The levels of fractional exhaled nitric oxide, a marker of eosinophilic airway inflammation, were higher in adolescents after rain, snow or hail, according to a study presented at the recently concluded ATS 2022, the conference of the American Thoracic Society.1 This effect was particularly seen in asthmatic adolescents.

To examine the association of precipitation (rain, snow, hail) in the preceding days with pulmonary function and airway inflammation, researchers enrolled 972 adolescents with an average age of 13 years. About 50% of the participants were female and 13% had asthma. Data was obtained from the ongoing Project Viva, a research study analyzing impact of maternal diet on the health of their children, initiated in 1999. Their residential places were correlated with weather data (daily precipitation in mm) over the previous week. The forced expiratory volume in one second (FEV1), forced vital capacity (FVC) and fractional exhaled nitric oxide (FeNO) were regularly measured and their association with 1-, 2-, 3-, and 7-day moving averages of precipitation in the last week was assessed. The mean FeNO level was 25.9 ppb.

Over the previous 7 days, the daily precipitation was 1.96 mm (median). A link between the 2-, 3-, and 7-day moving averages of daily precipitation and higher FeNO was noted. For every 2 mm daily rise in the 7-day moving average for daily precipitation, the FeNO increased by 3.64%. This increase in FeNO was 8.55% in adolescents with asthma. This association remained unchanged after adjusting for exposure to pollutants (ground level ozone and small particulate matter). The rise in FeNO was evident at daily averages of less than 5 mm. No such association was noted for FEV1 or FVC.

An inverted U-shaped relationship was observed between recent average precipitation and FeNO in the additive regression model. The maximum impact was at around 12mm. As the precipitation increased, this association was seen to reduce.

Stormy weather has been known to trigger and aggravate respiratory symptoms in earlier studies. This study has added to the growing evidence regarding the impact of climate change on human health.  Exposure to precipitation even for a short duration was associated with higher FeNO levels especially in adolescents with asthma indicative of allergic airway inflammation triggered by  precipitation in the past week. Growth of molds may also be a contributory factor. As a risk factor, precipitation is rare and also non modifiable. But it does highlight the need to be prepared for such weather conditions to preempt increase in symptoms and/or acute exacerbations.

Reference

1. Nassikas N, et al. Short-term exposure to precipitation and respiratory health in adolescents. American Thoracic Society (ATS) 2022; Poster 209. May 18, 2022.