http://repub.eur.nl/res/aut/4136/ List of Publications en http://repub.eur.nl/static-eur/img/logo.png http://repub.eur.nl http://repub.eur.nl/res/pub/28497/ 2010-04-15T00:00:00Z Background. There is ample evidence that childhood overweight is associated with increased risk of chronic disease in adulthood. The aim of this study was to investigate associations between childhood overweight and common childhood health problems. Methods. Data were used from a general population sample of 3960 8-year-old children, participating in the Dutch PIAMA birth cohort study. Weight and height, measured by the investigators, were used to define BMI status (thinness, normal weight, moderate overweight, obesity). BMI status was studied cross-sectionally in relation to the following parental reported outcomes: a general health index, GP visits, school absenteeism due to illness, health-related functional limitations, doctor diagnosed respiratory infections and use of antibiotics. Results. Obesity was significantly associated with a lower general health score, more GP visits, more school absenteeism and more health-related limitations, (adjusted odds ratios around 2.0 for most outcomes). Obesity was also significantly associated with bronchitis (adjusted odds ratio (aOR) and 95% confidence intervals (95%CI): 5.29 (2.58;10.85) and with the use of antibiotics (aOR (95%CI): 1.79 (1.09;2.93)). Associations with flu/serious cold, ear infection and throat infection were positive, but not statistically significant. Moderate overweight was not significantly associated with the health outcomes studied. Conclusion. Childhood obesity is not merely a risk factor for disease in adulthood, but obese children may experience more illness and health related problems already in childhood. The high prevalence of the outcomes studied implies a high burden of disease in terms of absolute numbers of sick children. http://repub.eur.nl/res/pub/17504/ 2009-09-15T00:00:00Z Rationale: Daycare exposes young children to more infections early in life and may thereby prevent the development of asthma and allergy. Objectives: To prospectively study the effect of daycare on the development of asthma and allergic sensitization during the first 8 years of life. Methods: In the Prevention and Incidence of Asthma and Mite Allergy birth cohort 3,963 newborn children were followed prospectively for 8 years. Daycare use and respiratory health were assessed yearly by questionnaires. At 8 years, sensitization to airborne allergens and airway responsiveness were measured. Daycare was defined as early (aged 0-2 yr), late (aged 2-4 yr), or none (no daycare before age 4 yr). Associations of daycare and/or older siblings with asthma symptoms (wheezing, shortness of breath, and inhaled steroids taken in the last year), airway responsiveness, and allergic sensitization were assessed in a longitudinal repeated-event analysis. Measurements and Main Results: Children with early daycare had more wheezing in the first years of life, but less wheezing and steroid use between 4 and 8 years of age. At the age of 8 years, early daycare was not protective for asthma symptoms (adjusted odds ratio [aOR], 0.99; 95% confidence interval [CI], 0.74-1.32), allergic sensitization (aOR 0.86; 95% CI, 0.63-1.18), or airway hyperresponsiveness (aOR, 0.80; 95% CI, 0.57-1.14). The transient reduction in airway symptoms between age 4 and 8 years was only observed in children without older siblings. Conclusion: Early daycare is associated with an increase in airway symptoms until the age of 4 years, and fewer symptoms between the ages of 4 and 8 years. We found no protection against asthma symptoms, hyperresponsiveness, or allergic sensitization at the age of 8 years. http://repub.eur.nl/res/pub/24793/ 2009-08-01T00:00:00Z Background: Recall bias may provide discrepant relationships of pet exposure with sensitization and asthma development. We studied prospectively effects of pets at home on development of sensitization, asthma and respiratory symptoms from birth up to age 8 years. Methods: Event history analysis was performed on annually registered data of 2951 children, participating in the PIAMA birth cohort study. Results: Children with a cat or dog at home at 3 months of age had a significantly lower prevalence of sensitization to inhalant allergens at age 8, but not of asthma. A cat decreased the risk of house dust mite sensitization at age 8 [odds ratio (OR) = 0.68, 95% confidence interval (CI) 0.49-0.95], a dog of pollen sensitization (OR = 0.49, 95% CI: 0.29-0.83). A cat or dog at home did not significantly affect asthma incidence in each subsequent year. From 2 years of age onwards, the incidence of wheeze (OR = 1.52, 95% CI: 1.12-2.05) and a dry cough at night (OR = 1.28, 95% CI: 1.05-1.57) was higher in children with a dog, whereas removal of a