Symptoms of asthma and atopic disorders in preschool children: prevalence and risk factors.

BACKGROUND: Published epidemiological data suggested that asthma and allergies may be increasing in preschool children. Identification of the risk factors is important for planning possible early intervention to prevent asthma. This study was designed to measure the prevalence of, and risk factors for, asthma and atopic disorders in preschool children from Hong Kong. METHODS: Children aged 2-6 years living in Hong Kong were recruited through the local nurseries and kindergartens for this study to ascertain the presence of symptoms of asthma and various possible risk factors. The parental questionnaire was developed based on the International Study of Asthma and Allergies in Childhood questionnaire. RESULTS: A total of 3089 children (1506 boys) from 14 nurseries and kindergartens participated in this study. The prevalence of wheeze ever and current wheeze were 16.7% and 9.3%. Two hundred and thirty-four subjects were born in mainland China and migrated to Hong Kong subsequently. When compared with children born and raised in Hong Kong, children born in mainland China had significantly lower prevalence of current wheeze (3.4% vs. 9.6%, P<0.01). Two environmental factors in the first year of life were associated with wheezing attacks within the last 12 months. They were the use of foam pillow (Odds ratio: 1.45; 95% Confidence interval: 1.04-2.00) and the use of gas as cooking fuel (1.68; 1.03-2.75). Frequent use of paracetamol was also associated with wheezing attack in the past 12 months. CONCLUSIONS: This study confirms the high prevalence of symptoms of atopic disorders in preschool children from Hong Kong. Early environmental exposure factors are important determinants of subsequent development of asthma symptoms in the preschool years. Further studies are needed to evaluate the possible pathogenetic role of the identified risk factors.

Asthma and atopy are associated with DEFB1 polymorphisms in Chinese children.

Human beta-defensin (HBD)-1 is constitutively expressed in the airway, and hBD-1 plays crucial roles in innate immunity against respiratory pathogens. Asthma was associated with DEFB1 polymorphisms in Caucasians. This study investigates whether three single nucleotide polymorphisms (SNPs) in 5'-untranslated region of DEFB1 are associated with asthma phenotypes in Chinese children. Subjects aged 5-18 years were recruited from general pediatric clinics. Plasma IgE concentrations were measured by immunoassays. DEFB1 SNPs were characterized by restriction fragment length polymorphism. In all, 305 asthmatics and 156 controls were recruited. For asthma diagnosis, atopy and plasma total IgE, higher percentages of subjects with these outcomes had the minor alleles -20A and -52G (P = 0.041-0.0002). For log-transformed total IgE, the covariate was positive and significant for G-20A under recessive model (P = 0.001) and for G-52A under both recessive and codominant models (P = 0.008 and 0.035). The recessive model covariate was also positive and significant (P = 0.020) for C-44G on peripheral blood eosinophil count. The GCA haplotype of DEFB1 was significantly associated with asthma (odds ratio (95% confidence interval): 1.64 (1.05-2.57); P = 0.029). These results suggest that DEFB1 is a candidate gene for asthma and atopy in children.

Nitric oxide synthase polymorphisms and asthma phenotypes in Chinese children.

BACKGROUND: Nitric oxide (NO) is a key factor for balancing T-helper type 1/T-helper type 2 immunity. Single nucleotide polymorphisms (SNPs) in nitric oxide synthase (NOS) genes have been associated with atopy and exhaled NO concentrations in Caucasians. We investigated the association between asthma traits and genetic polymorphisms in neuronal NO synthase (NOS1) and endothelial NO synthase (NOS3) in Chinese children. METHODS: Asthmatic children between 5 and 18 years of age and non-allergic controls were recruited. Plasma total IgE was measured by microparticle immunoassay, whereas allergen-specific IgEs were measured by fluorescent enzyme immunoassay. Fractional exhaled NO concentration (FeNO) was measured by a chemiluminescence analyser. NOS1 C5266T and NOS3 G894T were genotyped by restriction fragment length polymorphism, and (AAT)n polymorphism in intron 20 of NOS1 was determined by GeneScan analysis. RESULTS: The mean (SD) ages of 295 asthmatics and 174 controls were 11.1 (3.8) years and 11.6 (4.0) years, respectively (P=0.162). NOS1 C5266T and NOS3 G894T were not associated with asthma, atopy or FeNO. However, significantly more subjects with T/T in NOS1 C5266T had increased plasma total IgE as compared with those with C/T or C/C (P=0.017). This SNP was also associated with sensitization to Dermatophagoides pteronyssinus (P=0.049). Among asthmatic patients, log-transformed plasma total IgE levels were significantly higher among those homozygous for 5266T of NOS1 [mean (SD): 2.84 (0.44) for T/T, 2.68 (0.42) for C/T, 2.59 (0.69) for C/C; P=0.021]. This study found a significant inter-ethnic difference in the allele frequencies of AAT repeats, and this polymorphism was associated with high plasma total IgE levels (P=0.044) but not FeNO (P=0.158). NOS3 G894T was not associated with any asthma or atopy phenotype. CONCLUSIONS: NOS1 C5266T and AAT repeats affect plasma IgE concentrations in Chinese children. On the other hand, neither NOS1 nor NOS3 SNP was associated with FeNO or the risk of having asthma.

