Cumulative Incidence Of Asthma Research Articles

The Legacy of Redlining: Increasing Childhood Asthma Disparities Through Neighborhood Poverty.

Identifying the root causes of racial disparities in childhood asthma is critical for health equity. To determine if the 1930's racist policy of redlining led to present-day disparities in childhood asthma by increasing community-level poverty and decreasing neighborhood socioeconomic position (SEP). We categorized census tracts at birth of participants from the Children's Respiratory and Environmental Workgroup birth cohort consortium into A, B, C, or D categories as defined by the Home Owners Loan Corporation (HOLC), with D being the highest perceived risk. Surrogates of present-day neighborhood-level SEP were determined for each tract including the percentage of low-income households, the CDC's social vulnerability index (SVI), and other tract-level variables. We performed causal mediation analysis, which, under the assumption of no unmeasured confounding, estimates the direct and mediated pathways by which redlining may cause asthma disparities through census tract-level mediators adjusting for individual-level covariates. Of 4,849 children, the cumulative incidence of asthma through age 11 was 26.6% and 13.2% resided in census tracts with a HOLC grade of D. In mediation analyses, residing in grade D tracts (aOR = 1.03 [95%CI 1.01,1.05]) was significantly associated with childhood asthma, with 79% of this increased risk mediated by percentage of low-income households; results were similar for SVI and other tract-level variables. The historical structural racist policy of redlining led to present-day asthma disparities in part through decreased neighborhood SEP. Policies aimed at reversing the effects of structural racism should be considered to create more just, equitable, and healthy communities.

Short-term and long-term effects of cesarean section on asthma and wheezing: A cohort study and meta-analysis

ObjectiveTo describe the short-term and long-term effects of cesarean section on childhood asthma and wheezing. MethodFirstly, in the cohort study, 6640 infants were included in the cohort baseline from January 2018 to December 2019, in which 6501 children completed the follow-up study for respiratory diseases at age 2 years. The effect of cesarean section on asthma and wheezing was estimated by the logistic regression model. Secondly, we conducted a meta-analysis of studies with outcomes of childhood asthma and wheezing under 2 years of age and over 2 years of age, respectively, to investigate the short-term and long-term effects of cesarean section on asthma and wheezing. ResultsIn our cohort study, the cumulative incidence of asthma and wheezing was 1.3% (84/6501). 45.5% of children (2961/6501) were born by cesarean section. The adjusted odds ratio for the effect of cesarean section on asthma and wheezing in children under 2 years of age was 1.14 (95%CI 0.73–1.78). Combining previous studies (outcomes of asthma and wheezing under 2 years of age) with our results for a meta-analysis, the odds ratio was 1.15 (95%CI 1.05–1.25, I2 = 46.82%). Meanwhile, cesarean section had a long-term effect on asthma and wheezing in the child population over 2 years of age (OR = 1.17, 95%CI 1.11–1.24, P < 0.001, I2 = 79.38%). ConclusionCesarean section had a short-term effect on asthma and wheezing before the age of 2, in addition, the long-term effect of cesarean section on asthma and wheezing persisted in the child population (under 18).

Atopic heredity modifies the association between maternal vitamin D status in pregnancy and the risk of atopic disease in childhood: an observational study

BackgroundThe relationship between maternal vitamin D status in pregnancy and the development of atopic diseases in the offspring has been frequently studied, but with contradictory results. Previous studies have found an inverse relation between maternal vitamin D in pregnancy and the risk of atopic diseases in the child. In contrast, others have found a higher maternal 25OHD to be related to a higher risk of atopic diseases. Thus, the aim was to investigate the associations between maternal vitamin D status and intake in pregnancy with asthma, eczema and food allergies in the children up to 5 years. In addition, effect modification by reported atopic heredity was studied.MethodsParticipants in the GraviD study had 25-hydroxyvitamin D (25OHD) analyzed in serum in early (T1) and late (T3) pregnancy. Maternal dietary vitamin D intake was estimated from a short food frequency questionnaire and supplement use by questionnaires. At 5 years of age the child´s history of asthma, eczema and food allergy, including atopic heredity, was reported by questionnaire. Multivariable logistic regression was used.ResultsThe cumulative incidence of asthma was 13%, eczema 22%, and food allergy 18%. Only among children without reported atopic heredity, maternal 25OHD of 50–75 nmol/L in T1 was associated with lower odds of asthma (OR 0.271, 95% CI 0.127–0.580), compared to maternal 25OHD > 75 nmol/L. Additionally in these children, maternal 25OHD in T3 (continuous) was associated with asthma (OR 1.014, 95% CI 1.002–1.009), and dietary vitamin D intake with eczema (OR 1.141, 95% CI 1.011–1.288).ConclusionsAmong children without reported atopic heredity, higher maternal vitamin D status and intake during pregnancy was associated with increased risk of reported atopic disease.

