Pediatric Asthma Emergency Department Visits Research Articles

Quantifying Multipollutant Health Impacts Using the Environmental Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE): A Case Study in Atlanta, Georgia.

Air pollution risk assessments do not generally quantify health impacts using multipollutant risk estimates, but instead use results from single-pollutant or copollutant models. Multipollutant epidemiological models account for pollutant interactions and joint effects but can be computationally complex and data intensive. Risk estimates from multipollutant studies are therefore challenging to implement in the quantification of health impacts. Our objective was to conduct a case study using a developmental multipollutant version of the Environmental Benefits Mapping and Analysis Program-Community Edition (BenMAP-CE) to estimate the health impact associated with changes in multiple air pollutants using both a single and multipollutant approach. BenMAP-CE was used to estimate the change in the number of pediatric asthma emergency department (ED) visits attributable to simulated changes in air pollution between 2011 and 2025 in Atlanta, Georgia, applying risk estimates from an epidemiological study that examined short-term single-pollutant and multipollutant (with and without first-order interactions) exposures. Analyses examined individual pollutants (i.e., ozone, fine particulate matter, carbon monoxide, nitrogen dioxide (), sulfur dioxide, and particulate matter components) and combinations of these pollutants meant to represent shared properties or predefined sources (i.e., oxidant gases, secondary pollutants, traffic, power plant, and criteria pollutants). Comparisons were made between multipollutant health impact functions (HIF) and the sum of single-pollutant HIFs for the individual pollutants that constitute the respective pollutant groups. Photochemical modeling predicted large decreases in most of the examined pollutant concentrations between 2011 and 2025 based on sector specific (i.e., source-based) estimates of growth and anticipated controls. Estimated number of avoided asthma ED visits attributable to any given multipollutant group were generally higher when using results from models that included interaction terms in comparison with those that did not. We estimated the greatest number of avoided pediatric asthma ED visits for pollutant groups that include (i. e., criteria pollutants, oxidants, and traffic pollutants). In models that accounted for interaction, year-round estimates for pollutant groups that included ranged from 27.1 [95% confidence interval (CI): 1.6, 52.7; traffic pollutants] to 55.4 (95% CI: 41.8, 69.0; oxidants) avoided pediatric asthma ED visits. Year-round results using multipollutant risk estimates with interaction were comparable to the sum of the single-pollutant results corresponding to most multipollutant groups [e.g., 52.9 (95% CI: 43.6, 62.2) for oxidants] but were notably lower than the sum of the single-pollutant results for some pollutant groups [e.g., 77.5 (95% CI: 66.0, 89.0) for traffic pollutants]. Performing a multipollutant health impact assessment is technically feasible but computationally complex. It requires time, resources, and detailed input parameters not commonly reported in air pollution epidemiological studies. Results estimated using the sum of single-pollutant models are comparable to those quantified using a multipollutant model. Although limited to a single study and location, assessing the trade-offs between a multipollutant and single-pollutant approach is warranted. https://doi.org/10.1289/EHP12969.

Neighborhood environmental vulnerability and pediatric asthma morbidity in US metropolitan areas

Research suggests demographic, economic, residential, and health-related factors influence vulnerability to environmental exposures. Greater environmental vulnerability may exacerbate environmentally related health outcomes. We developed a neighborhood environmental vulnerability index (NEVI) to operationalize environmental vulnerability on a neighborhood level. We explored the relationship between NEVI andpediatric asthma emergency department (ED) visits (2014-19) in 3 US metropolitan areas: Los Angeles County,Calif; Fulton County, Ga; and New York City,NY. We performed separate linear regression analyses examining the association between overall NEVI score and domain-specific NEVI scores (demographic, economic, residential, health status) with pediatric asthma ED visits (per 10,000) across each area. Linear regression analyses suggest that higher overall and domain-specific NEVI scores were associated with higher annual pediatric asthma ED visits. Adjusted R2 values suggest that overall NEVI scores explained at least 40% of the variance in pediatric asthma ED visits. Overall NEVI scores explained more of the variance in pediatric asthma ED visits in Fulton County. NEVI scores for the demographic, economic, and health status domains explained more of the variance in pediatric asthma ED visits in each area compared to the NEVI score for the residential domain. Greater neighborhood environmental vulnerability was associated with greater pediatric asthma ED visits in each area. The relationship differed in effect size and variance explained across the areas. Future studies can use NEVI to identify populations in need of greater resources to mitigate the severity of environmentally related outcomes, such as pediatric asthma.

