Daycare attendance, asthma and atopy

Is the Association of Early Day Care Attendance with Childhood Asthma Explained by Underlying Susceptibility?

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Background:

Previous studies of early day care attendance and asthma development are inconsistent, which may be explained by inadequate control of confounding and effect modification. We examined the effect of early day care on the risk of asthma taking into account the underlying susceptibility to asthma.

Methods:

The study included 55,404 children participating in the Norwegian Mother, Father and Child Cohort Study. Asthma at age 7 was defined by dispensed asthma medications in the Norwegian Prescription Database. We defined a disease risk score (DRS) to account for an underlying susceptibility to asthma including a range of hereditary and nonhereditary predictors of asthma. We assessed confounding and modifying effects of DRS on the association between day care and asthma.

Results:

Day care before 18 months was associated with a lower risk of asthma by age 7 (adjusted risk ratio [RR] = 0.85; 95% confidence interval [CI] = 0.78, 0.92) when compared with home care. DRS modified the estimated effect of day care on asthma risk. Among the 80% of children with DRS between 0.03 and 0.16, day care was associated with a reduced asthma risk (RRs between 0.79 and 0.87), whereas among 0.5% of children with a high DRS (above 0.28), estimated effect of day care on asthma increased gradually (RR for the highest DRS 2.2; 1.0–4.9).

Conclusions:

In our study, among most children, early day care was associated with reduced asthma risk at 7 years, and increased risk in a small group of children with very high underlying susceptibility to asthma.

Factors associated with asthma expression in adolescents

Objective:

To evaluate risk factors associated with asthma symptoms in adolescents in the 13- to 14-year age bracket.

Methods:

This was a cross-sectional study involving adolescents enrolled in randomly selected public schools in the city of Belo Horizonte, Brazil, and conducted with the use of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire and its supplementary module for risk factor assessment. The ISAAC questionnaire was completed by the students themselves, whereas the supplementary questionnaire was completed by their parents or legal guardians. Variables showing p ≤ 0.25 in the univariate analysis were included in the multivariate analysis. Stepwise regression with backward elimination was used for variable selection.

Results:

We evaluated 375 adolescents, 124 (33.1%) of whom had asthma symptoms. The final multivariate analysis model revealed that asthma symptoms were associated with birth weight < 2,500 g (p < 0.001), day care center or nursery attendance (p < 0.002), maternal history of asthma (p < 0.001), contact with animals during the first year of life (p < 0.027), current contact with animals outside the home (dogs, cats, or farm animals; p < 0.005), and more than 20 cigarettes per day smoked by parents or other household members (p < 0.02).

Conclusions:

Exposure to animals in and outside the home is associated with asthma symptoms, as is environmental tobacco smoke exposure. Families, health professionals, and administrators of health care facilities should take that into account in order to prevent asthma and reduce asthma morbidity.

Virus-induced modulation of lower airway diseases: pathogenesis and pharmacologic approaches to treatment

Uncomplicated upper respiratory viral infections are the most common cause of days lost from work and school and exert a major economic burden. In susceptible individuals, however, common respiratory viruses, particularly human rhinoviruses, also can have a major impact on diseases that involve the lower airways, including asthma, chronic obstructive pulmonary diseases (COPD) and cystic fibrosis (CF). Respiratory virus-induced wheezing illnesses in early life are a significant risk factor for the subsequent development of asthma, and virus infections may also play a role in the development and progression of airway remodeling in asthma. It is clear that upper respiratory tract virus infections can spread to the lower airway and trigger acute attacks of asthma, COPD or CF. These exacerbations can be life-threatening, and exert an enormous burden on health care systems. In recent years we have gained new insights into the mechanisms by which respiratory viruses may induce acute exacerbations of lower airway diseases, as well as into host defense pathways that may regulate the outcomes to viral infections. In the current article we review the role of viruses in lower airway diseases, including our current understanding on pathways by which they may cause remodeling and trigger acute exacerbations. We also review the efficacy of current and emerging therapies used to treat these lower airway diseases on the outcomes due to viral infection, and discuss alternative therapeutic approaches for the management of virus-induced airway inflammation.

