Combined exposure to birch pollen and thunderstorms affects respiratory
health in Stockholm, Sweden
Abstract
Background: Thunderstorm asthma is a term used to describe surges
in acute respiratory illnesses following a thunderstorm and is often
attributed to an intense exposure to aeroallergens. Several episodes of
epidemic thunderstorm asthma have been observed worldwide; however, no
such cases have been described in Sweden. In Sweden, the most prominent
exposure to air-borne pollen occurs during the blooming of the birch. We
aimed to explore the potential associations between the respiratory
health and the combined exposure to thunderstorms and birch pollen.
Methods: We investigated the association between the daily
numbers of outpatient visits due to respiratory cases and the combined
exposure to thunderstorms and birch pollen during a period of May 1
st - August 31 st in 2001-2017, in
Stockholm County, Sweden, by using time series analysis with log linear
models. Results: We detected a significant increase in the number
of outpatient visits on both the same day and the day after the
occurrence of a thunderstorm, when either the concentrations of ambient
birch pollen or the number of thunderstorm-associated lighting
discharges were within the highest categories. Conclusions: It is
possible that co-exposure to heavy thunderstorms and high concentrations
of birch pollen affects the respiratory health of the Stockholm
population. To the best of our knowledge, this is the first study
addressing the thunderstorm-related respiratory illnesses in Sweden and
the effect of birch pollen. Other similar studies are needed before any
conclusions can be drawn; however, our study may be important for future
public health advice related to thunderstorm asthma.