Associations of Air Pollution and Pediatric Asthma in Cleveland, Ohio

Air pollution has been associated with poor health outcomes and continues to be a risk factor for respiratory health in children. While higher particulate matter (PM) levels are associated with increased frequency of symptoms, lower lung function, and increase airway inflammation from asthma, the precise composition of the particles that are more highly associated with poor health outcomes or healthcare utilization are not fully elucidated. PM is measured quantifiably by current air pollution monitoring systems. To better determine sources of PM and speciation of such sources, a particulate matter (PM) source apportionment study, the Cleveland Multiple Air Pollutant Study (CMAPS), was conducted in Cleveland, Ohio, in 2009–2010, which allowed more refined assessment of associations with health outcomes. This article presents an evaluation of short-term (daily) and long-term associations between motor vehicle and industrial air pollution components and pediatric asthma emergency department (ED) visits by evaluating two sets of air quality data with healthcare utilization for pediatric asthma. Exposure estimates were developed using land use regression models for long-term exposures for nitrogen dioxide (NO2) and coarse (i.e., with aerodynamic diameters between 2.5 and 10 μm) particulate matter (PM) and the US EPA Positive Matrix Factorization receptor model for short-term exposures to fine (<2.5 μm) and coarse PM components. Exposure metrics from these two approaches were used in asthma ED visit prevalence and time series analyses to investigate seasonal-averaged short- and long-term impacts of both motor vehicles and industry emissions. Increased pediatric asthma ED visits were found for LUR coarse PM and NO2 estimates, which were primarily contributed by motor vehicles. Consistent, statistically significant associations with pediatric asthma visits were observed, with short-term exposures to components of fine and coarse iron PM associated with steel production. Our study is the first to combine spatial and time series analysis of ED visits for asthma using the same periods and shows that PM related to motor vehicle emissions and iron/steel production are associated with increased pediatric asthma visits.

Hot spots for pediatric asthma emergency department visits in Ottawa, Canada

Objective Pediatric asthma emergency department (ED) visits and repeat visits place a substantial burden on healthcare. National and provincial level studies demonstrate geographic variation in asthma ED visits and links to marginalization, but preclude translation into practical targeting of healthcare delivery. It is important to understand the relationship between pediatric asthma ED visits and marginalization at a more granular level. To map the city-level geographic variation in pediatric asthma ED visit and re-visit rates at the Children’s Hospital of Eastern Ontario (CHEO) in Ottawa, Canada and the relationship with marginalization. Methods We performed a single center retrospective cohort study of children ages 1–17 with one or more ED visits for asthma at the CHEO in Ottawa. Using postal codes, we linked patients to census tracts. Per census tract, we mapped pediatric asthma ED visit and re-visit rates within one year and identified overlap with the Ontario Marginalization Index. Results Of 1,620 children with an index ED visit, 18.5% had a repeat ED visit. We identified 10 hot spot census tracts each for pediatric asthma ED visit and re-visit rates. We identified an overlap between urban hot spots and areas with high ethnic concentration or low dependency. Conclusion At a granular, city-wide level, pediatric asthma ED visit and re-visit rates are heterogeneous. Urban hot spots, in contrast to rural, have more overlap with marginalization, especially ethnic concentration. These methods can be used in other jurisdictions to inform practical community strategies for geographically-targeted prevention of pediatric asthma-related ED visits in vulnerable areas. Abbreviations: ED: Emergency department; CHEO: Children’s Hospital of Eastern Ontario; PRAM: Pediatric Respiratory Assessment Measure; ON-Marg: Ontario Marginalization Index; SES: Socioeconomic status; US: United States Supplemental data for this article can be accessed at publisher’s website.

Associations of short-term exposure to air pollution and emergency department visits for pediatric asthma in Shanghai, China