Childhood asthma-predictive phenotype

Wheezing is a fairly common symptom in early childhood, but only some of these toddlers will experience continued wheezing symptoms in later childhood. The definition of the asthma-predictive phenotype is in children with frequent, recurrent wheezing in early life who have risk factors associated with the continuation of asthma symptoms in later life. Several asthma-predictive phenotypes were developed retrospectively based on large, longitudinal cohort studies; however, it can be difficult to differentiate these phenotypes clinically as the expression of symptoms, and risk factors can change with time. Genetic, environmental, developmental, and host factors and their interactions may contribute to the development, severity, and persistence of the asthma phenotype over time. Key characteristics that distinguish the childhood asthma-predictive phenotype include the following: male sex; a history of wheezing, with lower respiratory tract infections; history of parental asthma; history of atopic dermatitis; eosinophilia; early sensitization to food or aeroallergens; or lower lung function in early life.

Influence of poverty and infection on asthma in Latin America

PURPOSE OF REVIEW

Asthma in Latin America is a growing public health problem and seems to be most prevalent and cause most morbidity among poor urban populations. This article will review the findings of recent human studies of the associations of asthma prevalence in Latin America with factors associated with poverty and inequality including childhood infections, stress, environment, nutrition and diet.

RECENT FINDINGS

Most asthma in childhood in Latin America is nonatopic and has been associated with exposures related to environmental dirt, diet and psychosocial distress. These factors are strongly linked to poverty and inequality. Interestingly, infections with bacterial, viral and parasitic pathogens in childhood appear to attenuate atopy in childhood but have no effect on asthma symptoms. There are biologically plausible mechanisms by which dirt exposures (e.g. endotoxin and other microbial products and nonmicrobial irritants), diet and obesity and psychosocial stress may cause airways inflammation.

SUMMARY

Most childhood asthma in Latin America is nonatopic for which important risk factors are those of poverty including poor hygiene (i.e. dirt), poor diet and obesity and psychosocial stress. There is evidence that exposures to infections in early childhood reduce atopy but not asthma. Research is needed to identify causes of nonatopic asthma that may be suitable for primary prevention or other public health intervention strategies for asthma in Latin America.

The genetics of asthma and allergic disease: a 21st century perspective

Asthma and allergy are common conditions with complex etiologies involving both genetic and environmental contributions. Recent genome-wide association studies (GWAS) and meta-analyses of GWAS have begun to shed light on both common and distinct pathways that contribute to asthma and allergic diseases. Associations with variation in genes encoding the epithelial cell-derived cytokines, interleukin-33 (IL-33) and thymic stromal lymphopoietin (TSLP), and the IL1RL1 gene encoding the IL-33 receptor, ST2, highlight the central roles for innate immune response pathways that promote the activation and differentiation of T-helper 2 cells in the pathogenesis of both asthma and allergic diseases. In contrast, variation at the 17q21 asthma locus, encoding the ORMDL3 and GSDML genes, is specifically associated with risk for childhood onset asthma. These and other genetic findings are providing a list of well-validated asthma and allergy susceptibility genes that are expanding our understanding of the common and unique biological pathways that are dysregulated in these related conditions. Ongoing studies will continue to broaden our understanding of asthma and allergy and unravel the mechanisms for the development of these complex traits.

The development of socio-economic health differences in childhood: results of the Dutch longitudinal PIAMA birth cohort

BACKGROUND

People with higher socio-economic status (SES) are generally in better health. Less is known about when these socio-economic health differences set in during childhood and how they develop over time. The goal of this study was to prospectively study the development of socio-economic health differences in the Netherlands, and to investigate possible explanations for socio-economic variation in childhood health.

METHODS

Data from the Dutch Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study were used for the analyses. The PIAMA study followed 3,963 Dutch children during their first eight years of life. Common childhood health problems (i.e. eczema, asthma symptoms, general health, frequent respiratory infections, overweight, and obesity) were assessed annually using questionnaires. Maternal educational level was used to indicate SES. Possible explanatory lifestyle determinants (breastfeeding, smoking during pregnancy, smoking during the first three months, and day-care centre attendance) and biological determinants (maternal age at birth, birthweight, and older siblings) were analysed using generalized estimating equations.

