An increase in night-time coughing, measured using a smartphone app, may be a sign of worsening asthma, according to new research.

"Until now, we haven't had a reliable tool for measuring peoples' asthma symptoms overnight, so we know very little about night-time coughing and what it means," Dr. Frank Rassouli of Cantonal Hospital St. Gallen, in Switzerland, said in a statement from the 2020 virtual meeting of the European Respiratory Society, where the findings were presented on August 25.

"Our results show that night-time coughing has potential as a marker of asthma worsening. Clinically, this is plausible because increase in cough is one cardinal symptom of asthma deterioration," Dr. Rassouli added in an email to Reuters Health.

The study involved 94 patients with asthma. For 29 days, the patients slept with the cough-detecting smartphone app running in their bedroom. The app also prompted patients to report their night-time symptoms. Asthma symptoms were evaluated in the clinic on the first and last day of the study.

The researchers observed a strong and significant correlation between an increase in night-time cough over the course of one week and a subsequent worsening of asthma symptoms. An increase of 100 coughs per week was associated with a decrease of 0.56 points in the Asthma Control Test (ACT) for that week and a decrease of 0.25 points in ACT the following week, they report in their conference abstract.

"Our results suggest that night-time coughing can be measured fairly simply with a smartphone app and that an increase in coughing at night is an indicator that asthma is deteriorating. Monitoring asthma is really important because if we can spot early signs that it's getting worse, we can adjust medication to prevent asthma attacks," Dr. Rassouli said in the statement.

There was "very good cooperation" from the patients, he told Reuters Health, with the caveat that "we always work with a selected subgroup of patients" who are especially interested in technical interventions.

The next step, Dr. Rassouli said, is to develop an intervention mode to transfer the prediction model into clinical practice, with the goal of making the app available to clinicians and patients.

His team has also started a study investigating the app to gauge night-time cough as it relates to worsening of chronic obstructive pulmonary disease (COPD).

Commenting on the study in the statement, European Respiratory Society President Dr. Thierry Troosters of KU Leuven, in Belgium, said, "This study offers a potential new way to monitor patients for signs that their asthma might be getting worse, and the fact that it works via a smartphone makes it accessible to most patients."

"The app could also make it easier to gather lots of data to study night-time coughing in asthma and other respiratory conditions. The elegant mix of easy and available hardware such as a smartphone, combined with artificial intelligence that can work with 'noisy' data, will provide clinicians with additional eyes and ears to judge the clinical condition of their patients in real life, rather than only at the doctors' office," Dr. Troosters added.

The study was funded by CSS Health Insurance, in Lucerne, Switzerland. The authors report no conflicts of interest.