RISK FACTORS FOR INFANT ASTHMA IN SUSCEPTIBLE FAMILIES

Transcription

1 RISK FACTORS FOR INFANT ASTHMA IN SUSCEPTIBLE FAMILIES Center for Research on Child Wellbeing Working Paper # FF Bill Chiu 1, MD Marie Crandall 1, MD, MPH Karen Sheehan 2, MD, MPH Departments of Surgery 1 and Pediatrics 2 Northwestern University Feinberg School of Medicine Corresponding Author: Marie Crandall, MD, MPH Assistant Professor of Surgery Division of Trauma and Surgical Critical Care Northwestern University 201 E. Huron St., Galter # Chicago, IL Telephone: Fax: macranda@nmh.org 1

2 RISK FACTORS FOR INFANT ASTHMA IN SUSCEPTIBLE FAMILIES 2

3 ABSTRACT Purpose: Socioeconomically disadvantaged communities in the United States have disproportionately high number of children diagnosed with asthma. We investigated risk factors contributing to the disease among children born to susceptible families. Methods: The Fragile Families and Child Wellbeing Study is a longitudinal cohort of approximately 5000 children from disadvantaged parents across the United States. Data from interviews with mothers conducted shortly after birth and follow-up surveys at one year were analyzed. Infant asthma requiring medical attention was the outcome of interest. Multivariate regression analysis identified independent risk factors for infant asthma. Results: 13.5% of the respondents (n=506 of 3747) had an infant with asthma. Significant risk factors included maternal cigarette smoking, low birth weight, infant male gender, and African American race. Breastfeeding was protective. Conclusion: Environmental factors interact with a child s characteristics in contributing to infant asthma. Policies that promote breastfeeding and discourage maternal cigarette smoking could reduce asthma incidence. Key Words: Infancy, asthma, racial disparities, smoking 3

4 Approximately 17.3 million people in the United States are estimated to have asthma 1, and one third of these affected are children 2. The prevalence of asthma is particularly high in urban, minority, and low-socioeconomic populations, and the rates have been rising 3. Despite many studies that report the overrepresentation of asthmatics in vulnerable populations 4, which risk factors can independently predict asthma diagnosis still remain to be determined. In this study, we analyze a prospectively gathered database containing interview responses from a vulnerable population. By examining how different risk factors can affect a predominantly low-socioeconomic group, we aim to identify intervention strategies that can decrease the incidence of asthma in this overburden population. 4

5 METHODS Data for this research was obtained from the Fragile Families and Child Wellbeing study. Fragile Families is a longitudinal study following approximately 5000 children nationwide born between 1998 and 2000, the majority from unmarried households. Permission to use this database was granted from the Fragile Families Collaborative, and the Northwestern University Institutional Review Board approval was obtained. Data were analyzed using STATA statistical software ( Stata Press, College Station, TX). Data from baseline interviews with the mother and follow-up interviews at one year were utilized. The outcome of interest, asthma requiring medical attention in the first year of life, was identified through self-report during the maternal follow-up interviews. The three questions were (1) whether mother was told by health care professional that child has asthma, (2) whether child ever had an episode of asthma attack, and (3) whether child was treated for asthma at a hospital emergency room. Responses to these three questions were combined to represent the outcome in our analysis. Potential risk factors for asthma were listed in Table 1A. Bivariate analyses between the individual risk factors and the asthma outcome were performed using χ 2 tests. Variables were identified as potential independent predictors of asthma or confounders by using sequential multiple regression models which included variables that yielded a p-value 0.1 on bivariate statistics. This final multivariate regression model was used to identify independent risk factors for asthma in the first year of life. A p-value <0.05 was accepted as statistically significant. 5

