Data were collected as part of a cross-sectional study of asthma prevalence during the 2002-2003 school year.23
The project was reviewed and approved by the Mount Sinai Institutional Review Board, the Mount Sinai Health Insurance Portability and Accountability Act Office and the New York City Department of Education's Division of Assessment and Accountability.
Methodology for this study has been reported in previous publications.23,24
Briefly, New York City ZIP Codes were ranked and grouped according to their childhood asthma hospitalization rate. To obtain a representative sample of New York City school children, the ZIP Codes within the three groups with the highest, median, and lowest asthma hospitalization rates were eligible for inclusion in the study. One public elementary school per eligible ZIP Code was randomly selected with probability proportional to size. A total of 26 schools were selected, 8 within each strata and two additional schools in the area of low asthma hospitalization to compensate for the lower expected prevalence. To control for seasonality of asthma symptoms, which could affect reported medication use, schools from each of the three groups were assessed concurrently during overlapping 2-week periods, and so equal numbers of schools were assessed during the fall, winter, and spring seasons.
Within each school, questionnaires were distributed in two randomly selected classrooms per grade level, kindergarten through 5th
grade, and up to two self-contained special education classrooms where available. As described in a previous publication24
, an interactive presentation was given in each classroom, and children were instructed to bring the questionnaire home to their parent/guardian and return the completed form within two weeks. Both children and teachers were given nominal incentives, such as school supplies, to encourage participation.
The parental questionnaire was adapted from a previous study of childhood asthma and was available in English, Spanish, or Chinese.25
To ensure clarity and cultural appropriateness, the questionnaire was pilot-tested among groups of native speakers, prior to the study. The questionnaire contained standardized items on demographics, household environment, asthma diagnosis and symptoms, medication use and healthcare utilization. Ever having asthma was defined as a positive response to the following question, “Have you or your child ever been told by a doctor or nurse that he/she has asthma?”. Children who also reported wheezing in the previous 12 months were identified as having current asthma.
Because the NHLBI guidelines recommend long-term control medication for all children with persistent asthma2
, we sought to examine a subset of children who would fall into this category based on their reported symptoms. The NHLBI classification scheme uses a combination of day and nighttime symptoms, medication use, and lung function tests in order to categorize asthma severity in a clinical setting.2
In this study, we used sleep disturbances due to asthma as the marker for asthma severity. In order to be consistent with the NHLBI classification scheme, children with a physician's diagnosis of asthma who also reported one or more sleep disturbances due to asthma per week were designated “persistent”, requiring treatment with long-term controller medication.
Use of medications, was ascertained by including a table of commonly prescribed medications on the questionnaire and allowing respondents to indicate which medications their children used during the past 2 weeks, as well as frequency of use. There was also an area where parents could include medications not listed. For the purpose of this study, long-term control medications included medications that fell into one of the following categories: long-term beta agonists, inhaled corticosteroids, cromolyn, and leukotriene modifiers. The table also listed commonly prescribed short-term beta-agonists and allergy medications. The response options for frequency of use were: 1) when having symptoms only, 2) when having an attack only, or 3) regularly-even when not having symptoms.
To assess factors related to access to medical care, the questionnaire included items on insurance status, access to medical advice on evenings or weekends, and whether the child had a single, usual source of asthma care. Classifications for a single, usual source of medical care for asthma included emergency departments, private physician's offices, community clinics/hospital outpatient clinics, as well as not having a single, usual source of care. If more than one location was indicated on the questionnaire, the respondent was classified as not having a single source of usual care and combined with the children who reported not having a usual source of care. The rationale for collapsing these two categories is to be able to examine consistency of care, and thus children with a single source of usual care are compared to children who visit different places for their asthma care.
Markers of quality care were derived from the NHLBI guidelines. The following are all included in the NHLBI guidelines as recommended components of quality asthma care: self-management education for the patient and/or family, either through the child's physician or other healthcare provider or program, such as community-based or school-based initiatives, follow-up visits for routine asthma-care at intervals no greater than 6 months, and creating an asthma management plan with a healthcare provider, that contains a component that addresses appropriate medication use.2
Data were weighted to represent the number of children attending public elementary schools within their respective ZIP Codes. All data analyses were conducted using the Surveymeans, Surveyfreq, and Surveylogistic procedures in SAS v9.1(SAS Institute, Cary, NC, 2003). These methods account for the clustering by school and stratification by neighborhood asthma hospitalization rate in the sampling design.
Weighted percentages of demographic characteristics of the overall sample and of the subset of children with asthma were calculated, as were the weighted prevalence of asthma and the weighted percentage of children with asthma who reported current or persistent symptoms. Long-term medication use in all children with ever asthma, current asthma and persistent asthma was calculated and compared. To determine the socioeconomic and access to care factors that were associated with long-term medication use, both unadjusted and adjusted odds ratios and corresponding 95% confidence intervals (CI) were computed using logistic regression procedures in SAS. Missing data were excluded from these calculations, and a complete case analysis was performed. The multivariate model was constructed using variables selected a priori based on literature review and plausible mechanistic theories.
Frequency of medication use was also examined in order to determine if children who reported use of a long-term control medication used it appropriately, (regularly, even when not having symptoms). A stratified analysis of weighted frequency of use, by access to care factors, was conducted to determine if using medication regularly was more common among children who reported communication and/or educational activities such as having an asthma management plan that included when to take medications regularly and either the child or parent being enrolled in an educational asthma program. Statistical comparisons between groups were made by conducting chi-square tests corrected for the study design in SAS.