dog increased the risk of developing asthma symptoms. Comparing analyses using prospectively and retrospectively collected data on diagnosed asthma showed important recall bias. Conclusions: Our prospective study shows a protective effect of early presence of pets at home on sensitization to inhalant allergens, but no prevention of asthma development. Furthermore, children with pets had more frequent transient or intermittent asthma symptoms. Parental report of asthma by recall may provide spurious results of these associations. http://repub.eur.nl/res/pub/24910/ 2009-07-01T00:00:00Z Background: It is unclear how the association between breast feeding and asthma develops with age of the child and how this association over time is influenced by maternal or paternal allergy. These factors - the age of the child and maternal or paternal allergy - might partly explain the conflicting results observed in cross-sectional studies. Methods: The study population consisted of 3115 Dutch children born in 1996/1997 who participated in the PIAMA (Prevention and Incidence of Asthma and Mite Allergy) birth cohort study. Data on breast feeding and asthma (based on wheeze, dyspnoea and prescription of inhaled steroids) were collected by yearly questionnaires. At 8 years, specific immunoglobulin E (IgE) to airborne allergens and bronchial responsiveness were measured. Data were analysed by logistic regression and generalised estimating equations (GEEs), and stratified by maternal and paternal allergic status. Results: 35% (n=1081) of the children were breast fed for >16 weeks. At 8 years of age, 12.6% (n=392) had asthma. Breast feeding (>16 weeks vs no breast feeding) was significantly associated with a lower asthma prevalence from 3 to 8 years of age, in children of both non-allergic and allergic mothers. The inverse association between breast feeding and sensitisation to airborne allergens at 8 years was non-significant. Breast feeding was not associated with bronchial hyper-responsiveness. No interaction between breast feeding and gender, maternal allergy or paternal allergy was observed in any of the associations. Conclusions: Breast feeding is associated with a lower asthma risk in children until 8 years of age without evidence of attenuation and regardless of the family history of allergy. http://repub.eur.nl/res/pub/16304/ 2009-06-01T00:00:00Z Introduction: ADAM33 is the first identified asthma gene by positional cloning, especially asthma combined with bronchial hyperresponsiveness (BHR). Moreover, ADAM33 is associated with early-life lung function and decline of forced expiratory volume in 1 s (FEV1) in the general population. In utero and postnatal cigarette smoke exposure (CSE) are associated with reduced lung function, and development of BHR and asthma. We hypothesized that this may occur via interaction with ADAM33. Aim: To replicate the role of ADAM33 in childhood lung function and development of BHR and asthma. Furthermore, we investigated gene-environment interaction of ADAM33 with in utero and postnatal CSE in the Dutch PIAMA cohort. Methods: Six ADAM33 single-nucleotide polymorphisms (SNPs) were genotyped. Rint was measured at age 4 and 8 years, FEV1 and BHR at age 8 years; asthma was based on questionnaire data at age 8. Results: In the total cohort, the rs511898 A, rs528557 C, and rs2280090 A alleles increased the risk to develop asthma (+BHR). There existed interaction between in utero but not postnatal CSE and the rs528557 and rs3918396 SNPs with respect to development of BHR, the rs3918396 SNP with Rint at age 8 and the rs528557 SNP with FEV1% predicted. Conclusions: We confirm associations between ADAM33 and the development of asthma (+BHR). This is the first study suggesting that interaction of in utero CSE with ADAM33 results in reduced lung function and the development of BHR, which needs further confirmation. http://repub.eur.nl/res/pub/25401/ 2009-04-01T00:00:00Z OBJECTIVE. Studies among patients have shown accelerated weight gain after (adeno)tonsillectomy.* Whether (adeno)tonsillectomy is also a risk factor for the development of overweight is unknown. We investigated the association between (adeno)tonsillectomy and the subsequent development of overweight in the general population. METHODS. The study population consisted of 3963 children participating in the Dutch Prevention and Incidence of Asthma and Mite Allergy birth cohort. Data on weight and height, adenoidectomy and tonsillectomy, and covariates (gender, birth weight, maternal education, maternal overweight, maternal smoking during pregnancy, breastfeeding, and smoking in the home) were obtained from annual questionnaires completed by the parents. In addition to the questionnaire data, weight and height were measured by the investigators when the children were 8 years old. RESULTS. (Adeno)tonsillectomy