A nationwide survey of the association between nonalcoholic fatty liver disease and the incidence of asthma in Korean adults.

BackgroundAsthma and nonalcoholic fatty liver disease (NAFLD) are chronic diseases known to be associated with metabolic abnormalities. We aimed to clarify the association between NAFLD and asthma incidence in a large population-based cohort.Methods and findingsWe selected 160,603 individuals without comorbidities from the National Health Insurance Service-National Sample cohort between 2009 and 2014. NAFLD was defined using a surrogate marker, fatty liver index (FLI). During a median of 5.08 years’ follow-up, 16,377 subjects (10.2%) were newly diagnosed with asthma and categorized into three groups according to FLI. The cumulative incidence of asthma was higher in subjects with higher vs. lower FLIs (FLI < 30, 10.1%; 30 ≤ FLI < 60, 10.8%; FLI ≥ 60, 10.5%). Higher FLI was associated with an increased incidence of asthma (Hazard ratios (HR)highest vs. lowest FLI, 1.25; 95% CI, 1.15–1.36). The results using another definition of NAFLD, as measured by the hepatic steatosis index (HSI), were similar to the primary results. This association was more pronounced in women than in men (HR 1.46; 95% CI, 1.13–1.64 vs. HR 1.07; 95% CI, 0.94–1.20).ConclusionsThis study demonstrated that NAFLD, as measured by FLI and HSI, may influence the incidence rates of asthma in adults, especially in women.

Maternal smoking during pregnancy affects adult onset of asthma in offspring: a follow up from birth to age 46 years.

Environmental tobacco smoke (ETS) exposure increases asthma risk in children. There is limited knowledge of prenatal ETS for adult-onset asthma. To determine the association between prenatal ETS and adult onset asthma. The questionnaire and clinical data of 5200 people, free of physician-diagnosed asthma by 31 years of age, who were included in the Northern Finland Birth Cohort 1966 Study was used. The association of maternal smoking during the last 3 months of pregnancy with onset of physician-diagnosed asthma and with lung function in adult offspring was studied using adjusted multivariate regression analyses. The cumulative incidence of physician-diagnosed asthma between the ages of 31 and 46 years was 5.1% among men and 8.8% among women. Gestational smoke exposure was associated with adult-onset asthma among offspring (adjusted OR 1.54, 95% CI 1.04-2.29), namely among offspring who reported either past non-diagnosed asthma (OR 9.63, 95% CI 2.28-40.67) or past cough with wheeze (3.21, 95% CI 1.71-6.05). A significant association was detected between gestational smoke exposure and the offspring's forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio at 31 years of age. In offspring with the haplotype rs11702779-AA of RUNX1, gestational smoke exposure was associated with adult-onset asthma (5.53, 95% CI 2.11-14.52, adjusted p-value for interaction 0.10). Maternal smoking during pregnancy is associated with the cumulative incidence of asthma in offspring between the ages of 31 and 46 years. The association was accentuated in offspring who at age 31, reported having past respiratory problems and/or who had haplotype rs11702779-AA. A reduction in FEV1/FVC ratio was also observed at age 31 years in offspring with gestational smoke exposure. These results could reflect the early vulnerability of offspring's airways to ETS and its putative long-term effects.

