Breastfeeding and childhood asthma: a six-year population-based cohort study

The authors elaborated the optimal duration of breastfeeding with respect to the risk of asthma primarily, and secondarily to the risk of persistent wheezing, cough and phlegm in school age in a population-based cohort study with the baseline in 1991 and follow-up in 1997. The study population comprised 1984 children aged 7 to 14 years at the end of the follow-up (follow-up rate 77). Information on breastfeeding was based on the baseline survey and information on the health outcomes at the follow-up.There was a U-shaped relation between breastfeeding and the outcomes with the lowest risk with breastfeeding from four to nine months for asthma and seven to nine months for persistent wheezing, cough and phlegm.Our results suggest a U shape relation between duration of breastfeeding and risk of asthma with an optimal duration of 4 to 6 months. A true concave relation would explain the inconsistent results from the previous studies.The question of the protective effect of breastfeeding on development of asthma has raised substantial interest, but the scientific evidence of the effects of breastfeeding is controversial [1,2]. Some epidemiologic studies provided evidence of a negative association consistent with protective effect [3-10], whereas some studies reported either no association [11-14], or a positive association between the duration of breastfeeding and the risk of asthma [15-19]. A strength of evidence indicates that short-term breastfeeding protects asthma up to 3–4 months [1,2].Gdalevich and colleagues [2] conducted a systematic review and meta-analysis of all 12 prospective cohort studies, which fulfilled pre-stated inclusion criteria. The summary OR for the effect of exclusive breastfeeding for 3 months was 0.70 (95% CI 0.60, 0.81). Friedman and Zeiger [1] summarized in their recent review that exclusive breastfeeding should be encouraged for at least 4 to 6 months. However, there is little evidence of the role of long-term breastfeeding in the development