between 0 and 7 years of age was significantly associated with overweight and obesity at age 8. Overweight at the age of 2 years was not associated with increased risk of (adeno)tonsillectomy in later years, indicating that the association between (adeno)tonsillectomy and overweight was not explained by preexisting overweight. Longitudinal data on weight and height in the years before and after surgery suggest that (adeno)tonsillectomy forms a turning point between a period of growth faltering and a period of catch-up growth, which might explain the increased risk to develop overweight after the operation. CONCLUSION. Children who undergo (adeno)tonsillectomy are at increased risk to develop overweight in the years after surgery. Copyright http://repub.eur.nl/res/pub/24911/ 2009-02-01T00:00:00Z Background: Caesarean section might be a risk factor for asthma because of delayed microbial colonisation, but the association remains controversial. A study was undertaken to investigate prospectively whether children born by caesarean section are more at risk of having asthma in childhood and sensitisation at the age of 8 years, taking into account the allergic status of the parents. Methods: 2917 children who participated in a birth cohort study were followed for 8 years. The definition of asthma included wheeze, dyspnoea and prescription of inhaled steroids. In a subgroup (n = 1454), serum IgE antibodies for inhalant and food allergens were measured at 8 years. Results: In the total study population, 12.4% (n = 362) of the children had asthma at the age of 8 years. Caesarean section, with a total prevalence of 8.5%, was associated with an increased risk of asthma (OR 1.79; 95% CI 1.27 to 2.51). This association was stronger among predisposed children (with two allergic parents: OR 2.91; 95% CI 1.20 to 7.05; with only one: OR 1.86; 95% CI 1.12 to 3.09) than in children with non-allergic parents (OR 1.36; 95% CI 0.77 to 2.42). The association between caesarean section and sensitisation at the age of 8 years was significant only in children of non-allergic parents (OR 2.14; 95% CI 1.16 to 3.98). Conclusions: Children born by caesarean section have a higher risk of asthma than those born by vaginal delivery, particularly children of allergic parents. Caesarean section increases the risk for sensitisation to common allergens in children with non-allergic parents only. http://repub.eur.nl/res/pub/25459/ 2009-01-01T00:00:00Z The long-chain PUFA (LCPUFA) content of an infant's diet might affect early weight gain. In early trials on supplementation of formula feeding n-3 LCPUFA affected weight gain adversely. n-6 LCPUFA are thought to promote adipose tissue development and might be associated with higher weight gain. We studied the association between the natural n-3 and n-6 LCPUFA content of breast milk of Dutch women and weight and BMI gain of their breast-fed infants in the first year of life. The children in this study were enrolled in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study and were born in 1996-1997 in the Netherlands. Parents reported their child's weight and length in a questionnaire. Of a subgroup of the total population breast-milk samples were collected (n 244). The fatty acid composition of breast milk was determined by GLC and expressed as weight percentages. Linear regression was used for data analysis. Mean gain in weight, length and BMI per week from birth to 1 year of age was 119.5 (sd 16.1) g, 0.48 (sd 0.05) cm and 0.06 (sd 0.03) kg/m2, respectively. The associations between n-6 and n-3 LCPUFA in breast milk, and infant weight, length and BMI gain were weak and inconsistent. The n-3 and n-6 LCPUFA content in breast milk did not affect weight or BMI gain in the first year of life in breast-fed term infants. http://repub.eur.nl/res/pub/14422/ 2008-11-01T00:00:00Z Breastfeeding has been associated with a reduced risk of overweight later in life. This study investigates whether differences in diet and lifestyle at 7 years of age between breastfed and formula-fed children can explain the difference in overweight prevalence at 8 years of age. We studied 2,043 Dutch children born in 1996-1997 who participated in the Prevention and Incidence of Asthma and Mite Allergy birth cohort study. Data on breastfeeding duration and diet and lifestyle factors at 7 years were collected using questionnaires. Weight and height were measured at 8 years. Overweight was defined according to international gender- and age-specific standards. Compared to nonbreastfed children (15.5%, n = 316), children breastfed for >16 weeks (38.0%, n = 776) consumed fruit and vegetables significantly more often and meat, white bread, carbonated soft drinks, chocolate bars, and fried snacks less often. Overall, breastfed children were less likely to have an unhealthy diet (adjusted