Chronic cough lasts more than 4 wk in children [11].
Chronic cough is associated with high morbidity in children
and their families. Postinfectious cough, protracted bacterial
bronchitis and asthma are the main causes of chronic cough in
children [23]. Chronic cough is frequent in childhood and
should be treated based on etiology. This is the first study
evaluating the relationship between serum 25(OH)D levels
and chronic cough in children. The authors propose that duration
of cough in children may be prolonged due to vitamin D
deficiency. They found that serum vitamin D levels in patients
with chronic cough were lower than those in the control
group. There was also no significant difference in serum
25(OH)D levels between RRI group and chronic cough group.