RESULTS

This study shows that socio-economic differences in a broad range of health problems are already present early in life, and persist during childhood. Children from families with low socio-economic backgrounds experience more asthma symptoms (odds ratio (OR) 1.27; 95% Confidence Interval (CI) 1.08-1.49), poorer general health (OR 1.36; 95% CI 1.16-1.60), more frequent respiratory infections (OR 1.57; 95% CI 1.35-1.83), more overweight (OR 1.42; 95% CI 1.16-1.73), and more obesity (OR 2.82; 95% CI 1.80-4.41). The most important contributors to the observed childhood socio-economic health disparities are socio-economic differences in maternal age at birth, breastfeeding, and day-care centre attendance.

CONCLUSIONS

Socio-economic health disparities already occur very early in life. Socio-economic disadvantage takes its toll on child health before birth, and continues to do so during childhood. Therefore, action to reduce health disparities needs to start very early in life, and should also address socio-economic differences in maternal age at birth, breastfeeding habits, and day-care centre attendance.

Antenatal steroid therapy for fetal lung maturation and the subsequent risk of childhood asthma: a longitudinal analysis

This study was designed to test the hypothesis that fetal exposure to corticosteroids in the antenatal period is an independent risk factor for the development of asthma in early childhood with little or no effect in later childhood. A population-based cohort study of all pregnant women who resided in Nova Scotia, Canada, and gave birth to a singleton fetus between 1989 and 1998 was undertaken. After a priori specified exclusions, 80,448 infants were available for analysis. Using linked health care utilization records, incident asthma cases developed after 36 months of age were identified. Extended Cox proportional hazards models were used to estimate hazard ratios while controlling for confounders. Exposure to corticosteroids during pregnancy was associated with a risk of asthma in childhood between 3–5 years of age: adjusted hazard ratio of 1.19 (95% confidence interval: 1.03, 1.39), with no association noted after 5 years of age: adjusted hazard ratio for 5–7 years was 1.06 (95% confidence interval: 0.86, 1.30) and for 8 or greater years was 0.74 (95% confidence interval: 0.54, 1.03). Antenatal steroid therapy appears to be an independent risk factor for the development of asthma between 3 and 5 years of age.

Antenatal steroid therapy for fetal lung maturation: is there an association with childhood asthma?

PURPOSE

This study was designed to test the hypothesis that fetal exposure to corticosteroids in the antenatal period is an independent risk factor for the development of asthma in childhood.

METHODS

A population-based cohort study was conducted of all pregnant women who resided in Nova Scotia, Canada, and gave birth to a singleton fetus between January 1989 and December 1998 and lived to discharge. After exclusions, 79,395 infants were available for analysis. Using linked health care utilization records, incident asthma cases between 36 to 72 months of age were identified. Generalized Estimating Equations were used to estimate the odds ratio of the association between exposure to corticosteroids and asthma while controlling for confounders.

RESULTS

Over the 10 years of the study corticosteroid therapy increased by threefold. Exposure to corticosteroids during pregnancy was associated with a risk of asthma in childhood: adjusted odds ratio of 1.23 (95% confidence interval: 1.06, 1.44).

CONCLUSIONS

Antenatal steroid therapy appears to be an independent risk factor for the development of asthma between 36 and 72 months of age. Further research into the smallest possible steroid dose required to achieve the desired post-natal effect is needed to reduce the risk of developing childhood asthma.

Childhood environment and atopic conditions, with emphasis on asthma in a Chilean agricultural area

BACKGROUND

An explanation of the etiology of atopic conditions based on the hygiene hypothesis remains controversial.

OBJECTIVE

To analyze exposure variables in childhood to assess their impact on hay fever, asthma, and sensitization.

METHODS

Data were collected on 1,232 young Chilean adults born between 1974 and 1978. Information was available on consultations for infections early in life, number of siblings, sharing a bedroom, nursery school attendance, and contact with animals in the first 5 years of life. Information on asthma symptoms and rhinitis were obtained from a standardized questionnaire. Sensitization to eight allergens and bronchial hyper responsiveness (BHR) to methacholine were assessed. The study design was non-concurrent longitudinal for infectious episodes and nutritional status in the first year and cross-sectional for the other outcomes.