prevalence ratio: 0.77, 95% confidence interval: 0.61-0.98). The associations could only partly be explained by maternal education, maternal overweight, and smoking during pregnancy. At 8 years, 14.5% (n = 297) of the children were overweight. Breastfeeding for >16 weeks was significantly associated with a lower overweight risk at 8 years (adjusted odds ratio: 0.67, 95% confidence interval: 0.47-0.97), and the association hardly changed after adjustment for diet (adjusted odds ratio: 0.71, 95% confidence interval: 0.49-1.03). Breastfed children had a healthier diet at 7 years compared to nonbreastfed children, but this difference could not explain the lower overweight risk at 8 years in breastfed children. © 2008 The Obesity Society. http://repub.eur.nl/res/pub/15937/ 2008-10-01T00:00:00Z Objective: In young children with asthmatic symptoms diagnostic difficulties lead to use of trials of asthma medication as a diagnostic tool. Our aim is to quantify the persistent use of asthma medication, initiated in the first year of life and identify determinants of this persistent use. Patients and methods: We identified 165 children within the PIAMA (Prevention and Incidence of Asthma and Mite Allergy) birth cohort who used asthma medication before the age of one. Persistent use was investigated during three years after the first prescription. A Cox regression analysis was performed to identify factors associated with persistent use. Results: A total of 58.8% of children continued using asthma medication after the first prescription and 10.3% continued during three years. Children with doctor-diagnosed asthma (Hazard ratio of discontinuation (HR) = 0.64, 95% CI: 0.45-0.91) or prescribed inhaled corticosteroids in the first year of life (HR of discontinuation = 0.59, 95% CI: 0.40-0.86) were 1.6-1.7 times more likely to continue using asthma medication. Conclusions: Persistence of asthma medication, prescribed in the first year of life is very low and is positively associated with doctor-diagnosed asthma and use of inhaled corticosteroids. Characterizing persistent users of asthma medication is important to understand prescribing of asthma medication in this age group. http://repub.eur.nl/res/pub/32502/ 2008-07-15T00:00:00Z Rationale: Maternal diet during pregnancy has the potentialto affect airway development and to promote T-helper-2-cell responses during fetal life. This might increase the riskofdeveloping childhood asthma or allergy. Objectives:We investigated the influence of maternal food consumption during pregnancy on childhood asthma outcomes from 1 to 8 years of age. Methods: A birth cohort study consisting of a baseline of 4,146 pregnant women(1,327 atopic and 2,819nonatopic).These women were asked about their frequency of consumption of fruit, vegeta-bles, fish, egg, milk, milk products, nuts, and nut products during the last month. Their children were followed until 8 years of age. Longitudinal analyses were conducted to assess associations between maternal diet during pregnancy and childhood asthma outcomes over 8 years. Measurements and Main Results: Complete data were obtained for 2,832 children. There were no associations between maternal vegetable, fish, egg, milk or milk products, and nut consumption and longitudinal childhood outcomes. Daily consumptionofnut products increased the risk of childhood wheeze (odds ratio [OR] daily versus rare consumption, 1.42; 95% confidence interval [95% CI], 1.06-1.89), dyspnea (OR, 1.58; 95% CI, 1.16-2.15), steroid use (OR, 1.62; 95% CI, 1.06-2.46), and asthma symptoms (OR, 1.47; 95% CI, 1.08-1.99). Conclusions: Results of this study indicate an increased risk of daily versus rare consumption of nut products during pregnancy on child-hood asthma outcomes.These findings need to be replicated by other studies before dietary advice can be given to pregnant women. http://repub.eur.nl/res/pub/36734/ 2007-08-01T00:00:00Z Background: In adults, body weight tends to be underestimated when based on self-reported data. Whether this discrepancy between measured and reported data exists in healthy young children is unclear. We studied whether parental reported body weight and height of 4-year-old children corresponded with measured body weight and height. In addition, we studied the determinants and the consequences of differences between reported and measured data. Methods: Data on body weight and height of 864 4-year-old Dutch children born in 1996/1997 enrolled in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) birth cohort study were collected via a questionnaire and a medical examination. Overweight was defined according to standard international age and gender specific definitions. Results: Mean differences between measured and reported body weight, height, and body mass index (BMI) were small. Parents of children with a