That's what Julie Marchant, MBBS, and colleagues report in the journal Chest. Marchant works at the Royal Children's Hospital in Brisbane, Australia.
For adults, the most common causes of chronic cough are asthma, gastroesophageal reflux disease (GERD), and upper airway cough syndrome (related to postnasal drip), according to background information in Marchant's study.
Marchant's team studied 108 young children (average age: 2.6 years) with chronic cough who were seen at Brisbane's Royal Children's Hospital between June 2002 and June 2004.
The researchers wanted to find out what was causing the kids' chronic cough.
Children's Chronic Cough
The study was open to all kids aged 18 and younger (excluding premature babies) treated at the hospital for chronic cough.
Chronic cough was defined as cough lasting for more than three weeks.
Of the 114 kids who were invited to participate, 108 took part. Their coughing had lasted for six months, on average. Most -- 89% -- had "wet" coughs.
The researchers noted the kids' medical history and exposure to smoke. They also gave kids a thorough physical exam.
Tests included flexible bronchoscopy, in which doctors used a tiny scope to view and test samples of fluid from patients' airways while patients were under general anesthesia. In another test, the researchers examined the kids' mucus (sputum).
The researchers aren't recommending those tests for every kid with chronic cough. They used the tests for the study's sake.
The kids got medication as needed. They were followed until their coughs ended or a year passed, whichever came first. Kids' symptoms were recorded in cough diaries.
Leading Cause: Bronchitis
Bacterial bronchitis was the main cause of kids' chronic cough, the study shows.
Based on the findings, Marchant and colleagues write that chronic cough has different causes in kids and adults, and that it may be "unsuitable" to approach kids' chronic cough like adults' chronic cough.
Few participants were over 10 years old, so it's not clear if the results apply to older children, the researchers note.