Daily smartphone voice recordings revealed subtle changes from the very first day of an asthma or COPD exacerbation, highlighting a promising new approach to remote monitoring that could one day enable earlier intervention and improve patient care.
Study: Voice as biomarker for early exacerbation detection in asthma and COPD: the TACTICAS study. Image credit: Pixel-Shot/Shutterstock.com
Asthma and chronic obstructive pulmonary disease (COPD) are chronic and distressing, often disabling, conditions, with frequent exacerbations. Being able to detect exacerbations early might allow for timely treatment, potentially improving outcomes. A recent study published in the journal ERJ Open Research found that voice changes can occur as early as the first day of an exacerbation, supporting the future use of voice analysis for remote monitoring and earlier treatment.
Voice analysis offers a new monitoring approach for asthma and COPD
Asthma and COPD exacerbations are episodes in which symptoms suddenly worsen, often leading to poorer quality of life, increased medication use, hospitalization, and a greater risk of death. Because early treatment is associated with better outcomes, finding reliable ways to detect these flare-ups as soon as they begin has become an important goal in managing both conditions.
Current approaches to remote monitoring rely on measures such as lung function tests, blood samples, or vital signs, but these can be invasive, labor-intensive, or require specialist equipment. Researchers have therefore turned their attention to digital voice biomarkers, as changes in the airways during an exacerbation can alter the way a person speaks. Although voice analysis has shown promise in detecting a range of other health conditions, its potential for monitoring asthma and COPD exacerbations remains largely unexplored.
Patients recorded speech throughout three-month monitoring period
The current study aimed to understand how voice changes could reflect exacerbations of these two conditions, using specific voice features as biomarkers of exacerbation onset, and of the different types of exacerbation symptoms. They also explored how well participants would follow the voice-based app for daily monitoring.
The researchers conducted a prospective cohort study (the TACTICAS (Telemonitoring for Asthma and COPD Through voICe AnalysiS) study), including 73 participants recruited at respiratory clinics. Of these, 35 had asthma, and 38 had COPD, with a mean age of 62 years.
The participants recorded their own voice three times a day for three months using their own mobile phones. The app prompted speech recordings in the morning, after a light exercise task in the afternoon, and again in the evening alongside symptom questionnaires. They used the TACTICAS app, co-created with asthma and COPD patients and designed for home use.
The voice capture included a sustained vowel sound and either a paragraph reading or an answer to a question. The participants also used the validated EXACT questionnaire to detect exacerbations, either by an increase in symptom score by over nine points from the baseline for three days, or scoring over 12 points for two consecutive days.
Additionally, the researchers checked in with the participants every four weeks, and data on medication or symptom increase were stored in the electronic Case Record Form (eCRF).
The exacerbations were clinically verified using electronic health records (EHR) in combination with medication use and patient-reported symptoms, and only validated events were included in the analysis. Events that were not reported but picked up by eCRF or EHR analysis were included as well.
The researchers obtained 23,799 recordings in total, of which 2,737 occurred during exacerbations. Of these, 227 were on the day of onset, recovery, or peak. Within the study period, they captured 38 exacerbations, mostly mild and moderate. Most were captured by the questionnaire.
Voice changes emerged from the very start of exacerbations
The analysis showed that measurable changes in speech were already present on the first day of an exacerbation. The multilevel analysis identified 13 acoustic speech features that changed significantly at onset, including lower median pitch, shorter sustained vowel sounds, and greater shimmer, an indicator of irregular vocal-fold vibrations. The Noise-to-Harmonics Ratio also increased, suggesting an overall decline in voice quality.
Rather than occurring only at the start of an episode, these changes evolved throughout the exacerbation. By collecting daily voice recordings, the researchers were able to track how speech changed from the onset through peak symptoms to recovery, providing a detailed picture of the progression of an exacerbation.
The study also found that different voice features appeared to reflect different symptom patterns. Shimmer and the Noise-to-Harmonics Ratio were more strongly associated with chest symptoms, potentially because increased airway obstruction reduces airflow during speech, while minimum pitch showed a stronger relationship with breathlessness. The authors caution that these findings are exploratory and require confirmation in larger studies.
Interestingly, the voice changes were similar in participants with asthma and those with COPD. The researchers suggest this may indicate that the underlying physiological changes occurring during an exacerbation, rather than the specific diagnosis, are driving the alterations in speech. These changes may result from a combination of increased airway obstruction, sputum impaction, inflammation of the vocal folds, and changes affecting the larynx. However, they also emphasize that the study was not large enough to determine this with certainty.
The authors propose that these changes arise from worsening airway obstruction during an exacerbation, which places mechanical strain on both the respiratory system and the structures involved in speech production. As airway resistance increases, the respiratory muscles work harder, lung expansion becomes more limited, and the pressure beneath the vocal folds falls.
This can make it more difficult to maintain a steady voice, shorten speech duration due to reduced airflow, and produce a breathier voice with increased shimmer. As participants recovered, maximum voice pitch increased, which the researchers suggest may reflect the restoration of more normal speech mechanics.
The study also highlights a practical advantage of voice monitoring. Participants were less likely to complete symptom questionnaires when they felt unwell, potentially preventing the questionnaire-based detection of exacerbations. In contrast, recording a short voice sample may offer a simpler, less burdensome way to monitor respiratory health, making it a potentially inexpensive and unobtrusive tool for future home-based monitoring.
Although the findings are promising, the authors stress that larger validation studies and predictive models will be needed before voice-based biomarkers can be incorporated into routine clinical care.
Observational study identifies opportunities for future research
To improve confidence that each flare-up represented a genuine exacerbation, the researchers verified events using multiple sources, including symptom questionnaires, electronic health records, medication use, and clinical review. However, they did not use the Rome criteria, a more recent framework for defining COPD exacerbations that incorporates physiological measurements such as heart rate, breathing rate, oxygen saturation, and inflammatory markers alongside symptoms.
Since the study did not collect these vital signs, the authors note that some exacerbations may have been classified differently under the Rome definition. They also point out that heart rate itself may influence voice characteristics, making it an important factor to consider in future studies.
Also, the findings remain observational and show associations rather than prediction. While voice changed alongside exacerbations, the study cannot determine whether these changes can reliably predict an impending flare-up. This distinction is particularly important because many other acute illnesses, including heart failure and common respiratory infections, can also affect the voice.
Several additional limitations should also be considered. The researchers did not systematically record participants' daily inhaler use, even though inhaled corticosteroids can alter voice quality. The study was also relatively small and included only native Dutch speakers, limiting the extent to which the findings can be applied. In addition, the large number of statistical comparisons increased the likelihood that some significant associations were due to chance.
Future studies should validate these findings in larger, multilingual populations and further refine the predictive algorithms already under development. If voice-based prediction proves feasible, the authors suggest it could eventually support care pathways by prompting additional diagnostic testing when early signs of an exacerbation are detected.
Smartphone speech analysis could support future respiratory care
Taken together, the study indicates that measurable voice changes occur from the very onset of an asthma or COPD exacerbation.
These results substantiate the potential of voice as biomarker for detection of exacerbations in chronic respiratory diseases and illustrate the usefulness of home monitoring with a mobile phone.
However, the authors emphasize that larger validation studies and predictive models are needed before voice-based biomarkers can be used clinically for remote exacerbation detection.
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