OBJECTIVE. We conducted a national, population-based survey to examine the asthma-related health burden of US children.
METHODS. A telephone-based survey was conducted in 2004 of children 4 to 18 years of age with current asthma in the United States. In 41433 households screened, 1089 children reported current asthma; 801 interviews were completed by parents of children aged 4 to 15 years and by children themselves aged 16 to 18 years. The survey included questions about symptoms, perceived level of control, activity limitations, health care use, medicines, disease management, and knowledge. Global asthma symptom burden, derived from the National Asthma Education and Prevention Program guidelines, was composed of 3 components: short-term symptom burden (4-week recall), long-term symptom burden (past year), and functional impact (activity limitation).
RESULTS. The majority of children were classified with mild intermittent disease on the basis of recent daytime symptoms alone (80%); yet, when report of nighttime symptoms was included, the proportion of children classified as having mild intermittent symptoms decreased (74%). When asthma burden was assessed on the basis of the global symptom burden construct, only a minority (13%) of individuals was classified as having an asthma symptom burden consistent with mild intermittent disease; the majority (62%) was classified as having moderate/severe disease. In addition, the impact of asthma on the daily activities is substantial; avoiding exertion (47%) and staying inside (34%) are common approaches to improve control of asthma symptoms.
CONCLUSIONS. The goals of therapy for asthma, based on the National Asthma Education and Prevention Program guidelines, have not been achieved for the majority of children. In addition, parents and children overestimate the child's asthma control and commonly restrict activities to control asthma symptoms. Deficiencies in the control of asthma may be related to the underestimation of the burden of disease.
Despite effective treatment and an improved understanding of the pathogenesis and pathophysiology of asthma, asthma is associated with high morbidity and significant mortality.1,2 In 2002, children with asthma reported 5 million asthma-related health care visits, 727000 emergency department visits, 196000 hospitalizations, and missed 14.7 million school days because of asthma, and there were 187 pediatric deaths.3 With ∼200000 hospitalizations annually among children, asthma is the third leading cause of preventable hospitalization.4 These figures demonstrate that asthma is a large and growing public health problem; however, there is a common misperception that asthma is a mild, non-life-threatening ailment.
Evidence supports the regular use of inhaled corticosteroids for long-term improvement of outcomes such as symptoms scores, lung function, and health care use for children with persistent asthma.5,6 Current guidelines recommend inhaled corticosteroids for all children with persistent disease, yet studies continue to show that many children who should receive controller therapy do not.7–9
Reasons for continued underuse are multifactorial, but one factor may be related to difficulties experienced by children and their parents in communicating the impact of the disease on children's daily activities. Previous studies among adults with asthma emphasize that the distribution of burden is greatly influenced by the type of symptom reports used in a classification system.10 In addition, discordance in type of asthma symptoms reported by individual subjects suggests that the quantification of the burden of asthma is related to how the National Asthma Education and Prevention Program (NAEPP) classification is operationalized and may contribute to low appreciation of disease burden and subsequent poor use of controller medication. The current report uses data obtained as part of the 2004 Children and Asthma in America Survey to examine whether the results among adults in previous surveys11 can be extrapolated to pediatric asthma populations.
The data for this study come from a national probability sample of parents and their 4- to 18-year-old children with current asthma in 2004 identified using random digit dialing. Children were classified as having current asthma if they had ever been diagnosed by a physician as having asthma and either were taking medication for their asthma or had asthma symptoms in the past year. Telephone interviews of 41433 households were conducted by trained interviewers to identify 1089 children with current asthma. Among age-eligible children with current asthma (N = 1089), the interview was successfully completed in 73.6%; the majority of the subjects who did not complete the interview were awaiting callback (21.2%) at the time the target recruitment was met. Among a minority of age eligible children, only a partial interview was completed (5.2%). Surveys were completed by parents of children ages 4 to 15 years (84.6%) and directly by the children ages 16 to 18 years (15.4%; Fig 1).
Patient screening and interviews were conducted between February 25, 2004, and May 7, 2004. Survey items covered the following areas: sociodemographics; symptoms; medications; perceived level of asthma control; physical activity limitations; health care use; disease management; and knowledge, attitudes, and beliefs regarding asthma and asthma therapy.