The influence of prenatal mental health service use on the incidence of childhood asthma: a population-based cohort study

ABSTRACTObjectives: We aimed to determine whether maternal mental health service use during pregnancy, a potential proxy measure of prenatal maternal stress, is associated with the development of asthma in a large population-based sample of children. We hypothesized that children born to mothers with mental health service use during pregnancy would have a higher incidence of childhood asthma. Study Design: Health administrative data from Ontario, Canada (population >13 million) was used to identify pairs of mothers linked with their children born between April 1, 2001 to March 31, 2002. Descriptive statistics were used to compare the cumulative incidence of asthma by age 12 years in children whose mothers did or did not have prenatal mental health service use. Multivariable logistic regression was used to estimate the association between prenatal maternal mental health service use and childhood asthma incidence, after adjusting for the child's sex, residency (rural vs. urban), socioeconomic status, comorbid health conditions, low birthweight, and maternal history of asthma. Results: In a population-based sample of 122,333 children, those born to mothers with mental health service use during pregnancy had increased odds of developing asthma (odds ratio: 1.16, 95% confidence intervals: 1.12, 1.20, p < 0.001). Conclusions: Prenatal maternal mental health service use is an independent risk factor for the development of asthma in childhood. This supports growing evidence for the importance of in utero exposure to maternal stress factors in asthma pathogenesis. This study highlights a potential strategy for the primary prevention of childhood asthma, namely improved recognition and management of mental health issues and stress in pregnant mothers.

Early Probiotic Supplementation for Eczema and Asthma Prevention: A Randomized Controlled Trial.

To determine if probiotic administration during the first 6 months of life decreases childhood asthma and eczema. We conducted a randomized, double-blind controlled trial of Lactobacillus rhamnosus GG (LGG) supplementation on the cumulative incidence of eczema (primary end point) and asthma and rhinitis (secondary end points) in high-risk infants. For the first 6 months of life, intervention infants (n = 92) received a daily dose of 10 billion colony-forming units of LGG and 225 mg of inulin (Amerifit Brands, Cromwell, CT), and control infants (n = 92) received 325 mg of inulin alone. We used survival analysis methods to estimate disease incidences in the presence or absence of LGG and to estimate the efficacy of LGG in delaying or preventing these diseases. Infants were accrued over a 6-year period (median follow-up: 4.6 years; 95% retention rate at 2 years). At 2 years of age, the estimated cumulative incidence of eczema was 30.9% (95% confidence interval [CI], 21.4%-40.4%) in the control arm and 28.7% (95% CI, 19.4%-38.0%) in the LGG arm, for a hazard ratio of 0.95 (95% CI, 0.59-1.53) (log-rank P = .83). At 5 years of age, the cumulative incidence of asthma was 17.4% (95% CI, 7.6%-27.1%) in the control arm and 9.7% (95% CI, 2.7%-16.6%) in the LGG arm, for a hazard ratio of 0.88 (95% CI, 0.41-1.87) (log-rank P = .25). For high-risk infants, early LGG supplementation for the first 6 months of life does not appear to prevent the development of eczema or asthma at 2 years of age.

Association of living in a farming environment with asthma incidence in Canadian children

ABSTRACTObjective: The objective of this population-based 14-year follow-up study was to examine the effect of living in a farm environment on asthma incidence in children. Methods: A total of 10,941 children of ages 0 to 11 years who were free of asthma and wheeze at the baseline (1994–1995) in the National Longitudinal Survey of Children and Youth were considered in the study. Children's living environment was classified, based on interviewer's observation, into three categories: non-rural, rural non-farming, and farming. An incidence of asthma was obtained from health-professional diagnosed asthma reported either by the person most knowledgeable for children under 15 years or by the children themselves if they were of ages 16 years and over. Results: The 14-year cumulative incidence of asthma among children living in farming environments was 10.18%, which was significantly lower than that observed for children living in rural non-farming (13.12%) and non-rural environments (16.50%). After adjusting for age group, number of older siblings, allergy, parental history of asthma, dwelling in need of repairs and SES index, a dose-response relationship was observed with children living in rural non-farming and farming environments having significantly reduced risk of asthma [hazard ratio (HR): 0.77; 95% confidence interval (CI): (0.60, 1.00); p = 0.047 and HR: 0.56; 95% CI: (0.41,0.77); p < 0.001] in comparison to those living in non-rural environments. Conclusion: This cohort study provides further evidence that living in a farming environment during childhood is protective of asthma incidence in adolescence and adulthood and this finding provides further support for the hygiene hypothesis.

