528 - A Study of the Relationship Between Low Birth Weight Infants and Childhood Respiratory Diseases: 21st Century Longitudinal Survey in Japan

Publication Number: 528.3591

Ryo Nishiguchi, National Hospital Organization Nagasaki Medical Center, 2-1001-1, Kubara, omura, Nagasaki, Japan; Fumihiko Namba, Saitama Medical Center, Saitama Medical University, Kawagoe, Saitama, Japan

Background: A low birth weight infant (LBWI) may be a risk factor for respiratory diseases such as bronchial asthma (BA) and respiratory tract infections (RTI) in childhood. Nevertheless, this hypothesis has yet to be fully corroborated by epidemiological evidence in Japan.

Objective: The objective of this study was to assess the risk of childhood respiratory disease in low-birth-weight infants using data on children aged 0 to 11 years old in the Longitudinal Survey of Newborns in the 21st Century, which was conducted by the Japanese Ministry of Health, Labour and Welfare.

Design/Methods: The Newborns Survey included all infants born in Japan during the periods January 10–17, 2001, and July 10–17, 2001, using national birth records (n = 53,575). Questionnaires were mailed and 47,001 people responded. Follow-up surveys were conducted every year. The data were corrected for lifestyle factors (e.g., sibling, daycare attendance, nutrition type, and smoking status), rates of hospital visits and hospitalization due to BA and RTI by age (1, 3, 5, 7, 9, and 11 years). To estimate the risk of LBWI, the group was stratified by BW according to categories: BW(1) < 1000 g, (2) 1000-1499 g, (3) 1500-2499 g, and (4) ≥ 2500 g. The outcome data were analyzed using Fisher’s exact test, Pearson’s chi-square test, and the Mann-Whitney U test, as appropriate. Multivariate regression models were applied with adjustment for factors.

Results: The number of individuals in each BW group for whom responses were obtained was as follows: BW (1) 84, (2) 196, (3) 3,725, and (4) 42,996. The rate of hospital visits for RTI at each age did not differ by BW, but the rate of hospitalization for RTI was higher in the group of preschool children with a BW below 1500 g. The adjusted odds ratios (ORs) and 95% confidence intervals (CIs) at 5 years of age were BW(1) ORs 7.86 (95% CI 3.30-18.7) and (2) 3.07 (95% CI 1.4-6.70), using (4) as a reference. The rate of hospital visits for BA tended to decrease in school age, even in the LBW group. However, in the BW(1) group, the rate was higher in school age than in infancy (Figure 1). The adjusted ORs and 95% Cls at each age were as follows: OR 2.39 (95% CI 1.12-5.09) at age 7, OR 3.15 (95% CI 1.47-6.77) at age 9, and OR 3.03 (95% CI 1.27-7.21) at age 11 in the BW(1) group.

Conclusion(s): This is the inaugural large-scale cohort study in Japan to examine the risks of RTI and BA in LBW group. For BA, the risk persists into the school-age years, particularly in infants with extremely low birth weight, and our findings also indicate the necessity for long-term follow-up of respiratory function.

Hospital visits for asthma by birth weight at each age
Birth weight (BW) categories: BW (1) < 1000 g, BW (2) 1000-1499 g, BW (3) 1500-2499 g, and BW (4) ≥ 2500 g
The rate of hospital visits for Bronchial asthma tended to decrease in school age, even in the LBW group. However, in the BW (1) group, the rate was higher in school age

Hospital visits for asthma by birth weight at each age
Birth weight (BW) categories: BW (1) < 1000 g, BW (2) 1000-1499 g, BW (3) 1500-2499 g, and BW (4) ≥ 2500 g
The rate of hospital visits for Bronchial asthma tended to decrease in school age, even in the LBW group. However, in the BW (1) group, the rate was higher in school age