For analyses comparing the current results to survey data obtained from 1998, we used the 1998 Asthma in America Survey. The 2004 questionnaire overlapped significantly with the 1998 instrument and also included several questions on nasal allergies and sources of information about asthma. The 1998 survey was performed with similar methodology, which has been reported previously in detail.11 To allow comparison with the current analysis, we have limited the 1998 data to the subpopulation of children 4 to 18 years and their parents who responded to the survey (N = 758).
Asthma Burden Classification
Asthma symptom burden was evaluated as 3 components: short-term symptom burden, long-term symptom burden, and global symptom burden as defined previously.11 The criteria for categorizing asthma symptom burden were based on the NAEPP Expert Panel II recommendations for assessing asthma severity.10 Moderate and severe persistent asthma were combined to create 3 categories of increasing burden (mild intermittent, mild persistent, and moderate/severe persistent). Consistent with the NAEPP Expert Panel II criteria, individuals were assigned to the highest grade in which any feature occurred. Although asthma symptom burden is a component of asthma severity assessment, the 2 are distinct concepts. The NAEPP guidelines specifically outline that the categorization of severity is accurate only before the initiation of controller therapy; among prevalent cases of asthma (already on therapy), persons with different underlying disease severity can achieve similar levels of symptom burden, they will just require different levels of controller therapy to achieve the same level of burden. Our analysis focused on asthma symptom burden only, and current level of medication use was not incorporated into the assessment. In addition, no lung function data were available; therefore, forced expiratory volume in 1 second (FEV1) values were not incorporated into the assessment of asthma burden.
Short-term symptom burden was categorized on the basis of reported daytime and nocturnal symptoms over the past 4 weeks. Long-term symptom burden included the recall of average weekly symptoms and the frequency of asthma exacerbations recalled over a 12-month period. Functional impact included 3 components, physical, social, and nocturnal impact of asthma, each graded on a 4-point Likert scale from 0 (none) to 3 (a lot). The global-symptom burden construct combined short-term symptom burden, long-term symptom burden, and functional impact.
The outcome of interest was the distribution of asthma symptom burden. We examined the association between asthma symptom burden and sociodemographic variables and medication use. Differences in the proportions were assessed for significance by χ2 tests.
Among surveyed households with children ages 4 to 18 years, the prevalence of pediatric asthma (ever diagnosed) was 15.7%. Among children who ever received a diagnosis of asthma, 81.7% and 16.2% reported current asthma and past asthma, respectively; an additional 2.1% reported that they were not sure of the current status. These results yielded a population prevalence of current asthma in children <19 years of age of 9.2% among children screened for asthma (N = 18963; Fig 1).
The age of the population with current asthma in the sample (N = 801) was evenly distributed, with 55.3% ages 4 to 11 years and 44.7% ages 12 to 18. The majority of the population was white non-Hispanic (62.2%) and had parents with a high school (46.7%) or higher level (50.4%) of education. The majority had employer-based health insurance (57.3%), with 26.2% reporting Medicaid coverage and 14.7% self-insured; 6% reported that the child was not covered by any health insurance. Income was evenly distributed among the categories evaluated. Thirty-six percent of the children with asthma reported exposure to tobacco smoke in the home (personal or passive exposure), and 56% reported having a pet in the home (Table 1). There were no significant differences in the distribution of demographic characteristics across the categories of asthma symptom burden, except that children with moderate/severe disease tended to be lower income and have self-pay insurance status (Table 1).