Smoking and New-Onset Asthma in a Prospective Study on Italian Adults

Background: The existence of a cause-effect relation between active smoking and new-onset asthma in adults, although supported by several studies, has not been proven yet. Aims: We aimed to prospectively study asthma incidence as a function of smoking habits in the Italian adult population. Methods: A population-based cohort of 5,241 non-asthmatics was enrolled in Verona and Sassari in 1998-2000. The cohort was contacted again in 2007-2009 within the Gene-Environment Interactions in Respiratory Diseases study, and 3,187 subjects (60.8%) answered a screening questionnaire on smoking habits and respiratory disorders. The relation between smoking habits and self-reported new-onset asthma, defined as asthma attacks/use of medicines for asthma, was investigated by a multivariable logistic model. Results: During follow-up, 145 new cases of asthma were observed, yielding a cumulative incidence of 4.6% (95% CI 3.9-5.4); cumulative incidence of asthma did not significantly differ among never-smokers (76/1,666 = 4.6%), ex-smokers (30/554 = 5.4%) and current smokers (39/883 = 4.4%) (p = 0.641). In a multivariable analysis, the most important risk factor for asthma onset was allergic rhinitis (OR = 4.00, 95% CI 3.68-4.35). Compared to never-smokers, the risk of asthma onset was slightly increased in ex-smokers (OR = 1.28, 1.09-1.49) but not in current smokers (OR 1.01, 0.66-1.53). Current smoking became a significant predictor only when both new-onset wheezing and new-onset asthma were considered as the outcome (OR = 2.03, 1.35-3.05). Conclusions: In this prospective study, current smoking was not a risk factor for new-onset asthma, unless new-onset wheezing was also considered. The increase in asthma incidence among ex-smokers was likely due to reverse causation.

Metabolic syndrome and incidence of asthma in adults: the HUNT study

Obesity is a risk factor for incident asthma in adults, and obesity is a major component of metabolic syndrome. This study aimed to explore the associations of metabolic syndrome and its components with the cumulative incidence of asthma in adults. We conducted a prospective cohort study of participants who were asthma-free at baseline (n = 23 191) in the Nord-Trøndelag Health Study from 1995 to 2008. Baseline metabolic syndrome was categorised using the definition of the Joint Interim Statement from several international organisations. Incident asthma was self-reported at follow-up, which averaged 11 years. Metabolic syndrome was a risk factor for incident asthma (adjusted OR 1.57, 95% CI 1.31-1.87). This association was consistent in sensitivity analyses using a stricter asthma definition (adjusted OR 1.42, 95% CI 1.13-1.79). Among the components of metabolic syndrome, two remained associated with incident asthma after mutual adjustment for the other metabolic components: high waist circumference (adjusted OR 1.62, 95% CI 1.36-1.94) and elevated glucose or diabetes (adjusted OR 1.43, 95% CI 1.01-2.04). Metabolic syndrome and two of its components (high waist circumference and elevated glucose or diabetes) were associated with an increased risk of incident asthma in adults.

Maternal dietary fat and fatty acid intake during lactation and the risk of asthma in the offspring

To explore the association between maternal dietary fat and fatty acid (FA) intake during lactation, and the risk of asthma in the offspring by the age of 5 years. The subjects comprised 1798 mother-child pairs from the Type 1 Diabetes Prediction and Prevention (DIPP) Nutrition Study. Dietary intake was assessed by a validated 181-item food frequency questionnaire, which covered the third month of lactation. The cumulative incidence of asthma was assessed at the age of 5 years with a questionnaire modified from the International Study of Asthma and Allergies in Childhood (ISAAC). Cox proportional hazards regression was used for statistical analysis. The maternal use of margarines during lactation was associated with a marginally increased risk of asthma [hazard ratio (HR) for user vs. nonuser 1.96, 95% confidence interval (CI) 1.01-3.82, p = 0.047] after adjusting for putative confounders. The maternal intakes of n-3 polyunsaturated FA (PUFA) and fish during lactation were not associated with the risk of asthma. Maternal use of margarines during lactation was weakly associated with an increased risk of asthma in the offspring at the age of 5 years. Other fats or FAs during lactation were not associated with the risk of asthma. However, the nonadherence to dietary recommendations regarding especially fats of our study population may restrict the generalizability of our results.

