressure (BP), fasting triglycerides, low-density lipoprotein (LDL) cholesterol, glucose and insulin levels, and o15% percentile levels of high-density lipoprotein (HDL) cholesterol) were studied. Receiver-operating characteristic analysis was employed to derive optimal age-adjusted sex-specific WC and BMI thresholds for predicting these measures of risk. Results: WC percentiles were constructed. WC correlated slightly more than BMI with CV risk factors and most strongly with insulin and systolic BP, but poorly or not with LDL and glucose. Optimal WC and BMI risk thresholds for predicting four of these six CV risk factors were ca. the 85th percentiles (sensitivities B0.8, specificities B0.87) with age-specific cutoff values in girls/ boys from B57/58 to B71/76 cm and 17/18 to 22/23 kg/m 2 . Conclusion: These are the first set of WC reference data for Chinese children. WC risk cutoff values are proposed which, despite a smaller waist in Chinese children, are similar to those reported for American children. WC percentiles may reflect population risk.

Background: Central body fat is a better predictor than overall body fat for cardiovascular (CV) risk factors in both adults and children. Waist circumference (WC) has been used as a proxy measure of central body fat. Children at high CV risk may be identified by WC measurements. Waist-to-height ratio (WHTR) has been proposed as an alternative, conveniently age-independent measure of CV risk although WHTR percentiles have not been reported. We aim to provide ageand sex-specific reference values for WC and WHTR in Hong Kong Chinese children.

There is increasing evidence suggesting that the cut-off values for defining obesity used in the Western countries cannot be readily applied to Asians, who often have smaller body frames than Caucasians. We examined the BMI and body fat (BF) as measured by bioelectrical impedance in 5153 Hong Kong Chinese subjects. We aimed to assess the optimal BMI reflecting obesity as defined by abnormal BF in Hong Kong Chinese. Receiver operating characteristic curve (ROC) analysis was used to assess the optimal BMI predicting BF at different levels. The mean age and SD of the 5153 subjects (3734 women and 1419 men) was 51´5 (SD 16´3) years (range: 18´0±89´5 years, median: 50´7 years). Age-adjusted partial correlation (r) between BMI and BF in women and men were 0´899 P , 0´001 and 0´818 P , 0´001 respectively. Using ROC analysis, the BMI corresponding to the conventional upper limit of normal BF was 22´5±23´1 kg/m 2 , and the BMI corresponding to the 90 percentiles of BF was 25´4±26´1 kg/m 2 . Despite similar body fat contents, the BMI cut-off value used to define obesity in Hong Kong Chinese should be lower as compared to Caucasians. We suggest a BMI of 23 kg/m 2 and 26 kg/m 2 as the cut-off values to define overweight and obesity respectively in Hong Kong Chinese.

Aims-(1) To validate a leg to leg bioimpedance analysis (BIA) device in the measurement of body composition in children by assessment of its agreement with dual energy x ray absorptiometry (DXA) and its repeatability. (2) To establish a reference range of percentage body fat in Hong Kong Chinese children. Methods-Sequential BIA and DXA methods were used to determine body composition in 49 children aged 7-18 years; agreement between the two methods was calculated. Repeatability for the BIA method was established from duplicate measurements. Body composition was then determined by BIA in 1139 girls and 1243 boys aged 7-16 years, who were randomly sampled in eight local primary and secondary schools to establish reference ranges. Results-The 95% limits of agreement between BIA and DXA methods were considered acceptable (−3.3 kg to −0.5 kg fat mass and −3.9 to 0.6% body fat). The percentage body fat increased with increasing age. Compared to the 1993 Hong Kong growth survey, these children had higher body mass index. Mean (SD) percentage body fat at 7 years of age was 17.2% (4.4%) and 14.0% (3.4%) respectively for boys and girls, which increased to 19.3% (4.8%) and 27.8% (6.3%) at age 16. Conclusion-Leg

Aims: To evaluate effects of a low energy diet, with or without strength training, on blood lipid profile in obese children. Methods: Eighty two obese children were enrolled into a six week dietary programme, and were randomly allocated to a training group or a non-training group. The training group underwent regular exercise sessions with emphasis on strength training. Results: Height increased significantly, with a non-significant reduction in body mass index. Fat free mass increased significantly in the training group. Serum total cholesterol was significantly reduced in both groups. The LDL:HDL ratio significantly decreased in the training group. Conclusion: Results support the potentially beneficial effects of both diet and physical training. Further and longer term evaluation of such programmes is required.