Discordance in Assessment by Measures of Symptom Burden and Distribution of Disease Stratified by Measures of Burden
The distribution of disease burden classification was highly dependent on the definitions applied. On the basis of daytime symptoms alone, the majority of children were classified with mild intermittent symptom burden (80%), with only a minority being labeled with moderate/severe persistent symptom burden (9%). However, when report of nighttime symptoms was included in the assessment of short-term symptom burden, the proportion of children classified as having moderate/severe persistent symptoms increased considerably (26%). When long-term symptoms are included, the proportion classified as having mild intermittent burden decreased further (51%), whereas the proportion having mild persistent and moderate/severe burden increased (21% and 29%, respectively). Furthermore, the impact of asthma on daily activities is substantial; a dramatically higher proportion of children were classified as having moderate/severe persistent disease (62%) when functional impact was included in the assessment. Parents and their children reported that limitation of activities (47%) and staying inside (34%) are a common approach to improve control of asthma symptoms (data not shown). Finally, on the basis of the global symptom burden construct derived from the NAEPP guidelines, only a minority (13%) of individuals were classified as having an asthma symptom burden consistent with mild intermittent disease, the majority (62%) being classified as having moderate/severe disease (Fig 3A).
Among the population of children with current asthma, individuals are discordant in the type of short-term symptoms reported (Fig 2). Of the children who reported short-term symptoms (symptoms in the past 4 weeks, N = 537), only 28% of children reported symptoms in all 3 of the categories: daytime symptoms, nocturnal awakenings, and activity limitation simultaneously. Just over a third (37.8%) reported 2 of the 3 symptom components, whereas an additional third (34.3%) reported only a single symptom over the last 4 weeks.
Furthermore, disparity in how children and their parents perceive the level of asthma control also influences the assessment of asthma health status; many children and their parents perceive a higher level of control than exists when categorized by more detailed questions about the level of symptom burden. There was significant discordance between the children's (or their parents') report of level of control and their overall level of asthma symptom burden based on the global asthma symptom burden assessment. Among the children who met criteria for moderate/severe persistent symptom burden, more than half (54%) reported that their asthma was well or completely controlled, whereas only a minority (6%) reported that their asthma was poorly controlled or not controlled at all when asked specifically about their overall level of control (data not shown).
When the 2004 survey was compared with the 1998 Asthma in America Survey (restricted to children ≤18 years of age), the overall results were similar; the majority of children or their parents report symptom burden compatible with persistent disease. There was a trend toward an increase in the overall symptom burden over the 6-year period, with 55% vs 62% reporting moderate or severe persistent symptom burden in 1998 and 2004, respectively (Fig 3B).
Our results document that the goals of therapy for asthma, based on the NAEPP guidelines, have not been achieved for the majority of children with asthma, and deficiencies in the use of specific criteria may be related to the underestimation of the level of control in patients. Using the construct of global asthma symptom burden, a minority (13%) of children was classified as having an asthma symptom burden consistent with mild intermittent disease, whereas 62% had moderate/severe persistent disease. Although 80% of children were classified as having mild intermittent disease on the basis of recent daytime symptoms alone, only 64% remained categorized as mild intermittent when recent nighttime symptoms were added. Assessment of symptoms over a longer period (more than the last 4 weeks) further influenced the distribution of symptom burden of asthma. However, incorporation of the functional impact term with its focus on activity limitation has the greatest impact on the distribution of symptom burden among the population.
The continued shift in the overall distribution with incorporation of each additional component highlights the large discordance between the level of burden captured by the individual components of asthma symptom burden (short-term symptoms versus long-term symptoms or activity limitation [functional impact]). The consistent pattern seen comparing the distribution between the 1998 and 2004 data strengthens the importance of the issue; the variation in the pattern of asthma symptoms reported by individual subjects can influence the estimate of the burden of disease in children. Accurate assessment of asthma status requires a combination of parameters and may depend on which parameters are used. The common measures of asthma morbidity are not interchangeable. Juniper et al12 recently published a factor analysis using the data available from 3 large clinical trials. The analysis explored whether conventional clinical outcomes used in defining asthma severity and asthma control (symptom severity, airway caliber, and rescue β agonist use, in addition to health-related quality of life) measure a single concept or whether they assess distinct components of disease status. The analysis demonstrated that, although there is some correlation between the available measures, asthma health status has 4 components (factors; asthma-specific quality of life, airway caliber, daytime symptoms, and nighttime symptoms) and that these 4 items contribute independent information to the assessment of asthma health status. Similarly, Bacharier et al13 observed a mismatch among symptoms, medication use, and lung function when assessing severity. When asthma severity was based on the higher severity of asthma symptom frequency or medication use instead of asthma symptoms alone, the proportion of children meeting criteria for mild intermittent asthma decreased 39.3% to 6.9%. In contrast, the proportion of children with moderate or severe persistent disease increased, 15.1% to 22.4% and 16.9% to 42.9% for moderate persistent and severe persistent, respectively. In addition, the majority of patients at each level of severity had FEV1 percent predicted ≥80%, and only 6.5% of patients with moderate persistent asthma had an FEV1 percent predicted of <80%. Furthermore, only 16% of patients with severe persistent asthma had FEV1 <80% predicted, and only 3.5% had FEV1 of <60% predicted. These results support the discordance in individual components in assessing asthma health status.
