- D3.512 - Objective Ambulatory Assessment of Indoor Air Quality and Cough Frequency

Although patients frequently report environmental factors as triggers for cough, real-world evidence linking specific indoor air quality (IAQ) parameters to objectively measured cough events remain limited. Elucidating these associations is essential for developing targeted air quality management strategies. This study aimed to evaluate the relationship between IAQ parameters and cough frequency in daily life using simultaneous, objective monitoring of environmental conditions and cough events.

We enrolled patients with cough from two university hospitals in Korea. IAQ parameters—including temperature, relative humidity, PM₂.₅, PM₁₀, CO₂, and VOC/NOx indices—along with ambient sound were continuously monitored in participants’ daily environments (one or two locations per participant) for a minimum of 7 days using a commercially available device (LG Electronics). Objective cough frequency was quantified from audio recordings using the Coughy AI algorithm. Baseline cough hypersensitivity questionnaire (CHQ) data were collected. IAQ levels were categorized according to provider-defined criteria. Spearman correlation analyses were performed to assess associations between IAQ indices and cough frequency during periods with recorded cough events (frequency > 0).

A total of 37 patients were enrolled; 28 females and 9 males with median age 41 years [range, 20–61]. Overall IAQ conditions were generally favorable; however, more than 10% of CO₂ and VOC index measurements were classified as “Polluted,” while the NOx index consistently remained within the “Good” range. Common CHQ-reported triggers (n = 29) included cold air (72.4%), dry air (79.3%), perfumes or scents (51.7%), and smoke or smoky environments (62.1%). No significant correlations were observed between overall IAQ indices and cough frequency. However, analyses restricted to daytime data suggested potential associations in specific subgroups. Among participants exposed to lower temperatures (<20°C, n = 17), relative humidity demonstrated a weak negative correlation with cough frequency (Spearman’s ρ = −0.27, p < 0.001). Additionally, in participants experiencing “Very Polluted” VOC index levels (n = 20), the VOC index showed a weak positive correlation with cough frequency (Spearman’s ρ = 0.20, p < 0.001). One participant exhibiting the greatest IAQ variability and reporting cold air and smoke as triggers demonstrated moderate positive correlations between cough frequency and particulate matter concentrations (PM₂.₅ and PM₁₀; Spearman’s ρ = 0.58, p < 0.001).

This study successfully captured real-world IAQ variability and objectively measured cough events in patients with cough using a novel ambulatory monitoring approach. The predominantly favorable IAQ conditions limited the ability to assess trends across lower or more polluted exposure levels; nonetheless, potential associations were observed under specific environmental circumstances. These findings demonstrate the feasibility of objective, real-world monitoring of IAQ and cough and underscore the need for further studies incorporating broader environmental exposure ranges to better delineate the impact of IAQ on cough frequency.