High levels and gender difference of exhaled nitric oxide in Chinese schoolchildren.

BACKGROUND: Exhaled nitric oxide (eNO) may represent a useful noninvasive marker of airway inflammation, but data on the reference population values in schoolchildren are limited. No reference eNO study in Asian children has been published. METHODS: Levels of eNO in a sample of 531 schoolchildren aged 11-18 years recruited from five schools (three international schools) in Hong Kong were measured online by a chemiluminescence analyser according to ERS/ATS standard. Each student also completed an International Study of Asthma and Allergic disease in Childhood questionnaire. RESULTS: Among the children without a physician's diagnosis of asthma or symptoms of wheeze, rhinitis and eczema, there were 258 Chinese and 33 Caucasians. In control Chinese children, the eNO level (median: interquantile range) was significantly higher (P<0.001) in males (17.0 parts per billion (p.p.b.); 10.7-36.6) than in females (10.8 p.p.b.; 7.8-17.6). When compared with Caucasian control males (11.6 p.p.b.; 8.2-19.3) and females (9.1 p.p.b.; 7.5-11.9), the Chinese children had significantly higher eNO levels for both males (P=0.011) and females (P=0.037). For Chinese asthmatic males, the median eNO (interquartile range) was 39.8 p.p.b. (12.5-73.8), and for asthmatic females, 18.0 (9.6-56.3). After controlling for sex in Chinese controls, eNO did not have any significant correlation with height, weight and body mass index or body surface area. CONCLUSIONS: This study demonstrates a gender difference of eNO level in healthy Chinese schoolchildren. When compared with Caucasians, Chinese children have significantly higher eNO levels.

Hepatic steatosis in obese Chinese children.

THE AIMS OF OUR STUDY WERE: (1) to determine the prevalence of asymptomatic hepatic steatosis and presumed nonalcoholic steatohepatitis, in our local population of obese Chinese children referred for medical assessment; and (2) to assess the correlation between severity of ultrasonographic hepatic steatosis and degree of obesity, insulin resistance and serum biochemical abnormalities. DESIGN: Cross-sectional study. METHODS: In total, 84 obese children, 25 girls and 59 boys with median age and body mass index (BMI) of 12.0 years (interquartile range (IR): 9.5-14.0) and 30.3 kg/m(2) (IR: 27.1-33.4), respectively, referred for medical assessment were studied. All subjects underwent physical examination, anthropometric and dual energy X-ray absorptiometry (DEXA) scan measurements and real-time ultrasonographic (US) examination of the liver. Fasting blood samples were collected for the measurement of liver function, hepatitis status, levels of serum glucose and insulin and lipid profile. Degree of fatty infiltration of the liver was graded according to ultrasonic appearance of liver echotexture, liver-diaphragm differentiation in echo amplitude, hepatic echo penetration and clarity of hepatic blood vessels. RESULTS: All recruited subjects had no history of alcohol abuse and tests for Hepatitis B or C virus were negative. Thorough examination showed all of them to be in general good health without signs of chronic liver disease. Hepatic steatosis identified by defined ultrasonic appearances was diagnosed in 65 subjects (77%); 17 girls and 48 boys. The severity of fatty liver was positively related to anthropometric measurements including BMI, waist and hip circumference, subscapular skinfold thickness; insulin resistance markers [QUICKI and homeostasis model assessment (HOMA)], and hypertriglyceridaemia. Multvariate ordinal regression analysis showed that BMI and raised alanine aminotransferase (ALT) were positively associated with fatty liver. Combination of hepatic steatosis with raised ALT (presumptive NASH) was found in 19 subjects (24%). This group of patients had significantly higher waist hip ratio and conicity index compared to those with isolated hepatic steatosis. Boys with presumed NASH were also found to have significantly higher insulin resistance. CONCLUSION: Nonalcoholic fatty liver disease (NAFLD) was common among our cohort of obese children referred for medical assessment. The prevalence of simple steatosis and presumed NASH was 77 and 24%, respectively. The severity of US steatosis was positively correlated with BMI, raised ALT, insulin resistance and hypertryglyceridaemia. Ultrasonography being noninvasive and readily available could be used for the monitoring of the progression of hepatic steatosis. Further longitudinal studies are required to determine the natural disease progression and the role of insulin resistance and other factors in the pathophysiology of NAFLD.