low BMI tended to over report body weight while parents of children with a high BMI tended to underreport body weight. Whereas 9.5% of the children were overweight according to reported BMI, the prevalence of overweight was 13.4% based on measured BMI. Over 45% of the overweight children according to measured BMI were missed when reported BMI was used. Conclusion: These findings suggest that overweight prevalence rates in children are underestimated when based on reported weight and height. http://repub.eur.nl/res/pub/36453/ 2007-06-01T00:00:00Z It has been suggested that early childhood exposure to microbial agents decreases the risk of allergies in children. The current authors studied the association between microbial agents in house dust and allergic sensitisation in children aged 2-4 yrs. Nested case-control studies were performed within ongoing birth cohort studies in Germany, the Netherlands and Sweden and ∼180 sensitised and 180 nonsensitised children were selected per country. Levels of bacterial endotoxin, β(1,3)-glucans and fungal extracellular polysaccharides (EPS) were measured in dust samples from the children's mattresses and the living-room floors. Combined across countries, higher amounts of mattress dust and higher mattress dust loads of endotoxin, β(1,3)-glucans and EPS were associated with a significantly decreased risk of sensitisation to inhalant allergens. After mutual adjustment, only the protective effect of the amount of mattress dust remained significant (odds ratio (95% confidence interval) 0.57(0.39-0.84)). Higher amounts of mattress dust may decrease the risk of allergic sensitisation to inhalant allergens. The effect might be partly attributable to endotoxin, β(1,3)-glucans and extracellular polysaccharides, but could also reflect (additional) protective effects of (microbial) agents other than the ones measured. It is not possible to distinguish with certainty which component relates to the effect, since their levels are highly correlated. Copyright http://repub.eur.nl/res/pub/36645/ 2007-05-15T00:00:00Z Rationale: The relation between birth weight and respiratory symptoms and asthma in children remains unclear. Previous studies focused on a relation at separate ages. A longitudinal analysis may lead to a better understanding. Objectives: To estimate the effect of birth weight on the development and course of respiratory symptoms and asthma in the first 7 years of life. Methods: In a prospective birth cohort study, 3,628 children with a gestational age 37 weeks or more were monitored for 7 years. Parental questionnaires were used to assess respiratory health yearly. Associations of birth weight with respiratory symptoms (wheezing, coughing, respiratory infections) and doctor's diagnosis of asthma were assessed in a repeated-event analysis. Measurements and Main Results: Lower birth weight was associated with more respiratory symptoms (odds ratio [OR] per kg decrease in birth weight, 1.21; 95% confidence interval [CI], 1.09-1.34). The effect of birth weight increased from age 1 to 5, but decreased thereafter and was no longer significant at the age of 7. The effect of birth weight on respiratory symptoms was significantly greater among children exposed to tobacco smoke in their home than among nonexposed children (OR at 5 yr: 1.21 [95% CI, 1.02-1.44] and 1.52 [95% CI, 1.23-1.87], respectively). Birth weight and a doctor's diagnosis of asthma were not related (OR, 1.06; 95% CI, 0.82-1.37). Conclusions: A lower birth weight in children born at term is associated with a transiently increased risk of respiratory symptoms. This effect is enhanced by environmental tobacco smoke exposure. http://repub.eur.nl/res/pub/36471/ 2007-05-01T00:00:00Z Few studies have addressed associations between traffic-related air pollution and respiratory disease in young children. The present authors assessed the development of asthmatic/allergic symptoms and respiratory infections during the first 4 yrs of life in a birth cohort study (n=∼4,000). Outdoor concentrations of traffic-related air pollutants (nitrogen dioxide PM2.5, particles with a 50% cut-off aerodynamic diameter of 2.5 μm and soot) were assigned to birthplace home addresses with a land-use regression model. They were linked by logistic regression to questionnaire data on doctor-diagnosed asthma, bronchitis, influenza and eczema and to self-reported wheeze, dry night-time cough, ear/nose/ throat infections and skin rash. Total and specific immunoglobulin (Ig)E to common allergens were measured in a subgroup (n=713). Adjusted odds ratios (95% confidence intervals) per interquartile pollution range were elevated for wheeze (1.2 (1.0-1.4) for soot), doctor-diagnosed asthma (1.3 (1.0-1.7)), ear/nose/throat infections (1.2 (1.0-1.3)) and flu/serious colds (1.2 (1.0-1.4)). No consistent associations