Maternal diet during pregnancy: an emerging risk factor for childhood asthma

Evaluation of: Willers SM, Wijga AH, Brunekreef B et al. Maternal food consumption during pregnancy and the longitudinal development of childhood asthma. Am. J. Respir. Crit. Care Med. 178, 124–131 (2008).

It has been hypothesized that the recent marked increase in the prevalence of asthma may, in part, be a consequence of changing diet. There is increasing interest in the possibility that childhood asthma may be influenced by maternal diet during pregnancy and an increasing number of studies have highlighted associations between childhood asthma and maternal intake of certain foods (e.g., fish, fruits and vegetables) and nutrients (e.g., vitamin E, vitamin D, zinc and polyunsaturated fatty acids) during pregnancy. Maternal diet during pregnancy has the potential to influence fetal immune and airway development during a critical period of life with long-term irreversible consequences, such as childhood asthma. Further research, particularly intervention studies, needs to be carried out to establish whether dietary intervention during pregnancy can be used as a healthy, low-cost, public-health measure to reduce the prevalence of childhood asthma.     

Contributing factors to the development of childhood asthma: working toward risk minimization

Asthma is the most common chronic disease in childhood, and considerable research has been undertaken to find ways to prevent its development and reduce its prevalence. For such interventions to be successful, risk factors for asthma emergence should be identified and clearly defined. Data are robust for some of them, including atopy, viral infections and exposure to airborne irritants, whereas it is less conclusive for others, such as aeroallergen exposure and bacterial infections. Several interventions for asthma prevention, including avoidance and pharmacotherapy, have been attempted. However, most of them have furnished equivocal results. Various issues hinder the establishment of risk factors for asthma development and reduce the effectiveness of interventions, including the complexity of the disease and the fluidity of the developing systems in childhood. In this review, we revisit the evidence on pediatric asthma risk factors and prevention and discuss issues that perplex this field.     

The association between persistent eosinophilia and asthma in childhood is independent of atopic status

BACKGROUND: Although peripheral blood eosinophilia is associated with risk of asthma, the relation with atopy has not been established. OBJECTIVE: To assess the relationship between eosinophils and chronic asthma in childhood, and to determine the factors associated with eosinophil levels over time. METHODS: Percent eosinophils/300 white blood cell (WBC) count ('eos') was measured at 9 months, 6 years and 11 years in subjects participating in the prospective Tucson Children's Respiratory Study. Children were classified based on the number of measurements in which they had low (< or = 2%) or high (>5%) eosinophils, as follows: (1) Persistently low eos (n = 130); (2) Low eos (intermittently low or consistently moderate, but never high, n = 317); (3) Intermittently high eos (n = 192); and (4) Persistently high eos (n = 17). Only children with > or = 2 eos measurements were included in the analysis. Chronic asthma was defined as medical doctor (MD)-diagnosed asthma with reports of wheezing during the previous year, on > or = 3 questionnaires completed between 2 and 13 years of age. Children with at least one positive skin prick test (SPT; > or = 3 mm) at age 6 or 11 were considered 'atopic'. RESULTS: Chronic asthma was linearly related to longitudinally ascertained eosinophils (trend chi2 P<0.001) with prevalence ranging from 5.8% among children with persistently low eos to 37.5% among children with persistently high eos. This relation was independent of atopy. Parental history of asthma was associated with both chronic asthma (P <0.001) and with longitudinal eosinophil status (P < 0.001). After adjusting for atopy and gender, there was a 70% increase in asthma risk with each increase in longitudinal eosinophil level. This stepwise increase was reduced to 48% when parental asthma was added to the model. CONCLUSION: Longitudinal eosinophil levels are linearly associated with chronic asthma in childhood, independent of atopy. The strong association between parental asthma and eosinophil status suggests that genetic background may be an important determinant of eosinophilic response.     

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.     