The Risk of Asthma in Late Preterm Infants

RationalePreterm infants have been reported to have a higher risk of asthma compared to term infants. However, little is known about the risk of asthma among late preterm (LPT) infants (34 0/7 to 36 6/7 weeks of gestation).MethodsThis study used a retrospective birth cohort born in Olmsted County, Minnesota from 2002 through 2006 that was identified using the Rochester Epidemiology Project. Appropriate for gestational age (AGA) weight LPT infants and AGA term infants (37 0/7 to 40 6/7 weeks of gestation) were randomly sampled with regard to gender, birth year, and institution using frequency matching. Asthma status was ascertained by applying predetermined criteria for asthma. Study subjects were followed until 12/31/2010 by censoring event, last follow up date, and end of study period. Cumulative incidence of asthma during the first 8 years of life was compared using log-rank test and Kaplan-Meier curves.ResultsThere were 654 LPT infants and 7447 term infants born during the study period. We enrolled 200 eligible AGA LPT infants and 200 frequency matched term infants. In this preliminary report, 119 LPT infants (50% male, 67% Caucasian) and 116 term infants (54% male, 72% Caucasian) were available. The cumulative incidence of asthma among LPT infants during the study period was 24.5% while in term infants it was 14.5% (p=0.041).ConclusionsBased on this preliminary data, the risk of asthma is higher in former LPT infants. The results warrant completion of this ongoing study given the significant finding. The nature of this association needs to be further examined. RationalePreterm infants have been reported to have a higher risk of asthma compared to term infants. However, little is known about the risk of asthma among late preterm (LPT) infants (34 0/7 to 36 6/7 weeks of gestation). Preterm infants have been reported to have a higher risk of asthma compared to term infants. However, little is known about the risk of asthma among late preterm (LPT) infants (34 0/7 to 36 6/7 weeks of gestation). MethodsThis study used a retrospective birth cohort born in Olmsted County, Minnesota from 2002 through 2006 that was identified using the Rochester Epidemiology Project. Appropriate for gestational age (AGA) weight LPT infants and AGA term infants (37 0/7 to 40 6/7 weeks of gestation) were randomly sampled with regard to gender, birth year, and institution using frequency matching. Asthma status was ascertained by applying predetermined criteria for asthma. Study subjects were followed until 12/31/2010 by censoring event, last follow up date, and end of study period. Cumulative incidence of asthma during the first 8 years of life was compared using log-rank test and Kaplan-Meier curves. This study used a retrospective birth cohort born in Olmsted County, Minnesota from 2002 through 2006 that was identified using the Rochester Epidemiology Project. Appropriate for gestational age (AGA) weight LPT infants and AGA term infants (37 0/7 to 40 6/7 weeks of gestation) were randomly sampled with regard to gender, birth year, and institution using frequency matching. Asthma status was ascertained by applying predetermined criteria for asthma. Study subjects were followed until 12/31/2010 by censoring event, last follow up date, and end of study period. Cumulative incidence of asthma during the first 8 years of life was compared using log-rank test and Kaplan-Meier curves. ResultsThere were 654 LPT infants and 7447 term infants born during the study period. We enrolled 200 eligible AGA LPT infants and 200 frequency matched term infants. In this preliminary report, 119 LPT infants (50% male, 67% Caucasian) and 116 term infants (54% male, 72% Caucasian) were available. The cumulative incidence of asthma among LPT infants during the study period was 24.5% while in term infants it was 14.5% (p=0.041). There were 654 LPT infants and 7447 term infants born during the study period. We enrolled 200 eligible AGA LPT infants and 200 frequency matched term infants. In this preliminary report, 119 LPT infants (50% male, 67% Caucasian) and 116 term infants (54% male, 72% Caucasian) were available. The cumulative incidence of asthma among LPT infants during the study period was 24.5% while in term infants it was 14.5% (p=0.041). ConclusionsBased on this preliminary data, the risk of asthma is higher in former LPT infants. The results warrant completion of this ongoing study given the significant finding. The nature of this association needs to be further examined. Based on this preliminary data, the risk of asthma is higher in former LPT infants. The results warrant completion of this ongoing study given the significant finding. The nature of this association needs to be further examined.

