J ALLERGY CLIN IMMUNOL

FEBRUARY 2011

AB80 Abstracts

SUNDAY

297 The Influence of Cesarean section on the Incidence ofChildhood Asthma: A Propensity Score Approach

B. Kim1,2, R. Qin3, S. Katusic3, Y. J. Juhn1; 1Department of Pediatric and

Adolescent Medicine Mayo Clinic, Rochester, MN, 2Department of Pedi-

atrics, Gangneung Asan Hospital, University of Ulsan College of Medi-

cine, Gangneung-Si, KOREA, REPUBLIC OF, 3Department of Health

Sciences Research Mayo Clinic, Rochester, MN.

RATIONALE: In an observational study assessing the role of mode of de-

livery (vaginal delivery vs. cesarean section) at birth in subsequent risk of

asthma, which cannot be assigned randomly, covariate imbalance between

comparison groups is a significant obstacle.

METHODS: The study was designed as a retrospective cohort study.

Study subjects were all children born in Rochester, Minnesota, between

1976 and 1979. Asthma status during the first 6 years of life was deter-

mined by applying predetermined criteria. The propensity scores were for-

mulated using 16 covariates using a logistic regression model for mode of

delivery. The cumulative incidence of asthma between comparison groups

was calculated using Kaplan-Meier curve and log-rank test was used to test

statistical significance.

RESULTS: There were significant covariate imbalance between groups of

children born by cesarean sectionvs. vaginal delivery that include the num-

ber of prenatal visits, birth weight, ethnicity, complication during preg-

nancy, complication during labor, induction, maternal age, a family

history of atopy, and maternal smoking history. After matching with pro-

pensity scores, imbalance of these covariates reduced and became statisti-

cally not significant. We found that children born by cesarean section had a

similar risk to the matched children born by vaginal delivery (2.1% vs.

2.5%, p50.79).

CONCLUSIONS:Mode of delivery is not associated with risk of asthma

during the first six years of life. The propensity score method is a useful

tool for addressing covariate imbalance in an observational study concern-

ing risk factors in asthma epidemiology.

298 Patient and Physician Differences in Understanding AsthmaSymptom Deterioration Terminology From the Asthma Insightand Management (AIM) Survey

D. E. Doherty1, E. O. Meltzer2, S. W. Stoloff3, K. R. Murphy4, R. A. Na-

than5, M. Blaiss6; 1Division of Pulmonary, Critical Care, and Sleep

Medicine, University of Kentucky, Lexington, KY, 2Allergy and Asthma

Medical Group and Research Center, San Diego, CA, 3University of Ne-

vada School of Medicine, Reno, NV, 4Boys Town National Research Hos-

pital, Boys Town, NE, 5Asthma and Allergy Associates, P.C. and Research

Center, Colorado Springs, CO, 6University of Tennessee Health Science

Center, Memphis, TN.

RATIONALE: The 2009 Asthma Insight and Management (AIM) survey

was a large and comprehensive national survey of asthma patients, physi-

cians, and the general population that assessed the status of asthma burden

and management in the US. Because patient-physician communication is a

critical component of successful asthma management, we compared AIM

data showing patient- and physician-reported familiarity and use of termi-

nology used to describe asthma symptom deterioration.

METHODS: Phone interviews were conducted in a national random

sample of 2500 asthma patients aged >_12y (60,682 households screened)

and 309 physicians (allergists5104; family practitioners5101;

pulmonologists554; internists550).

RESULTS: ‘‘Exacerbation’’ is the term used most commonly by physi-

cians (77% vs ‘‘flare-up’’570% and ‘‘attack’’565%) but is least familiar

to patients (24%). ‘‘Attack’’ is familiar to 97% of patients but used by

only 65% of physicians (57%-74% across specialties). Concordance in

use and familiarity was highest for ‘‘flare-up’’ (physicians570% [57%-

78% across specialties]; patients571%). ‘‘Exacerbation’’ and ‘‘flare-up’’

were considered similar by 94% of physicians (90%-98% across special-

ties) but only 38% of patients. ‘‘Attack’’ was considered the same as

‘‘asthma exacerbation’’ or ‘‘flare-up’’ by 65% of physicians, but only

36% of patients. For patients (n51555) and physicians (n5107) who did

not believe these termswere the same, 18% vs 50%, respectively, described

an asthma attack as ‘‘more sudden,’’ and 17% vs 55% described an asthma

attack as ‘‘more severe’’ than ‘‘exacerbation/flare-up.’’

