Postnasal Drip Linked With More Nighttime Coughing in Children With Allergic Asthma

The total number of overnight coughs was significantly higher in children with allergic asthma with postnasal drip (PND) than in children with atopic asthma without PND, according to the results of a recent study published in The Tokai Journal of Experimental and Clinical Medicine.

However, results also showed that the overnight cough pattern was similar for both patients with and without PND.

Researchers aimed to investigate the relationship between PND and cough in children with allergic asthma and allergic rhinitis. PND is associated with diseases known to cause chronic cough, but it remains unclear whether PND itself causes cough and, if PND does cause cough, how it does so.

This study involved pediatric inpatients at Tokai University Hospital and Tokai University Hachioji Hospital in Japan from September 2010 to December 2015. Researchers compared 2 groups: 8 children with atopic asthma with PND and 27 children with atopic asthma without PND. The mean age of the group of patients with atopic asthma with PND was 8 years and 4 out of the 8 patients were female. All patients in both groups had allergic rhinitis and data was collected during an acute exacerbation of asthma for the patients.

Researchers used their own cough monitoring system in order to count the number of coughs and determine cough patterns for each patient at night. The cough monitoring system consisted of a high-resolution microphone, a highly sensitive accelerometer, and a recorder. The microphone was placed at the second intercostal space in the mid-clavicular line and the accelerometer was placed in the center of the abdomen. Data was collected in 8-hour nightly sessions from 10:00pm to 6:00am.

Patients with allergic asthma with PND had significantly more overnight coughs than patients with atopic asthma without PND. The total number of overnight coughs for patients with PND was 137.5 (36.2) per night while the total number of overnight coughs for patients without PND was 99.8 (47.2) per night.

To determine cough patterns, researchers calculated the number of coughs every 30 minutes. Patients with PND coughed more frequently than patients without PND at all points during the night. However, cough patterns of patients with and without PND were similar in that cough counts increased at sleep onset and again in the early morning.

Limitations of this study include the relatively small sample size. Researchers also analyzed hospitalized children, so results may not be applicable for children with asthma in a stable state.

For patients with PND, upper airway secretions and allergic inflammation in the airway mucosa may have been the reason for the frequent coughing and cough pattern observed in patients with PND, the researchers noted. The researchers added that the similar cough pattern found in patients with and without PND suggests that the pattern is due to allergy inflammation of the upper and lower airways.

Reference

Hirai K, Kaiga C, Otomo T, Kuruma K, Kama Y, Yamaguchi K, Kato M, Mochizuki H. Effect of post-nasal drip on overnight-cough frequency and cough pattern in children with asthma. Tokai J Exp Clin Med. 2022;47(2):79-84.