A pilot study on the relationship between temperature and humidity and the detection of basidiomycetes in sputum from patients with chronic cough in the Nagasaki region.

BACKGROUND

Environmental fungi, particularly basidiomycetes, have been proposed to contribute to fungus-associated chronic cough (FACC), but the association remains incompletely substantiated and may vary by region and season. Therefore, we performed fungal cultures of spontaneous sputum from patients with unexplained or refractory chronic cough (UCC/RCC) in the Nagasaki region and investigated associations between basidiomycete detection and monthly temperature and humidity.

METHODS

Thirty patients with UCC/RCC and 30 patients with other respiratory diseases without chronic cough (CC) underwent spontaneous sputum collection and fungal culture. Participants completed a cough/sputum symptom questionnaire [cough visual analog scale (VAS) and chronic obstructive pulmonary disease (COPD) Assessment Test (CAT) questions 1-2], underwent chest computed tomography, and were assessed for comorbidities and medications. We compared (I) CC vs. non-chronic cough (NC) groups and (II) basidiomycete-positive vs. basidiomycete-negative patients within the CC group.

RESULTS

Basidiomycetes were detected in sputum samples from 9 of 30 patients (30.0%) in the CC group, whereas none were detected in the NC group (P=0.002). Basidiomycetes were primarily detected in samples collected between June and August and the monthly detection rate showed a significant correlation with monthly humidity and temperature. Within the CC group, no significant differences were observed between basidiomycete-positive and -negative patients regarding demographics, smoking history, underlying diseases, medication use, symptom scores, or high-resolution computed tomography (HRCT) findings.

CONCLUSIONS

In the Nagasaki region, basidiomycete-positive sputum cultures were significantly more frequent in patients with CC than in patients without CC. A basidiomycete species profile different from previously reported profiles was observed, and detection frequency showed seasonal correlation with temperature and humidity in this cohort. These findings suggest the importance of proactively performing fungal cultures while considering regional and seasonal factors when evaluating possible FACC.