There is limited evidence regarding the relationship between air pollution and pediatric asthma in developing countries. This study aimed to investigate the association between short-term exposure to ambient air pollutants and pediatric asthma emergency department (ED) visits in Shanghai, China. We collected data on six criteria air pollutants (PM2.5, PM10, NO2, SO2, CO, and O3) and daily ED visits for pediatric asthma patients from 66 hospitals in Shanghai from 2016 to 2018. The generalized additive model combined with polynomial distributed lag model was applied to explore the associations. We fitted two-pollutant models and stratified the analyses by sex, age, and season. In total, we identified 108,817 emergency department visits for pediatric asthma. A 10 μg/m3 increase in the concentrations of PM2.5, NO2, SO2, and O3 was significantly associated with increased risks of pediatric asthma ED visits, with relative risk of pediatric asthma of 1.011 [95% confidence interval (CI): 1.002, 1.021], 1.030 (95%CI: 1.017, 1.043), 1.106 (95%CI: 1.041, 1.174), and 1.009 (95%CI: 1.001, 1.017), respectively. The associations of NO2 remained robust in the two-pollutant models. There were stronger associations for older children (6–18 years) and in warm seasons. The concentration-response curves for pediatric asthma and PM2.5, NO2, SO2, and O3 were steeper at lower and moderate concentrations but became flatter at higher concentrations. This analysis provided evidence that short-term exposure to air pollutants (PM2.5, NO2, SO2, and O3) could increase the risk of asthma exacerbations among children, and health benefits would be gained from improved air quality.

A national burden assessment of estimated pediatric asthma emergency department visits that may be attributed to elevated ozone levels associated with the presence of smoke.

Asthma is the most common pediatric disease in the USA. It has been consistently demonstrated that asthma symptoms are exacerbated by exposure to ozone. Ozone (O3) is a secondary pollutant produced when volatile organic compounds (VOCs) are oxidized in the atmosphere in the presence of nitrogen oxides (NOx). At ground level, elevated ozone is typically formed as a result of human activities. However, wildfires represent an additional source of ozone precursors. Recent evidence suggests that smoke can increase ozone concentrations. We estimated the number of excess asthma-related emergency department (ED) visits in children with asthma that may be attributed to elevated ozone associated with smoke (EOAS) in the USA. We conducted a quantitative burden assessment (BA) using a Monte Carlo approach to estimate the median number of excess pediatric asthma ED visits that may be attributed to EOAS among children with asthma in the continental USA between 2005 and 2014, as well as 95% confidence bounds (95% CB). We estimated that a median of 2403 (95% CB 235-5382) pediatric asthma ED visits could be attributed to EOAS exposure between 2005 and 2014 in the continental USA. Furthermore, the impact of EOAS on estimated asthma ED visits was greatest in the eastern half of the continental USA. We found a significant increase in pediatric asthma ED visits that may be attributed to exposure to EOAS. EOAS may have a measurable negative impact on children with asthma in the USA.

Evaluation of individual and area-level factors as modifiers of the association between warm-season temperature and pediatric asthma morbidity in Atlanta, GA

IntroductionPrevious studies have found associations between respiratory morbidity and high temperatures; however, few studies have explored associations in potentially sensitive sub-populations. MethodsWe evaluated individual and area-level factors as modifiers of the association between warm-season (May-Sept.) temperature and pediatric respiratory morbidity in Atlanta. Emergency department (ED) visit data were obtained for children, 5–18 years old, with primary diagnoses of asthma or respiratory disease (diagnoses of upper respiratory infections, bronchiolitis, pneumonia, chronic obstructive pulmonary disease, asthma, or wheeze) in 20-county Atlanta during 1993–2012. Daily maximum temperature (Tmax) was acquired from the automated surface observing station at Atlanta Hartsfield International Airport. Poisson generalized linear models were used to estimate rate ratios (RR) between daily Tmax and asthma or respiratory disease ED visits, controlling for time and meteorology. Tmax effects were estimated for single-day lags of 0–6 days, for 3-, 5-, and 7-day moving averages and modeled with cubic terms to allow for non-linear relationships. Effect modification by individual factors (sex, race, insurance status) and area-level socioeconomic status (SES; ZIP code levels of poverty, education, and the neighborhood deprivation index) was examined via stratification. ResultsEstimated RRs for Tmax and pediatric asthma ED visits were positive and significant for lag days 1–5, with the strongest single day association observed on lag day 2 (RR=1.06, 95% CI: 1.03, 1.09) for a change in Tmax from 27°C to 32°C (25th to 75th percentile). For the moving average exposure periods, associations increased as moving average periods increased. We observed stronger RRs between Tmax and asthma among males compared to females, non-white children compared to white children, children with private insurance compared to children with Medicaid, and among children living in high compared to low SES areas. Associations between Tmax and respiratory disease ED visits were weak and non-significant (p-value>0.05). ConclusionsResults suggest socio-demographic factors (race/ethnicity, insurance status, and area-level SES) may confer vulnerability to temperature-related pediatric asthma morbidity. Our findings of weaker associations among children with Medicaid compared to other health insurance types and among children living in low compared to high SES areas run counter to our belief that children from disadvantaged households or ZIP codes would be more vulnerable to the respiratory effects of temperature. The potential reasons for these unexpected results are explored in the discussion.

