Purpose of the Study. To study the contribution of low birth weight to the prevalence of asthma in children under 4 years old in the United States.
Study Population. A total of 8071 children on whom data was collected in the 1988 National Maternal-Infant Health Survey (NMIHS) and the 1991 Longitudinal Follow-up Survey. The NMIHS collected data from the primary caretakers of a set of children born in the United States in 1988, and then follow-up information was collected in their third year of life. African American and low birth weight infants were oversampled, increasing their representation in the database. Data were weighted to be nationally representative.
Methods. The primary endpoint was whether a health care provider had ever told the primary caretaker that the patient had asthma. Data on birth weight, sex, race, maternal age, maternal education and socioeconomic status, maternal smoking, and poverty were also collected. Birth weight was stratified to very low birth weight (VLBW) (<1500 g), moderately low birth weight (1500–2499 g), and not low birth weight (LBW). Data were then analyzed to determine relative contributions of birth weight and other factors to development of asthma.
Results. The prevalence of asthma was higher at lower birth weights: 6.7% in children weighing >2500 g at birth, 10.9% in children weighing 1500 to 2499 g at birth, and 21.9% in children weighing <1500 g at birth. Birth weight was independently associated with prevalence of asthma, as was African American race. Although LBW and VLBW infants had similar risks of developing asthma regardless of race, the prevalence of VLBW was tripled in African Americans.
Conclusions. These data identify a strong association between LBW and asthma. A total of 4000 excess asthma cases were attributable to LBW. The substantially increased prevalence of VLBW in the African American community may contribute to the higher prevalence of asthma in this community.
Reviewers’ Comments. The major weakness of this study is that it relies on retrospective data reported by the primary caretaker. The only measure of asthma used was the answer to a single question on whether the child had ever been diagnosed with asthma by a health care professional. This measure may simultaneously miss some patients in whom the caretaker failed to recall the diagnosis of asthma and overcount some patients who do not actually have asthma. Nonetheless, the data is compelling and supportive of other studies. These results provide another reason for improving prenatal care to prevent LBW and VLBW births and also suggest we should be targeting the LBW and VLBW children for asthma screening and early intervention with asthma therapies.
- Copyright © 2002 by the American Academy of Pediatrics