Variability over time must also be considered in the assessment of disease activity. Asthma is an episodic disease, and a classification system based only on symptoms over the last 4 weeks should be expected to give a different estimate of the overall burden of disease among children than one that incorporates symptoms over a longer time frame. In reanalysis of data from patients enrolled in 2 clinical trials, Calhoun et al14 evaluated how frequently asthma status changes over time. During the 12-week study, patients receiving placebo exhibited pronounced fluctuations in asthma severity and moved frequently between severity categories; the majority of patients moved between categories at least twice, with only 1 patient remaining stable over the entire 12-week period. Similarly, Stempel et al15 examined the patterns of asthma control recorded over 3 years using administrative claims and resource use definition. The authors stratified the cohort of asthma subjects based on criteria for asthma control during the initial 12 months of observation and then followed the population for an additional 2 years. Although the proportion of uncontrolled patients remained relatively constant over the subsequent 2-year period, the specific patients that populated the uncontrolled group were not constant. During the 3 years of observation, 73% of all study subjects met the criteria for uncontrolled asthma during at least one 3-month period. Asthma control frequently changes over time.
Of particular importance to pediatric populations is our finding of the shift in the distribution of symptom burden by inclusion of specific questions on activity limitation. Our results in a pediatric population differ from those obtained from a similar survey performed in Europe.16 Results from the Asthma Insights and Reality in Europe study suggest that a larger proportion of children (54.1%) have mild intermittent asthma. Although the Asthma Insights and Reality in Europe study did incorporate the frequency of symptoms with exercise into their assessment of asthma burden, they did not include questions regarding the overall assessment of activity limitation because of asthma into their classification. Independent of our categorization of activity limitation, nearly one fifth (18%) of children reported “a lot” of activity limitation and more than half (53.3%) reported at least “some” limitation in activity secondary to asthma.
The goals of therapy for asthma clearly emphasize the prevention of troublesome symptoms and recurrent exacerbations and the maintenance of normal or near normal lung function but also stress the goal of little or no impact on activity. Of particular concern is our finding that avoiding exertion and staying inside are “common approaches to improve control of asthma symptoms.” Furthermore, when asked, children report that being able to participate in activities is very important to them; almost three quarters of the children reported that organized sports or exercising and outdoor activities are extremely or very important activities. This result underscores the importance of not only asking children or their parents about their level of symptoms but also simultaneously assessing the level of activity. Children may report few symptoms; yet, if the child avoids exertion to keep his/her asthma controlled, we will overestimate the level of control for such children. Among this general population sample, more than half of the children or their parents reported limitation of a child's activity because of asthma.
We must consider limitations of our classification of asthma symptom burden. The NAEPP guidelines list activity limitation as a component of their severity classification. However, the criteria are not specifically defined, and the breakdown of severity levels for our analysis could be based only loosely on specific criteria outlined within the guidelines. However, the level of activity limitation demonstrated among children with asthma suggests that the goals of asthma therapy to “maintain normal activity levels (including exercise and other physical activity),” are not being met.10
In addition, our classification was based solely on self-reported information; no spirometry were available. However, the NAEPP criteria recommend that individuals be assigned to the highest grade in which any feature occurs; the addition of lung function measurements would serve only to increase the proportion of children classified with persistent asthma. Third, children included in this survey may have been receiving controller medication at the time that they were surveyed; this could cause the reported symptom burden to underestimate the true symptom burden of this population. Finally, the survey was limited to households with telephones. However, the Federal Communications Commission report on telephone subscribership in 2005 found that the telephone subscriber penetration rate in the United States was 94.0%.17
The overall goals for therapy are the same for all individuals with asthma; we should be able to prevent troublesome symptoms and recurrent exacerbations and maintain normal or near normal lung function and activity levels while minimizing adverse effects. To achieve these goals, clinicians need to accurately assess the level of control by questioning patients and their parents about a variety of symptoms and activity limitations and then tailor therapy and individual action plans to the specific needs and circumstances of the child.