Exploring associations between multipollutant day types and asthma morbidity: epidemiologic applications of self-organizing map ambient air quality classifications

BackgroundRecent interest in the health effects of air pollution focuses on identifying combinations of multiple pollutants that may be associated with adverse health risks.ObjectivePresent a methodology allowing health investigators to explore associations between categories of ambient air quality days (i.e., multipollutant day types) and adverse health.MethodsFirst, we applied a self-organizing map (SOM) to daily air quality data for 10 pollutants collected between January 1999 and December 2008 at a central monitoring location in Atlanta, Georgia to define a collection of multipollutant day types. Next, we conducted an epidemiologic analysis using our categories as a multipollutant metric of ambient air quality and daily counts of emergency department (ED) visits for asthma or wheeze among children aged 5 to 17 as the health endpoint. We estimated rate ratios (RR) for the association of multipollutant day types and pediatric asthma ED visits using a Poisson generalized linear model controlling for long-term, seasonal, and weekday trends and weather.ResultsUsing a low pollution day type as the reference level, we found significant associations of increased asthma morbidity in three of nine categories suggesting adverse effects when combinations of primary (CO, NO2, NOX, EC, and OC) and/or secondary (O3, NH4, SO4) pollutants exhibited elevated concentrations (typically, occurring on dry days with low wind speed). On days with only NO3 elevated (which tended to be relatively cool) and on days when only SO2 was elevated (which likely reflected plume touchdowns from coal combustion point sources), estimated associations were modestly positive but confidence intervals included the null.ConclusionsWe found that ED visits for pediatric asthma in Atlanta were more strongly associated with certain day types defined by multipollutant characteristics than days with low pollution levels; however, findings did not suggest that any specific combinations were more harmful than others. Relative to other health endpoints, asthma exacerbation may be driven more by total ambient pollutant exposure than by composition.Electronic supplementary materialThe online version of this article (doi:10.1186/s12940-015-0041-8) contains supplementary material, which is available to authorized users.

Joint effects of ambient air pollutants on pediatric asthma emergency department visits in Atlanta, 1998-2004.

Because ambient air pollution exposure occurs as mixtures, consideration of joint effects of multiple pollutants may advance our understanding of the health effects of air pollution. We assessed the joint effect of air pollutants on pediatric asthma emergency department visits in Atlanta during 1998-2004. We selected combinations of pollutants that were representative of oxidant gases and secondary, traffic, power plant, and criteria pollutants, constructed using combinations of criteria pollutants and fine particulate matter (PM2.5) components. Joint effects were assessed using multipollutant Poisson generalized linear models controlling for time trends, meteorology, and daily nonasthma upper respiratory emergency department visit counts. Rate ratios (RRs) were calculated for the combined effect of an interquartile range increment in each pollutant's concentration. Increases in all of the selected pollutant combinations were associated with increases in warm-season pediatric asthma emergency department visits (eg, joint-effect RR = 1.13 [95% confidence interval = 1.06-1.21] for criteria pollutants, including ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, and PM2.5). Cold-season joint effects from models without nonlinear effects were generally weaker than warm-season effects. Joint-effect estimates from multipollutant models were often smaller than estimates based on single-pollutant models, due to control for confounding. Compared with models without interactions, joint-effect estimates from models including first-order pollutant interactions were largely similar. There was evidence of nonlinear cold-season effects. Our analyses illustrate how consideration of joint effects can add to our understanding of health effects of multipollutant exposures and also illustrate some of the complexities involved in calculating and interpreting joint effects of multiple pollutants.

State-based Medicaid costs for pediatric asthma emergency department visits.

IntroductionThe prevalence of childhood asthma in the United States increased from 8.7% in 2001 to 9.5% in 2011. This increased prevalence adds to the costs incurred by state Medicaid programs. We provide state-based cost estimates of pediatric asthma emergency department (ED) visits and highlight an opportunity for states to reduce these costs through a recently changed Centers for Medicare and Medicaid Services (CMS) regulation.MethodsWe used a cross-sectional design across multiple data sets to produce state-based cost estimates for asthma-related ED visits among children younger than 18, where Medicaid/CHIP (Children’s Health Insurance Program) was the primary payer.ResultsThere were approximately 629,000 ED visits for pediatric asthma for Medicaid/CHIP enrollees, which cost $272 million in 2010. The average cost per visit was $433. Costs ranged from $282,000 in Alaska to more than $25 million in California.ConclusionsCosts to states for pediatric asthma ED visits vary widely. Effective January 1, 2014, the CMS rule expanded which type of providers can be reimbursed for providing preventive services to Medicaid/CHIP beneficiaries. This rule change, in combination with existing flexibility for states to define practice setting, allows state Medicaid programs to reimburse for asthma interventions that use nontraditional providers (such as community health workers or certified asthma educators) in a nonclinical setting, as long as the service was initially recommended by a physician or other licensed practitioner. The rule change may help states reduce Medicaid costs of asthma treatment and the severity of pediatric asthma.

