Is low birth weight a risk factor for asthma during adolescence?
The effect of low birth weight on the incidence of asthma by 17 years of age was investigated by studying medical draft examination records of 20,312 male subjects born in Jerusalem between January 1967 and December 1971. Additional information on birth weight and other demographic factors was abstracted from the Jerusalem Perinatal Study computerised database. A stepwise multiple logistic regression was used to estimate the odds ratios for developing asthma by 17 years of age in 500 g birthweight categories from less than 2000 g to 4500 g. The odds ratios were adjusted for the confounding effects of ethnic origin, social class (determined by area of residence), paternal education, maternal age, and birth order. The group with low birth weights (less than 2500 g, n = 1004) had a significantly increased risk of developing asthma by 17 years of age, with an adjusted odds ratio of 1.44 (95% confidence interval (CI) 0.79 to 2.66) for birthweight group less than 2000 g and 1.49 (95% CI 1.05 to 2.12) for birthweight group 2000-2499 g compared with the reference group of 3000-3499 g. We conclude that infants with birth weights of less than 2500 g may have a higher risk of asthma during childhood and adolescence than infants who were heavier at birth.