Persistence of multiple illnesses in World Trade Center rescue and recovery workers: a cohort study

More than 50,000 people participated in the rescue and recovery work that followed the Sept 11, 2001 (9/11) attacks on the World Trade Center (WTC). Multiple health problems in these workers were reported in the early years after the disaster. We report incidence and prevalence rates of physical and mental health disorders during the 9 years since the attacks, examine their associations with occupational exposures, and quantify physical and mental health comorbidities. In this longitudinal study of a large cohort of WTC rescue and recovery workers, we gathered data from 27,449 participants in the WTC Screening, Monitoring, and Treatment Program. The study population included police officers, firefighters, construction workers, and municipal workers. We used the Kaplan-Meier procedure to estimate cumulative and annual incidence of physical disorders (asthma, sinusitis, and gastro-oesophageal reflux disease), mental health disorders (depression, post-traumatic stress disorder [PTSD], and panic disorder), and spirometric abnormalities. Incidence rates were assessed also by level of exposure (days worked at the WTC site and exposure to the dust cloud). 9-year cumulative incidence of asthma was 27·6% (number at risk: 7027), sinusitis 42·3% (5870), and gastro-oesophageal reflux disease 39·3% (5650). In police officers, cumulative incidence of depression was 7·0% (number at risk: 3648), PTSD 9·3% (3761), and panic disorder 8·4% (3780). In other rescue and recovery workers, cumulative incidence of depression was 27·5% (number at risk: 4200), PTSD 31·9% (4342), and panic disorder 21·2% (4953). 9-year cumulative incidence for spirometric abnormalities was 41·8% (number at risk: 5769); three-quarters of these abnormalities were low forced vital capacity. Incidence of most disorders was highest in workers with greatest WTC exposure. Extensive comorbidity was reported within and between physical and mental health disorders. 9 years after the 9/11 WTC attacks, rescue and recovery workers continue to have a substantial burden of physical and mental health problems. These findings emphasise the need for continued monitoring and treatment of the WTC rescue and recovery population. Centers for Disease Control and Prevention and National Institute for Occupational Safety and Health.

Allergic rhinoconjunctivitis doubles the risk for incident asthma – Results from a population study in Helsinki, Finland

To examine the incidence of allergic rhinoconjunctivitis and asthma, and to assess allergic rhinoconjunctivitis as a risk factor for incident asthma, we performed a 11-year follow-up postal survey. The original study population was a random population sample of 8000 inhabitants of Helsinki aged 20-69 years in 1996. Participants in the first postal questionnaire survey, 6062 subjects, were invited to this follow-up study, and provided 4302 (78%) answers out of 5484 traced subjects in 2007. Cumulative incidence of asthma from 1996 to 2007 was 4.0% corresponding to an annual incidence rate of 3.7/1000/year. After exclusion of those with asthma medication or physician-diagnosed chronic bronchitis or COPD at baseline in 1996, the cumulative incidence decreased to 3.5% (incidence rate 3.2/1000/year), and further to 2.7% (2.5/1000/year) when also those reporting recurrent wheeze or shortness of breath during the last year in 1996 were omitted from the population at risk. Remission of asthma occurred in 43 subjects and was 16.9% over 11 years. Cumulative 11-year incidence of allergic rhinoconjunctivitis was 16.9% corresponding to 16.8/1000/year, and cumulative remission was 18.1%. Incidence of allergic rhinoconjunctivitis was significantly lower among those who had lived in the countryside or on a farm during the first 5 years of life, but this was not true for asthma. In multivariate analysis, farm living during the first 5 years of life was protective for the development of allergic rhinoconjunctivitis, OR 0.75 (95%CI 0.57-0.99). Allergic rhinoconjunctivitis was a significant independent risk factor for incident asthma, OR 2.15 (95%CI 1.54-3.02). In the cohort, the prevalence of rhinoconjunctivitis increased from 38.0% in 1996 to 40.9% in 2007, physician-diagnosed asthma from 6.8% to 9.4%, while current smoking decreased from 31.3% to 23.3%. Incidence of allergic rhinoconjunctivitis was higher than in earlier studies, while asthma incidence remained on similar level, both being significantly higher in women. Allergic rhinoconjunctivitis doubled the risk for incident asthma.