were observed for other end-points. Positive associations between air pollution and specific sensitisation to common food allergens (1.6 (1.2-2.2) for soot), but not total IgE, were found in the subgroup with IgE measurements. Traffic-related pollution was associated with, respiratory infections and some measures of asthma and allergy during the first 4 yrs of life. Copyright http://repub.eur.nl/res/pub/35501/ 2007-04-01T00:00:00Z Compared with nonbreastfed children, breastfed children tend to have a lower body mass index (BMI) at about 1 year of age. How the BMI of breastfed children develops after the first year when this difference in BMI at 1 year of age is considered is not clear. The authors studied the association between breastfeeding and BMI development from 1 to 7 years of age independently of BMI at 1 year of age. Longitudinal BMI data reported by parents of 2,347 Dutch children born in 1996-1997 who participated in the Prevention and Incidence of Asthma and Mite Allergy birth cohort study were collected. Linear regression and mixed-effects models were used for data analyses. Mean BMI at 1 year of age was 17.2 kg/m2(standard deviation, 1.4). Compared with nonbreastfed children, children breastfed for >16 weeks had a lower BMI at 1 year of age, after adjustment for confounders (β = -0.22, 95% confidence interval: -0.39, -0.06). The association between breastfeeding and BMI between 1 and 7 years of age was negligible, while a high BMI at 1 year of age was strongly associated with a high BMI between 1 and 7 years of age in the same model. These findings suggest that the lower BMI and lower risk of overweight among breastfed children later in life are already achieved at 1 year of age. Copyright http://repub.eur.nl/res/pub/8517/ 2002-01-01T00:00:00Z AIMS: To evaluate ethnic differences in the prevalence of respiratory and skin symptoms in the first two years of life. METHODS: A total of 4146 children participated in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study. Parents completed questionnaires on respiratory and skin symptoms, ethnic background, and other potential confounders during pregnancy, and at 3 months, 1 year, and 2 years of age. RESULTS: In the first year, "non-Dutch" children (compared with "Dutch" children) had a higher prevalence of runny nose with itchy/watery eyes (11.0% versus 5.0%). In the second year, a higher prevalence of wheeze at least once (26.7% versus 18.5%), night cough without a cold (24.6% versus 15.5%), runny nose without a cold (34.1% versus 21.3%), and runny nose with itchy/watery eyes (13.7% versus 4.6%) was found. Adjustment for various confounders, especially adjustment for socioeconomic factors, reduced most associations between ethnicity and respiratory symptoms. Only runny nose with itchy/watery eyes in the second year of life was independently associated with non-Dutch ethnicity (adjusted odds ratio 2.89, 95% CI 1.3-6.4). CONCLUSIONS: Non-Dutch children more often had respiratory symptoms in the first two years of life than Dutch children. This could largely be explained by differences in socioeconomic status. Follow up of the cohort will determine whether this higher prevalence of respiratory symptoms in children with non-Dutch ethnicity represents an increased risk of developing allergic disease rather than non-specific or infection related respiratory symptoms. http://repub.eur.nl/res/pub/9766/ 2001-01-01T00:00:00Z OBJECTIVE: To investigate the association between contacts with other children and the development of respiratory infections in the first year of life in children with or without genetic predisposition for allergy. METHODS: Children (n = 4146) who participate in a prospective birth cohort study (Prevention and Incidence of Asthma and Mite Allergy study) were investigated. Questionnaires were used to obtain information on doctor-diagnosed upper respiratory tract infection (URTI) and lower respiratory tract infection (LRTI), child care attendance, having siblings, family history of allergic disease, and various potential confounders. RESULTS: Child care attendance in the first year of life was associated with doctor-diagnosed URTI (adjusted odds ratio [AOR]: 2.7; 95% confidence interval [CI]: 2.1-3.4 for large child care facility vs no child care) and doctor-diagnosed LRTI (AOR: 5.6; 95% CI: 3.9-7.9). Having siblings was associated with doctor-diagnosed LRTI (AOR: 2.6; 95% CI: 2.0-3.4). In addition, children who have allergic parents and attend child care or have older siblings have a higher risk of developing doctor-diagnosed LRTI than do children who have nonallergic parents. CONCLUSIONS: Child care attendance or having siblings increases the risk of developing doctor-diagnosed LRTI in the first year of life to a greater extent in allergy-prone children than in children who are not allergy prone.