Recurrent wheezing and asthma-Epidemiology and environmental determinants.

Wheeze is the musical continuous sound produced by oscillations in any critically narrowed airways, and heard mostly on expiration. It is common in preschool age, about half of all children will experience an episode of wheezing by their sixth birthday. Asthma is usually characterized by cough, wheeze, chest tightness and fast breathing. It is a significant global health issue and affects both children and adults. The prevalence is on the increase, especially in LMIC. Studies from different populations have revealed the key role influencing the progression from preschool wheezing to childhood asthma. Recurrent wheezing is four or more episodes in the preceding year and has a spectrum of phenotypes and with heterogeneous features. Phenotypes of wheezing were proposed to facilitate the identification of young children who are at risk of subsequent development of asthma. The epidemiology and environmental determinants of recurrent wheezing and asthma are discussed.