PVC - as flooring material - and its association with incident asthma in a Swedish child cohort study

The Dampness in Buildings and Health study (DBH) started in the year 2000 in Värmland, Sweden, with a baseline questionnaire sent to all children (n = 14,077) aged 1-6. Five years later, a follow-up questionnaire was sent to the children who were 1-3 years at baseline. A total of 4779 children participated in both the baseline and the follow-up studies and constitute the study population in this cohort study. The aim of this study was to examine the association between exposure to PVC-flooring in the child's and parent's bedroom in homes of children aged 1-3 and the incidence of asthma, rhinitis, and eczema during the following 5-year period. Adjusted analyses showed that the incidence of asthma among children was associated with PVC-flooring in the child's bedroom (AOR 1.52; 95% CI 0.99-2.35) and in the parent's bedroom (1.46; 0.96-2.23). The found risks were on borderline of significance and should therefore be interpreted with caution. There was further a positive relationship between the number of rooms with PVC-flooring and the cumulative incidence of asthma. PVC-flooring was found to be a stronger risk factor for incident asthma in multifamily homes when compared with single-family houses and in smoking families compared with non-smoking families and in women. These longitudinal data from the DBH study found an association between the presence of PVC-flooring in the home and incident asthma in children. However, earlier results from the DBH study have shown that PVC-flooring is one important source for phthalates in indoor dust, and exposure to such phthalates was found to be associated with asthma and allergy among children. This emphasizes the need for prospective studies that focus on the importance of prenatal and neonatal exposure to phthalates in the development of asthma and allergy in children.

Vehicle exhaust outside the home and onset of asthma among adults

Few studies have investigated the relationship between vehicle exhaust and the new onset of asthma among adults. The aim of the present prospective cohort study was to investigate the relationship between the cumulative incidence of asthma and onset of asthma among adults and vehicle exhaust concentrations at home. Participants from three Swedish cities included in the Respiratory Health in Northern Europe cohort constituted the study population. Exposure at each participant's home was calculated using dispersion models. We also used <50 m distance to nearest major road as a more simple indicator of exposure. The adjusted model included 3,609 participants, of which 107 were classified as onset cases and 55 as true incident cases of asthma. There was a positive association between asthma onset (odds ratio (OR) per 10 microg x m(-3) 1.46, 95% confidence interval (CI) 1.07-1.99) and incident asthma (OR per 10 microg x m(-3) 1.54, 95% CI 1.00-2.36) and the levels of nitrogen dioxide (NO(2)), which remained statistically significant after adjusting for potential confounders. The relationship between asthma and NO(2) was not significantly modified by sex, hay fever or wheeze. The risk of developing asthma was also significantly related to living close to a major road. The current study suggests that elevated levels of vehicle exhaust outside the home increase the risk of onset and incident asthma among adults.

Cesarean Section and Risk of Severe Childhood Asthma: A Population-Based Cohort Study

To explore the possible association between delivery by cesarean section (CS) and later development of asthma. A population-based cohort study of 1,756,700 singletons reported to the Medical Birth Registry of Norway between 1967 and 1998, followed up to age 18 years or the year 2002. Exposure was the mode of delivery (spontaneous vaginal, instrumental vaginal, or CS, with planned and emergency CS separately from 1988 onward). Outcome was asthma registered in the National Insurance Scheme, which provides cash benefits to families of children with severe chronic illnesses. We used multivariate Cox proportional hazard models to examine associations between exposure and outcome. The cumulative incidence of asthma was 4.0/1000. Children delivered by CS had a 52% increased risk of asthma compared with spontaneously vaginally delivered children (adjusted hazard ratio [HR] = 1.52; 95% confidence interval [CI] = 1.42 to 1.62). Between 1988 and 1998, planned and emergency CS was associated with a 42% (HR = 1.42; 95% CI = 1.25 to 1.61) and 59% (HR = 1.59; 95% CI = 1.44 to 1.75) increased risk of asthma, respectively. We found a moderately increased risk of asthma in the children delivered by CS. The possibly stronger association with emergency CS compared with planned CS could be worth pursuing to investigate possible causal mechanisms.

