Age-specific incidence of acute chest syndrome (ACS) and pain events classified by clinical asthma status in the infant sickle cell anemia (SCA) cohort. (A) Overall incidence rate of ACS events is higher in children with SCA and asthma (0.39 events per patient year) when compared with children with SCA and without asthma (0.20 events per patient year; P < .001). (B) Overall incidence rate of painful events is higher in children with SCA and asthma (1.39 events per patient year) when compared with children with SCA and without asthma (0.47 events per patient year, P < .001). Line segments are point-wise exact 95% confidence intervals.