Dr Fuhlbrigge is supported by a Mentored Clinical Scientist Development Award from the National Heart, Lung, and Blood Institute (1 K08 HL003910).
- Accepted March 2, 2006.
- Address correspondence to Anne L. Fuhlbrigge, MD, MS, Channing Laboratory, Brigham and Women's Hospital, 181 Longwood Ave, Boston, MA 02115. E-mail:
Financial Disclosure: Analysis and conduct of the survey was funded by GlaxoSmithKline (GSK), Research Triangle Park, NC. Dr Fulbrigge has received honoraria for continuing medical education (CME) lectures from GSK and Sepracor; is a consultant to GSK, Merck, and Sepracor; has received research support from Boehringer Ingelheim; and is a member of the Data Safety Monitoring Board for a industry-sponsored clinical trial (Sepracor). Dr Guilbert is a consultant for GSK and has received grants/research support from GSK, and Genetech. She has received honoraria for lectures from GSK, Astra-Zeneca (AZ), SOMA medical education (CME programs), Innovia Educational Institute (CME programs), Antidote (formerly World Medical Conferences CME programs), and the Exchange Program Steering Committee Member, which designs CME educational programs for asthma. Dr Spahn has received honoraria from GSK and AZ; is a consultant to GSK and AZ; and has received research support from GSK, AZ, and Merck. Dr Peden is a consultant for GSK and is principal investigator for a clinical trial sponsored by GSK. Dr Davis is employed by GSK.
- ↵Gergen PJ, Mullally DI, Evans RR. National survey of prevalence of asthma among children in the United States, 1976 to 1980. Pediatrics.1988;81 :1– 7
- ↵Taylor WR, Newacheck PW. Impact of childhood asthma on health. Pediatrics.1992;90 :657– 662
- ↵National Center for Health Statistics. Asthma Prevalence, Health Care Use and Mortality, 2002. Center for Disease Control. Available at: www.cdc.gov/nchs/products/pubs/pubd/hestats/asthma/asthma.htm. Accessed February 14, 2006
- ↵Adams RJ, Fuhlbrigge A, Finkelstein JA, et al. Impact of inhaled antiinflammatory therapy on hospitalization and emergency department visits for children with asthma. Pediatrics.2001;107 :706– 711
- ↵Diaz T, Sturm T, Matte T, et al. Medication use among children with asthma in East Harlem. Pediatrics.2000;105 :1188– 1193
- Ordonez GA, Phelan PD, Olinsky A, Robertson CF. Preventable factors in hospital admissions for asthma. Arch Dis Child.1998;78 :143– 147
- ↵National Institutes of Health. National Asthma Education and Prevention Program Expert Panel Report 2: Guidelines for the Diagnosis and Management of Asthma. Bethesda, MD: National Institutes of Health; 1997: Pub. No. 97–4051
- ↵Juniper EF, Wisniewski ME, Cox FM, Emmett AH, Nielsen KE, O'Byrne PM. Relationship between quality of life and clinical status in asthma: a factor analysis. Eur Respir J.2004;23 :287– 291
- ↵Rabe KF, Vermeire PA, Soriano JB, Maier WC. Clinical management of asthma in 1999; the Asthma Insights and Reality in Europe (AIRE) study. Eur Respir J.2000;16 :802– 807
- ↵Federal Communications Commission. Telephone Subscribership Report. 2005. Available at: www.fcc.gov/wcb/stats. Accessed February 14, 2006
- Copyright © 2006 by the American Academy of Pediatrics