RESULTS

Number of siblings was associated with sensitization only (p = 0.0048). Nursery school attendance was negatively associated with positive BHR (odds ratio (OR) 0.54, 95% CI 0.30-0.95). A severe respiratory infection early in life was protective of sensitization and wheeze combined (OR 0.29, 95%CI 0.12-0.74). Contact with dogs in the first year was a protective factor of rhinitis (OR 0.47, 95%CI 0.28-0.80), but contact with poultry and cats early in life increased the risk of rhinitis (OR 1.42, 95%CI 1.06-1.88; 1.82, 95%CI 1.06-3.14).

CONCLUSION

The pattern of associations between environmental exposure in early life and atopic conditions was inconsistent. The significant associations were evenly distributed as protective and risk factors of atopic conditions.

Decreased markers of atopy in children with presumed early exposure to allergens, unhygienic conditions, and infections

BACKGROUND

Several risk factors for the development of asthma and atopic disease in children have been described. Furthermore, there is consistent evidence that the prevalence of atopy increases with higher socioeconomic status. The knowledge about risk factors and preventive factors for atopy needs to be improved.

OBJECTIVE

To compare 2 child populations (foster care and reference children) with different risk and protective factors for the development of atopy.

METHODS

The study group consisted of 415 children, living in all 10 community foster homes in Lodz, a large industrial city in Poland. The study was performed from April 2, 2004, to April 30, 2006. The reference group consisted of 500 children, living with their parents at home, recruited from primary care centers. The primary outcome measures were skin prick test results and specific IgE in serum. Secondary outcomes included symptoms of allergic diseases and family history, including life conditions in early childhood.

RESULTS

The full analysis set included 408 study children and 402 reference children. Significant differences were observed in the prevalence of atopy between the study and reference groups (11.3% vs 25.9%). We observed more positive skin prick test results in children from the reference group than in study children. To explain this phenomenon, we selected 16 variables that differ in both groups in early life and relate these to atopy. We found that the more cumulative features characteristic of the foster home population (poor living conditions), the lower the risk of atopy.

CONCLUSION

Extremely unfavorable environmental circumstances, which are characteristic of the foster home population during early childhood, might prevent from atopy.

High prevalence of atopy, but not of asthma, among children in an industrialized area in North Italy: the role of familial and environmental factors--a population-based study

The prevalence of atopy and asthma, and their association with familial and environmental factors were investigated among 13- to 14-yr-old children living in Brescia, an industrialized town in North Italy. All the 1450 children attending primary school in the town were invited to participate, and 967 of them (66.7%, 493 males) provided a valid questionnaire filled in by their parents at home. We used a modified version of the questionnaire adopted in the Italian Study of Respiratory Disorders in Childhood and Environment, which is an extended version of the International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. Six hundred and twenty-eight subjects underwent skin prick test (SPT), and 308 of them (49%) were positive for at least one of the 12 allergen extracts commonly employed. Ninety-nine children (10.2%) had a physician's diagnosis of asthma - 12.4% of the males and 8.0% of the females (p = 0.03). The prevalence of wheezing in the past 12 months was 6.2%. Atopy was found in 76.8% of the subjects with, and in 45.6% of those without physician's diagnosis of asthma (p < 0.001). Analysis by multiple logistic regression showed an inverse association between physician-diagnosed asthma and female sex (odds ratio, OR = 0.5); presence of relatives in the bedroom in initial years of life (OR = 0.6); attending day care (OR = 0.4) and infant school (OR = 0.4); a positive association with parental history of wheezing (OR = 2.5) and asthma (OR = 3.8); and the child's history of asthmatic bronchitis (OR = 31.9) and atopic eczema (OR = 3.8) in the first 2 yr of life. The strength of the associations did not change when restricting the analysis to atopic asthma. In conclusion, atopy and clinical asthma among 13- to 14-yr-old adolescents are significantly associated with some familial and environmental factors, providing further support for the hygiene hypothesis. Prevalence of atopy, but not of asthma, is high in this industrialized area. The strong association found between atopy and clinical asthma suggests that atopy may play a role in causing asthma in genetically predisposed children only.

