Abstract

Introduction: The protective effects of breastfeeding on early life respiratory infections are established, but there have been conflicting reports on protection from asthma in late childhood. The association of breastfeeding duration and lung function was assessed in 10-year-old children.

Methods: In the Isle of Wight birth cohort (n = 1456), breastfeeding practices and duration were prospectively assessed at birth and at subsequent follow-up visits (1 and 2 years). Breastfeeding duration was categorised as “not breastfed” (n = 196); “<2 months” (n = 243); “2 to <4 months” (n = 142) and “⩾4 months” (n = 374). Lung function was measured at age 10 years (n = 1033): forced vital capacity (FVC), forced expiratory volume in 1 s (FEV₁), FEV₁/FVC ratio and peak expiratory flow (PEF). Maternal history of asthma and allergy was assessed at birth. The effect of breastfeeding on lung function was analysed using general linear models, adjusting for birth weight, sex, current height and weight, family social status cluster and maternal education.

Results: Compared with those who were not breastfed, FVC was increased by 54.0 (SE 21.1) ml (p = 0.001), FEV₁ by 39.5 (20.1) ml(p = 0.05) and PEF by 180.8 (66.1) ml/s (p = 0.006) in children who were breastfed for at least 4 months. In models for FEV₁ and PEF that adjusted for FVC, the effect of breastfeeding was retained only for PEF (p = 0.04).

Conclusions: Breastfeeding for at least 4 months enhances lung volume in children. The effect on airflow appears to be mediated by lung volume changes. Future studies need to elucidate the mechanisms that drive this phenomenon.