Only 2 of the 5 included studies investigated regular continuous montelukast (n = 1691) [4, 18]. The pooled estimate comparing the number of wheezing episodes was not statistically significant (MD = −0.40, 95% CI −1.00 to 0.19, mean for montelukast 2.05 vs placebo 2.37 (p = 0.18)); analysis showed that there was a substantial heterogeneity between the included studies (Fig. 4a, p = 0.04, I 2 statistic = 77%).Fig. 4Continuous montelukast vs placebo. a Number of wheezing episodes. b Unscheduled medical attendances . c Number of oral corticosteroid courses 