A nationwide study of indoor and outdoor environments in allergen avoidance and conventional daycare centers in Sweden

Sweden has had specialized 'allergen avoidance daycare centers' (AADC) since 1979. The aim was to compare AADC with ordinary daycare centers (ODC). Through contacts with municipalities and hospitals, 72 AADC were identified. For each AADC, the two nearest ODCs served as controls. A questionnaire was sent to the local directors of the 216 daycare centers (531 sections), 83% responded. A total of 39% of the ODCs had ever had dampness/molds, 12% were near (<500 m) stables/farms, 23% were closer than 50 m to a heavy trafficked road, and 13% were exposed to wood smoke in winter. Only 11% of the AADCs had any child with furred pets at home, while 97% of the ODCs had children with furred pets. Bans on smoking at home and on perfumes were more common at the AADCs (P = 0.001). Fewer AADCs had PVC floors (OR = 0.53; P = 0.01), dampness/molds (OR = 0.55; P = 0.04), shelves (OR 3.03; P = 0.001), curtains (OR = 1.67; P = 0.047), and flowers (OR = 0.03; P < 0.001), while more had daily floor cleaning (OR = 19.9; P = 0.004), weekly wiping of furniture (OR = 11.0; P = 0.001), and washing of pillows/mattresses (OR = 2.74; P = 0.005) and curtains (OR = 9.07; P = 0.001). In conclusion, allergy avoidance daycare centers differ from other daycare centers, and may have better indoor environments.

PRACTICAL IMPLICATIONS

There is a need to improve the indoor environments of daycare centers, including reduction of building dampness and molds. Allergen avoidance daycare centers (AADC) in Sweden differ from ordinary daycare centers in many respects, with fewer indoor and building factors related to dust, allergens and irritants. This shows that the indoor environments of daycare centers can be improved. Data suggest that AADC may have lower levels of pet allergens, and this is beneficial for children with pet allergy. The effects of these improvements on indoor exposures and health of the children need to be further evaluated.

Day-care attendance and increased risk for respiratory and allergic symptoms in preschool age

BACKGROUND

The reported impact of day-care attendance on respiratory and atopic symptoms has varied between studies from different countries. Regarding to the 'hygiene-hypothesis', day-care attendance may lead to less sensitization later in life, but the question still is whether day-care attendance and subsequent exposure to more frequent early infections is a risk or a protection against future allergic disease or asthma (atopic and nonatopic).

METHODS

A cross-sectional postal questionnaire was replied by parents of 10,851 children, aged 1-6 years, in the year 2000 in a Swedish region (DBH-phase 1). The questionnaire focused on respiratory and atopic symptoms, the home environment and information on day care of the children.

RESULTS

Children in day care were reported to have more symptoms than children in home care: adjusted odds ratio (AOR) for wheezing last 12 months, AOR 1.33 (CI 95%: 1.12-1.58), cough at night apart from colds last 12 months AOR 1.56 (CI: 1.17-2.07), doctor diagnosed asthma AOR 1.23 (CI: 0.88-1.71), rhinitis last 12 months AOR 1.15 (CI: 0.92-1.44), doctor diagnosed hay fever AOR 1.75 (CI: 0.94-3.23), eczema last 12 months, AOR 1.49 (CI: 1.24-1.79), allergic reactions to foods, AOR 1.27 (CI: 1.07-1.52), >6 colds last 12 months of 2.57 (CI: 2.12-3.12) and ear infection ever AOR 2.14 (CI: 1.87-2.45). The increased risks were mainly seen and reached significance in the youngest group of children, aged 1-4 years. Adjusting and stratification for the number of airway infections last year did not change the risk associated with day-care attendance for allergic diseases.

CONCLUSIONS

Attending day care was associated with an increased risk of symptoms related to airways infections as well with eczema and allergic reactions to food. No sign of protection from day-care attendance for allergic diseases was found up to 6 years of age. Multiple airway infections and day-care attendance were found to be independently associated with asthma and allergic symptoms.

Asthma and atopy - the price of affluence?

Irrespective of improved knowledge of many aspects of atopic diseases, the unfavorable trends in their prevalence particularly among children could not have been reversed. A growing body of evidence suggests that something may lack from our societal affluence that has the capacity to provide protection against the development of atopic diseases. Much attention during the last years has been devoted to the hygiene hypothesis. This review outlines the impact of environment and lifestyle, particularly from the perspective of the East-West gradient, on the development of atopic diseases, with a special emphasis on the hygiene hypothesis in its broadest sense.