Emergency Department Crowding and Younger Age Are Associated With Delayed Corticosteroid Administration to Children With Acute Asthma

This study aimed to identify factors associated with delayed or omission of indicated steroids for children seen in the emergency department (ED) for moderate-to-severe asthma exacerbation. This was a retrospective study of pediatric (age ≤ 21 years) patients treated in a general academic ED from January 2006 to September 2011 with a primary diagnosis of asthma (International Classification of Diseases, Ninth Revision code 493.xx) and moderate-to-severe exacerbations. A moderate-to-severe exacerbation was defined as requiring 2 or more (or continuous) bronchodilators. We determined the proportion of visits in which steroids were inappropriately omitted or delayed (>1 hour from arrival). Multivariable logistic regression models were used to identify patient, physician, and system factors associated with delayed or omitted steroids. Of 1333 pediatric asthma ED visits, 817 were for moderate-to-severe exacerbation; 645 (79%) received steroids. Patients younger than 6 years (odds ratio [OR], 2.25; 95% confidence interval [CI], 1.19-4.24), requiring more bronchodilators (OR, 2.82; 95% CI, 2.10-3.79), initially hypoxic (OR, 2.78; 95% CI, 1.33-5.83), or tachypneic (OR, 1.52; 95% CI, 1.05-2.20) were more likely to receive steroids. Median time to steroid administration was 108 minutes (interquartile range, 65-164 minutes). Steroid administration was delayed in 502 visits (78%). Patients with hypoxia (OR, 1.91; 95% CI, 1.11-3.27) or tachypnea (OR, 1.82; 95% CI, 1.17-2.84) were more likely to receive steroids 1 hour or less of arrival, whereas children younger than 2 years (OR, 0.16; 95% CI, 0.07-0.35) and those arriving during periods of higher ED volume (OR, 0.79; 95% CI, 0.67-0.94) were less likely to receive timely steroids. In this ED, steroids were underprescribed and frequently delayed for pediatric ED patients with moderate-to-severe asthma exacerbation. Greater ED volume and younger age are associated with delays. Interventions are needed to expedite steroid administration, improving adherence to National Institutes of Health asthma guidelines.

Joint effects of air pollutants on pediatric asthma emergency department visits

Background: As population exposure to ambient air pollution generally occurs in the form of mixtures, consideration of joint effects of multiple pollutants may advance our understanding of associated health effects. Aims: We assess the joint effect of selected pollutant combinations of interest (groups of oxidant, secondary, traffic, industrial, and 5 criteria pollutants) on warm season pediatric asthma emergency department (ED) visits in Atlanta during 1998-2004. Methods: Daily ambient air pollutant concentrations were obtained from several ambient monitoring networks. We examined associations between ambient air pollutant concentrations and the daily count of pediatric asthma ED visits using multi-pollutant Poisson generalized linear models controlling for time trends, meteorology and the number of non-asthma respiratory ED visits. Joint effects of groups of pollutants were calculated for a simultaneous IQR change in the concentration of each pollutant. Results: Statistically significant joint effects were observed for all of the pollutant groups. Joint effects were overestimated if calculated based on results from single-pollutant models rather than multi-pollutant models. Compared with joint effects estimated from multi-pollutant models without interactions, joint effect estimates from models including first order pollutant interactions were not substantially different for oxidant and secondary pollutants, but were slightly higher for criteria pollutants, traffic pollutants and industrial pollutants. Concurvities were high, but power was adequate to calculate joint effects with ample precision. Conclusions: The vast majority of air pollution health effects studies have focused on single pollutant effects, even if multi-pollutant models have been used. Consideration of joint effects can add to our knowledge of how pollutants act together with respect to health effects, and aligns with the recent emphasis on air pollution mixtures.