Psychosocial risk factors for tobacco use among adolescents with asthma

OBJECTIVE: To determine the prevalence of smoking among adolescents with asthma and smoking's psychosocial risk factors (environmental smoking exposure, autonomy, depression). METHOD: Participants were 2,039 adolescents with asthma and 2,039 matched controls from the Add Health study. RESULTS: The prevalence of ever smoking among adolescents with asthma was 56%. Among ever smokers with asthma, the prevalence of current smoking was 48%, and the prevalence of current smokers having made a recent attempt to stop smoking was 57%. Having parents who have smoked, exposure to friends who smoke, and depression were significant psychosocial risk factors for ever smoking. Asthma and exposure to friends who smoke were significantly associated with current smoking, and attempts to stop smoking were significantly associated with asthma and depression. CONCLUSIONS: Psychosocial risk factors for smoking among adolescents with and without asthma appear similar. Research on the role of illness in tobacco control is warranted.     

Caesarean section increases the risk of hospital care in childhood for asthma and gastroenteritis

OBJECTIVE: To investigate if caesarean section (CS) increases the risk for childhood asthma and gastroenteritis with reference made to children born with vaginal delivery (VD). METHODS: Retrospective study of data from linked Swedish medical service registers--Medical Birth Registry (MBR) and Hospital Discharge Registry (HDR). Data were obtained from women without any background/perinatal morbidity noted, and from children without any neonatal complications. Children that had reached at least 1 year of age and were found in the HDR were considered as cases, whereas children not found in the HDR or hospitalized for other causes than asthma or gastroenteritis were defined as controls. Odds ratios (OR) stratified for year of birth, maternal age, parity and smoking in early pregnancy were calculated. Investigations were made comparing the risk for in hospital treatment for asthma or gastroenteritis in CS children and in VD siblings of CS children. The overall inpatient morbidity in CS and VD children were also investigated. RESULTS: The OR for asthma in CS children was 1.31 [95% confidence interval (CI) 1.23-1.40]. The same OR, 1.31, was found for gastroenteritis (95% CI 1.24-1.38). The OR for CS children having experienced both asthma and gastroenteritis was further increased (1.74, 95% CI 1.36-2.23). The risk for asthma in VD siblings of CS children was not significantly increased, whereas VD siblings experienced a slightly increased risk for gastroenteritis. CS children had an increased overall in hospital morbidity when compared to VD children. CONCLUSION: There is a significant increase of the risk for developing symptoms of asthma and/or gastroenteritis that motivates admission for hospital care in CS children older than 1 year. It is speculated that a disturbed intestinal colonization pattern in CS children may be a common pathogenic factor.     

Brief report: social risk factors predict cigarette smoking progression among adolescents with asthma

OBJECTIVE: To compare smoking progression in adolescents with and without asthma and to compare their psychosocial risk factors. METHODS: Participants were 1,507 adolescents with asthma and 1,507 healthy matched controls from Waves I and II of the Add Health Project assessed at baseline and again 1 to 2 years later at follow-up. Three levels of smoking progression (defined as smoking more frequently and/or intensely over time) were identified: (a) Late Experimenters (never smokers at baseline, ever smokers at follow-up), (b) Early Experimenters (ever smokers at baseline, current/current frequent smokers at follow-up), and (c) Early Smokers (current smokers at baseline, current frequent smokers at follow-up). RESULTS: Twenty percent of adolescents experienced progression in their smoking behavior; those with and without asthma were equally likely to progress. Among adolescents who progressed, 37% were Late Experimenters, 42% were Early Experimenters, and 21% were Early Smokers. Exposure to friends who smoked was a consistent and powerful social risk factor for smoking progression among adolescents with asthma-more so than among adolescents without asthma. This effect was intensified among Late Experimenters by the presence of a positive history of parent smoking. CONCLUSIONS: Findings underscore the importance of addressing cigarette smoking behavior and its social risk factors among adolescents with asthma in both clinical and public health contexts, during early adolescence, and through research on this topic.     