Incidencia de asma y factores de riesgo en una cohorte de escolares desde los 6-7 años hasta los 14-15 años en Castellón, según el Estudio Internacional de Asma y Alergias en la Infancia (ISAAC)

To estimate the incidence of asthma in schoolchildren from 6-7 years old to 14-15 years old and associated risk factors. A cohort study, with the ISAAC phases I and III in 1994 and 2002, respectively, was carried out in Castellón, and the nearby towns Vila-real, Almassora, Benicàssim, El Grau de Castelló, Borriol, and L'Alcora. In 1992, 3,607 schoolchildren aged 6-7 years old took part, of whom 1,805 were again studied in 2002, at the age of 14-15. New cases of asthma were defined following the ISAAC questionnaire. Poisson regression was used in the analysis of asthma risk factors. Participation was 50.0%. The cumulative incidence of asthma was 6.4% during the 8 years of study, 108 new cases of 1,698 schoolchildren free of asthma at beginning. Incidence was greater in boys than girls, and in 14-year old teenagers compared to 15-year olds, although differences were not significant. Risk factors associated with the incidence of asthma were: family history of asthma, history of allergic rhinitis, history of bronchitis and upper-middle compared to lower social class. A low incidence of asthma was found in schoolchildren from Castellón, Spain, in comparison with other cohort studies. Estimated risk factors were generally in accordance with incidence studies.

Childhood asthma and human leukocyte antigen type

Little is known about the relationship between human leukocyte antigen (HLA) class II genes and family history of asthma or atopy in relation to the incidence of childhood asthma. The objective of the study was to determine whether specific HLA class II genes (e.g., DRB1*03) are associated with asthma and whether such association explains the influences of family history of asthma or atopy on asthma incidence. A stratified random sample of 340 children who had HLA data available from the Rochester Family Measles Study cohort (n= 876) and a convenience sample of healthy children aged 5-12 years were the participants. We conducted comprehensive medical record reviews to determine asthma status of these children. The associations between the presence of specific HLA alleles and development of asthma and the role of family history of asthma or atopy in the association were evaluated by fitting Cox models. The cumulative incidence of asthma by 12 years of age among children who carry HLA DRB1*03 was 33%, compared to 24.2% among those who did not carry this allele. Adjusting for family history of asthma or atopy, gender, low birth weight, season of birth, HLA DRB1*04, and HLA DQB1*0302, the hazards ratio for HLA DRB1*03 carriers was 1.8 (95% confidence interval: 1.1-2.9, P= 0.020). We concluded that the HLA DRB1*03 allele is associated with asthma. However, the HLA class II gene does not explain the influences of family history of asthma or atopy on development of asthma. The mechanism underlying the association between asthma and HLA genes needs to be elucidated.

A comparative study of asthma, pollen, cat and dog allergy among pupils and allergen levels in schools in Taiyuan city, China, and Uppsala, Sweden

We compared the school environment, asthma and allergy in 10 schools in Taiyuan, China, with eight schools in Uppsala, Sweden. In total 2193 pupils (mean age 13 years) participated. Chinese pupils had more respiratory symptoms, particularly daytime breathlessness after exercise (29.8% vs. 7.1%; P < 0.001), while cat allergy (1.2% vs. 6.6%; P < 0.001) and dog allergy (1.3% vs. 4.0%; P < 0.01) was less common. Cumulative incidence of asthma (1.8% vs. 9.5%; P < 0.001) and doctor's diagnosed asthma (1.2% vs. 9.0%; P < 0.001) were less common in China, indicating an under-diagnosis of asthma. Chinese classrooms were colder (mean 14.7 vs. 21.4 degrees C), more humid (mean 42% vs. 31% RH) and had higher CO2-levels (mean 2211 vs. 761 ppm). Levels of cat (Fel d1), dog (Can f1) allergens were low in settled dust from China (< 200 ng/g dust), but high in airborne dust on Petri-dishes (GM 16.8 ng/m2/day for Fel d1 and 17.7 for Can f1). The Swedish settled dust contained cat, dog and horse allergens in high levels (median 1300 ng/g, 1650 ng/g, 1250 U/g dust, respectively). In conclusion, there were large differences in the school environment, and in respiratory symptom and allergy. Allergen measurements in settled dust only may largely underestimate the classroom exposure. Practical Implications There is a need to improve the school environment, both in China and Sweden. The Swedish schools contained high levels of cat, dog and horse allergens and more amounts of open shelves and textiles that can accumulate dust and allergens. The air measurements indicated that Chinese schools may contain significant amounts of cat and dog allergen, and analysis of settled dust only may not reflect the true allergen exposure. Since the Chinese schools had no mechanical ventilation, they could not fulfill the ventilation standard in winter, and hence there is a need for improving the ventilation. The great discrepancy between respiratory symptoms and reports on asthma, and the high prevalence of attacks of breathlessness without wheeze, may have implication for future questionnaire studies on asthma in China.