Short-term Associations between Ambient Air Pollutants and Pediatric Asthma Emergency Department Visits

Certain outdoor air pollutants cause asthma exacerbations in children. To advance understanding of these relationships, further characterization of the dose-response and pollutant lag effects are needed, as are investigations of pollutant species beyond the commonly measured criteria pollutants. Investigate short-term associations between ambient air pollutant concentrations and emergency department visits for pediatric asthma. Daily counts of emergency department visits for asthma or wheeze among children aged 5 to 17 years were collected from 41 Metropolitan Atlanta hospitals during 1993-2004 (n = 91,386 visits). Ambient concentrations of gaseous pollutants and speciated particulate matter were available from stationary monitors during this time period. Rate ratios for the warm season (May to October) and cold season (November to April) were estimated using Poisson generalized linear models in the framework of a case-crossover analysis. Both ozone and primary pollutants from traffic sources were associated with emergency department visits for asthma or wheeze; evidence for independent effects of ozone and primary pollutants from traffic sources were observed in multipollutant models. These associations tended to be of the highest magnitude for concentrations on the day of the emergency department visit and were present at relatively low ambient concentrations. Even at relatively low ambient concentrations, ozone and primary pollutants from traffic sources independently contributed to the burden of emergency department visits for pediatric asthma.

Acute Associations Between Ambient Air Pollution and Pediatric Asthma Emergency Department Visits in Atlanta, 1993–2004

ISEE-0463 Background and Objective: We investigated effect modification by season and potential confounding by ambient pollen levels and circulating respiratory infections on short-term associations between ambient air pollutants and pediatric emergency department visits for asthma or wheeze. Methods: Hospital-specific daily counts of emergency room visits for asthma or wheeze among children age 5–17 were collected from 41 Metropolitan Atlanta, USA, hospitals during 1993–2004 (n = 91,386 visits). Three-day moving averages of central monitoring station ambient air pollution measurements were calculated for the criteria gases, PM10, coarse PM, PM2.5, and several PM2.5 components. Risk ratios for the warm season (May-October) and cold season (November-April) were estimated via Poisson generalized linear models so as to approximate a case-crossover analysis (matching on year, month, and lag 0 max temperature in Celsius) while accounting for overdispersion. We included a cubic polynomial for day-of-season; indicator variables for hospital and day of week; the daily count of upper respiratory infections among children age 5–17 (aggregated over hospitals); and three-day moving averages of dew point and minimum temperature. We also investigated confounding by ambient levels of several pollen species. Results: We observed several significant positive associations during the warm season and few associations during the cold season. Ozone in particular was strongly associated with pediatric asthma emergency department visits in both seasons. In multipollutant models we observed evidence for effects of both ozone and traffic pollutants. Ambient pollen levels did not appear to confound these relationships. Risk ratio estimates tended to be closer to unity when we controlled for upper respiratory infections, although associations were present regardless. Conclusion: Although we controlled tightly for temperature and temporal trends, we nevertheless observed several positive, statistically significant associations between ambient pollutants and pediatric emergency department visits for asthma and wheeze.

The Relationship of Fall School Opening and Emergency Department Asthma Visits in a Large Metropolitan Area

Asthma morbidity is seasonal, with the fewest exacerbations occurring in summer and the most exacerbations in early fall. To determine if the fall increase in pediatric asthma emergency department (ED) visits is related to the school year start. Time-series study of daily asthma ED visits taken from an administrative claims database for the years 1991 to 2002. Eleven municipal hospitals in New York City, NY. Patients Emergency department visits with asthma as the primary diagnosis among children aged 2 to 4, 5 to 11, and 12 to 17 years and adults with asthma aged 22 to 45 years as comparative group. Main Outcome Measure Rate of asthma ED visits after the September school opening compared with before the opening, during a 60-day window of each year. The delayed effect of school opening was examined by the lagged school-opening indicator for lag 0 through 9 days. The model adjusted for factors that may influence morbidity. There were 86 731 ED visits within the study period. Asthma ED visits for children aged 5 to 11 years were significantly associated with school opening day, with the highest lagged rate ratio being 1.46 (95% confidence interval [CI], 1.29-1.65). For children aged 2 to 4 years, the highest rate ratio was 1.19 (95% CI, 1.06-1.35), and for children aged 12 to 17 years, the highest lagged rate ratio was 1.13 (95% CI, 0.98-1.31). The rise in adult ED visits following school opening was less substantial, with the highest lagged rate ratio being 1.07 (95% CI, 1.00-1.14). The start of the September school year was associated with increases in pediatric asthma ED visits, particularly among grade school children.