CONCLUSIONS: Results from the AIM survey suggest a substantial

communication gap exists between physicians and patients in familiarity

and use of asthma symptom deterioration terminology, which may under-

mine optimal asthma management.

299 Association of Obesity with Asthma in Japanese PreschoolChildren

Y. Adachi1, T. Itazawa1, Y. S. Adachi1, Y. Ito1, Y. Okabe1, K. Yoshida2, Y.

Ohya2, H. Odajima3, A. Akasawa4, T. Miyawaki1; 1Department of Pediat-

rics, University of Toyama, Toyama, JAPAN, 2National Center for Child

Health and Development, Tokyo, JAPAN, 3Fukuoka National Hospital,

Fukuoka, JAPAN, 4Tokyo Metropolitan Children’s Medical Center,

Tokyo, JAPAN.

RATIONALE: Obesity may increase the risk of subsequent asthma. We

have previously reported a clear association between obesity and asthma

in Japanese school-aged children.

METHODS: To evaluatewhether the similar association exists in younger

children, a cross-sectional and ISAAC questionnaire-based survey was

performed among children aged 4-5 years. A child who had experienced

wheezing during the past 12 months and had ever diagnosed as asthma

by a physician was defined as having current asthma. Overweight and un-

derweight was defined as BMI >_90th and <_10th, respectively, according to

the reference values for Japanese children during 1978 to 1981.

RESULTS: After omitting 547 incomplete data, 34,699 children were an-

alyzed. Current asthma was found in 10.5% of underweight, in 11.1% of

normoweight, and in 13.2%of overweight children. Therewas a significant

association between overweight and asthma (p<0.001). This association

still remained even after adjusted for other variables, such as gender,

coexisting other allergic diseases, and parental history of asthma (adjusted

OR: 1.22, 95% CI: 1.10-1.37, p<0.001).

CONCLUSIONS: Even in preschool children, obesity may already asso-

ciate with asthma. Physicians should consider the impact of obesity when

managing asthma in younger children.

300 Risk of Asthma in Former Late Preterm Infants: A PropensityScore Approach

G. A. Matthews, R. Qin, S. K. Katusic, Y. J. Juhn; Mayo Clinic, Roches-

ter, MN.

RATIONALE: The risk of asthma in former late preterm infants has not

been well defined. The propensity score approach allows us to evaluate

the impact of being a former late preterm infant while controlling for

covariate imbalance.

METHODS: The study was designed as a retrospective cohort study.

Study subjects were all children born in Rochester, Minnesota between

1976 and 1982. Asthma status during the first six years of life was assessed

by applying predetermined criteria. The propensity score was formulated

using 16 covariates by fitting a logistic regression model for late preterm

birth versus term birth. We applied the propensity score method to match

late preterm infants (34 0/7 to 36 6/7 weeks gestation) to term infants

(37 0/7 to 40 6/7 weeks gestation) within a caliper of 0.2 standard deviation

of logit function of propensity score.

RESULTS: Of the 7,040 infants, 52% were male and 94% were

Caucasians. Before matching, late preterm infants had a higher risk of

asthma (27 of 333, 8.1%) compared to full term infants that developed

asthma (314 of 6,707, 4.7%) (p50.004). There was significant covariate

imbalance between comparison groups. After matching with propensity

scores, we found that former late preterm infants had a similar risk of

asthma to the matched full term infants (7.1% vs. 8.7%, respectively,

p50.64). Covariate imbalance was greatly reduced.

CONCLUSIONS: Being a former late preterm infant is not associated

with a risk of asthma. The propensity score method is a useful tool in ad-

dressing covariate imbalance.