Risk factors for atopic dermatitis in infants at high risk of allergy: the PIAMA study

BACKGROUND

It has been suggested that the period immediately after birth is a sensitive period for the development of atopic disease.

OBJECTIVE

We investigated whether birth characteristics and environmental factors are associated with the development of atopic dermatitis in the first year of life.

METHODS

Seventy-six children with and 228 without atopic dermatitis, all children of mothers with respiratory allergy or asthma (PIAMA birth cohort study) were included in the study. Atopic dermatitis was defined as a positive history of an itchy skin condition with at least two of the following characteristics: visible dermatitis, history of outer arms/leg involvement, or general dry skin. Multiple logistic regression analysis was performed to study the independent effects of various risk factors.

RESULTS

A birth weight >/=4000 g compared to 3000-4000 g was a significant risk factor for atopic dermatitis (odds ratio (OR)=2.4; 95% CI: 1.1-5.1) as was day care attendance (OR=2.9; 95% CI: 1.5-5.9). Exclusive breastfeeding in the first 3 months was negatively associated with atopic dermatitis (OR=0.6; 95% CI: 0.3-1.2), especially with visible dermatitis (OR=0.4; 95% CI: 0.2-1.0). Gender, gestational age, the presence of siblings or pets, and parental smoking were not significantly associated with atopic dermatitis.

CONCLUSION

This study shows that a high birth weight and day care attendance increase the risk of atopic dermatitis in the first year of life, while exclusive breastfeeding is a protective factor when dermatitis is found on inspection.

Familial and environmental determinants for wheezing and asthma in a case-control study of school children in Palestine

BACKGROUND

Our prevalence study on Palestinian school children aged 6-12 years showed lower rates for asthma and asthma symptoms than economically developed and industrialized countries. Reasons for such differences are largely unknown, and could possibly be related to different environmental and lifestyle factors.

OBJECTIVE

To investigate familial, early life exposures and indoor environmental determinants for asthma in children in Palestine.

METHODS

From the population of our previous study, a group of 273 children with wheeze in the past 12 months (of whom 99 children had physician-diagnosed asthma) were matched with an equal number of non-wheezing controls. This case-control study involved a parental questionnaire; skin prick testing (SPT) with mixed house dust mites, cat and dog dander, mixed grass, mixed trees pollen, Alternaria tenuis, olive tree and cockroach extracts; and serum for total and specific IgE for the same eight allergens.

RESULTS

Paternal asthma and maternal hayfever significantly tripled the risk for their children to have wheezing. Previous diagnoses of bronchial allergy, bronchitis, pneumonia, or whooping cough, and positive SPT for house dust mites and cockroaches were significantly more likely among wheezing and asthmatic children than controls. Specific IgE levels for house dust mites and cat allergens showed significantly higher risk for reported wheezing. After adjustment for several environmental and sociodemographic factors using multivariate logistic regression analysis, paternal asthma, maternal hayfever, damp houses, cat and cockroach SPT positivity proved to be strong predictors for wheezing symptoms.

CONCLUSION

Our study confirmed that familial 'atopic' diseases are significant predictors of childhood asthma in Palestinian children. Moreover, indoor environment such as presence of cats and domestic moulds also appear to play a role. Our findings are consistent with studies in Canada, New Zealand, Estonia and Sweden, and show promise to explore further gene-environment interaction in the genesis of asthma.

Asthma: environmental and occupational factors

Asthma is in several ways a difficult disease to study. Generally arising in childhood, its pattern is often one of remission and relapse; at any point there are difficulties in translating its characteristic, clinical features into an operational definition. Geographical and temporal patterns in its distribution - whereby the disease appears to have increased in frequency in more 'westernised' countries -suggest strong environmental determinants in its causation although there are, too, undoubted and important genetic influences on both its incidence and presentation. Recent aetiological research has concentrated on the function of allergen exposure or on the role of early-life microbial contact that may regulate the development of a range of childhood allergies, including asthma. To date the 'hygiene hypothesis' offers the most efficient explanation for the distribution of the disease in time and place although convincing evidence for it remains elusive.