Time trends in asthma and wheeze in Swedish children 1996–2006: prevalence and risk factors by sex

Background:  Recent data suggest that the previously rising trend in childhood wheezing symptoms has plateaued in some regions. We sought to investigate sex-specific trends in wheeze, asthma, allergic conditions, allergic sensitization and risk factors for wheeze.
Methods:  We compared two population-based cohorts of 7 to 8-year olds from the same Swedish towns in 1996 and 2006 using parental expanded ISAAC questionnaires. In 1996, 3430 (97%) and in 2006, 2585 (96%) questionnaires were completed. A subset was skin prick tested: in 1996, 2148 (88%) and in 2006, 1700 (90%) children participated.
Results:  No significant change in the prevalence of current wheeze ( P  = 0.13), allergic rhinitis ( P  = 0.18) or eczema ( P  = 0.22) was found despite an increase in allergic sensitization (20.6–29.9%, P  < 0.01). In boys, however, the prevalence of current wheeze (12.9–16.4%, P  < 0.01), physician-diagnosed asthma (7.1–9.3%, P  = 0.03) and asthma medication use increased. In girls the prevalence of current symptoms and conditions tended to decrease. The prevalence of all studied risk factors for wheeze and asthma increased in boys relative to girls from 1996 to 2006, thus increasing the boy-to-girl prevalence ratio in risk factors.
Conclusions:  The previously reported increase in current wheezing indices has plateaued in Sweden. Due to increased diagnostic activity, physician diagnoses continue to increase. Time trends in wheezing symptoms differed between boys and girls, and current wheeze increased in boys. This was seemingly explained by the observed increases in the prevalence of risk factors for asthma in boys compared with girls. In contrast to the current symptoms of wheeze, rhinitis or eczema, the prevalence of allergic sensitization increased considerably.     

Perinatal factors and atopic disease in childhood

Background Recent work has suggested possible linkages between perinatal factors and notably, head circumference and risks of subsequent atopic illness. Objective To examine the linkages between perinatal factors and risks of atopic conditions in a birth cohort of New Zealand children studied to the age of 16. Methods Measures of atopic illness including asthma, eczema, and other allergies were assessed prospectively during the course of a 16 year longitudinal study of a birth cohort of 1265 New Zealand children. In the initial stage of this research, measures of perinatal variables including birthweight, gestational age, head circumference and length at birth were obtained from hospital record data. Results Children with head circumference at birth of 37 cm or greater had (unadjusted) odds of asthma that were 1.8 (P < 0.01) to 3.0 (P < 0.0001) times higher than the odds for children of lesser head circumference. However, risks of asthma were not related to other perinatal measures including birthweight, gestational age or length or ratios of these measures. There were no consistent associations between perinatal measures and other measures of childhood atopy including eczema, allergic rhinitis and other allergies. The associations between head circumference and asthma risks persisted when due allowance was made for potentially confounding social and perinatal factors. Conclusions It is concluded that large head circumference at birth may be associated with increased risks for the development of asthma. Possible explanations for the linkages between head circumference and asthma risks are considered.     

Passive smoking and childhood asthma

Passive exposure to tobacco smoke was assessed in children with asthma (age 3-15) and in referents. There was statistically significantly (P less than 0.0005) higher excretion of the nicotine metabolite, cotinine, in the urine of 49 children with asthma (geometric mean 10 ng/ml) compared with 77 referents (4.8 ng/ml). Maternal smoking was statistically significantly more prevalent among the asthmatics than among the referents (relative risk = RR = 2.6, 95% C1 = 1.2-5.3). In conclusion, the exposure to environmental tobacco smoke in asthmatic children was higher than among healthy children, indicating that passive smoking may be a predisposing and/or aggravating factor for childhood asthma.     

Prevalence of childhood asthma in Istanbul, Turkey

ÖneşÜ. Sapan N, Somer A, Dişçi R, Salman N, Güler N, Yalçm I. Prevalence of childhood asthma in Istanbul, Turkey.
In order to determine the asthma prevalence in 6–12-year-old schoolchildren in Istanbul, we issued 2350 questionnaires, according to ISAAC criteria, in six randomly selected city primary schools to be completed at home by parents. A total of 2232 of the questionnaires were completed, an overall response rate of 94.9%, and 2216 questionnaires were taken into consideration. The prevalence of asthma was found to be 9.8% and wheezing 15.1%. To investigate the effect of socioeconomic status on the prevalence of asthma, we evaluated the heating system at home, the place of residence, the educational levels of the mother and father, the number of people living in the house, the sharing of bedrooms, and the annual family income. In conclusion, the prevalence of childhood asthma was not affected by any of these factors. Atopic family history, food allergy, eczema, and frequent otitis media and sinusitis attacks were evaluated and found to be significant in asthma prevalence.