A randomized controlled trial investigating the effect of thermal steam spray on nasal condition, neurological function, and sleep quality in young adults with nasal congestion and irregular sleep patterns

Background Intranasal thermal steam spray (ITSS) has been suggested to relieve nasal stuffiness and improve sleep-related symptoms. However, its effects on respiratory capacity, neurological functions, including autonomic nervous system (ANS) and brain activities, remain underexplored. Therefore, this study aimed to investigate the effects of an ITSS intervention on nasal condition, respiratory and neurological functions, and sleep quality in young adults with nasal congestion and irregular sleep patterns. Methods Sixty university students (aged 20–26 years) with an average duration of nasal congestion and sleep irregularity of over three years participated. Two dormitories were randomly assigned to either a control group (CON; n = 30) or an intervention group (ITSS; n = 30). The ITSS device, delivering 43°C thermal wet steam using jet stream technology, was administered for 15 min, 3 times per week, 30 min before bedtime for 8 weeks. Results After the intervention, subjective nasal congestion and sleep conditions deteriorated in the CON but improved in the ITSS ( p < 0.001). Pulmonary outcomes, including reduced respiratory rate ( p < 0.001) and increased FEV₁ ( p < 0.001) and PEF ( p < 0.001), improved only in the ITSS. Heart rate variability and blood pressure indices also showed favourable changes. EEG analysis revealed increased wide band, alpha, and gamma powers in the ITSS, contrasting with declines in the CON ( p < 0.05). In the ITSS group, PSQI-K components improved, with daytime dysfunction reduced by 32.78 ± 41.40% ( p < 0.001). Total PSQI-K scores rose in the CON group (+14.64 ± 22.44%) but declined in the ITSS group (−38.90 ± 21.99%), showing a significant difference ( p < 0.0001). Conclusions These findings suggest that ITSS enhances airflow by humidifying the nasal environment, thereby facilitating respiratory function and stabilizing ANS activity and brain function. This process ultimately contributes to improved overall sleep quality in young adults experiencing nasal congestion and irregular sleep patterns. Trial registration The study was retrospectively registered on April 3, 2025, in the Clinical Research Information Service (https://cris.nih.go.kr/cris/search/listDetail.do/) under registration number KCT0010381.