6 RESULTS Of the 3747 respondents, 506 mothers (13.5%) reported that their babies had infant asthma requiring medical attention during the first year of life. Of these 506 mothers, 506 (100%) were told that their children had asthma, 311 (61%) reported that their children had at least one asthma attack, and 292 (58%) had emergently brought their children to a hospital for asthma treatment. Bivariate Analysis Bivariate analyses were performed between the outcome of interest, asthma requiring medical attention during the first year of life, and potential risk factors. The risk factors which generated a p-value 0.1 included (1) breastfeeding by mother, (2) child s birth weight, (3) cigarette smoking by mother, (4) male gender of the child, and (5) African American race (Table 1). Since the database we used sampled mostly unmarried women and their babies, we did not analyze factors related to the mean income level of this population, as the socioeconomically disadvantaged were highly over-represented in our study. Multivariate Regression Analysis Using all six potential risk factors, we performed a multivariate logistic regression analysis to identify the independent risk factors for asthma in the first year of life. The same five risk factors identified in the bivariate analysis were also found to be significant in the logistic regression analysis: (1) breastfeeding by mother, (2) child s birth weight, 6

7 (3) cigarette smoking by mother, (4) male gender of the child, and (5) African American race (Table 2). Breastfeeding by mother had a protective effect against infant asthma. 7

8 DISCUSSION It is not particularly surprising that lower-income families are overrepresented with respect to infant asthma. This has been shown in other work. 5,6 Our study confirms these previous findings. What have not been elucidated to date, however, are the particular risk factors that influence this disparity. These data represent the first attempt to delineate independent predictors of infant asthma within a higher-risk population. We discovered that low infant birthweight, maternal cigarette smoking, male gender, and African American race were independent predictors of infant asthma, which confirmed the results of other studies. 7,8,9 Since maternal cigarette smoking and low birthweight are interrelated, we took care to evaluate these variables separately, and found that each exerts an independent effect on the risk of infant asthma. It appears that race and gender, irrespective of socioeconomic status, influence the occurrence of infant asthma. There exist both racial and gender disparities in asthma prevalence within the study population that are likely multifactorial, the mechanisms of which have been poorly explained and are the subject of ongoing research. In addition, breastfeeding was found to be protective in our cohort, though this has not been uniformly found in previous research. 10,11 The very high prevalence of infant asthma in our sample (more than 3x the general population risk for children under 18, 4% 12 ) indicates that a complex interplay of factors contribute to the development of infant asthma among the economically disadvantaged, possibly including environmental hygiene and dietary factors. 13 This population-based study was unable to evaluate all these potential influences, but its prospectively gathered data, ability to control for economic variables, and robust 8

9 methodology strengthen the findings. Additional limitations include the potential for recall bias inherent in survey methodology and the potential for subjectivity in diagnosis of asthma, though we attempted to minimize these by limiting our outcome of interest to physician-diagnosed asthma. The importance of this study is that it identifies potential areas for intervention that may help decrease the burden of infant asthma among lower socioeconomic status families. Maternal cigarette smoking and breastfeeding practices can be influenced by behavioral counseling and support. 14 In addition, community-based prenatal care and nutrition support are essential to decreasing the likelihood of having a low birthweight infant, which would impact a host of potential infant illnesses, not just asthma. However, further research needs to be done to better understand the roles of race and gender on the occurrence of infant asthma. Another limitation of the study is the diagnosis of infant asthma. This diagnosis is difficult to make in an infant, and wheezing in infants may also be caused by other obstructive process in the airway ranging from allergic rhinitis, vocal cord dysfunction, vascular rings or laryngeal webs, or bronchopulmonary dysplasia. The NIH recognizes that infant asthma is both under- and over-diagnosed, and its diagnosis is hampered by the difficulty of obtaining objective measurements of lung function in this age group. A systematic approach, including a stepwise implementation of medications, based on symptoms, is currently recommended. 15 However, this is a challenge to all researchers studying infant asthma, and by examining infants who were similarly diagnosed, our study can focus on a more homogenous group to identify population-specific risk factors. In summary, this study has identified potentially modifiable risk factors that influence the appearance of infant asthma in an already-overburdened population. By 9

10 investing resources into community-based education and support services, we can help decrease the impact of the morbidity of infant & childhood asthma among the underserved. 10

11 REFERENCES 1. Rappaport S, Boodram B. Forecasted state-specific estimates of self-reported asthma prevalence-united States MMWR 1998;47: Benson V, Marano M. Current estimates from the National Health Interview Survey, Vital Health Stat. 10 (199). Hyattsville, MD: Natl. Cent. Health Stat. 3. Aligne CA, Auinger P, Byrd RS, et al. Risk factors for pediatric asthma: contributions of poverty, race, and urban residence. Am J Resp Crit Care Med 2000;162: Christiansen SC, Martin SB, Schleicher NC, et al. Current prevalence of asthmarelated symptoms in San Diego s predominantly Hispanic inner city children. J Asthma 1996;33: Weiss KB, Gergen PJ, Wagener DK. Breathing better or wheezing worse? The changing epidemiology of asthma morbidity and mortality. Ann Rev Public Health 1993;14: Weiss KB, Gergen PJ, Hodgson TA. An economic evaluation of asthma in the United States. NEJM 1992;326: Sin DD, Spier S, Svenson LW, et al. The relationship between birth weight and childhood asthma: a population-based cohort study. Arch Pediatr Adolesc Med, 2004;158(1):

12 8. Strachan DP, Cook DG. Health effects of passive smoking. 6. Parental smoking and childhood asthma: longitudinal and case-control studies. Thorax. 1998;53: Nelson DA, Johnson CC, Divine GW, et al. Ethnic differences in the prevalence of asthma in middle class children. Ann Allergy Asthma Immunol. 1997;78: Dell S, To T. Breastfeeding and asthma in young children: findings from a population-based study. Arch Pediatr Adolesc Med, (11): Rust GS, Thompson CJ, Minor P, et al. Does breastfeeding protect children from asthma? Analysis of NHANES III survey data. J Natl Med Assoc, 2001;93(4): Akinbami LJ, Schoendorf KC, Parker J. US childhood asthma prevalence estimates: the impact of the 1997 National Interview Survey Redesign. Am J Epi 2003;158: Gold DR, Rotnitzky A, Damokosh AI, et al. Race and gender differences in respiratory illness prevalence and their relationship to environmental exposures in children 7 to 14 years of age. Am Rev Resp Dis 1993;148: Albrecht SA, Higgins L, Lebow H. Smoking cessation counseling for pregnant women who smoke: scientific basis for practice for AWHONN's SUCCESS project. J Obstet Gynecol Neonatal Nurs, 2004;33(3): National Institutes of Health. Expert Panel 2: Guidelines for the Diagnosis and Management of Asthma NIH, National Heart, Lung, Blood Institute. Accessed 9/06 12

13 Table 1 Bivariate Analysis Risk Factor p-value Asthma Outcome Breastfeeding Yes 2467 (57%) 0.1 No 1864 (43%) Low Birth Weight Yes 484 (10%) 0.1 No 4276 (90%) Maternal Smoking Yes 1159 (27%) 0.1 No 3203 (73%) Infant Gender Male 2538 (53%) 0.1 Female 2261 (47%) Race White 1480 (31%) 0.1 Black 2390 (50%) Asian 133 (2.8%) American Indian 222 (4.6%) Other 580 (12%) Table 2 Multivariate Analysis Risk Factor Odds Ratio 95% CI p-value Breastfeeding Low Birth Weight Maternal Smoking Male Gender <0.001 African American Race <

14 TABLE LEGENDS Table 1: Bivariate analysis between the outcome of infant asthma and six potential risk factors. Table 2: Multivariate regression analysis between the outcome of infant asthma and six potential risk factors. The odds ratio, 95% confidence interval (CI), and p-value associated with each risk factor are listed. 14