Seasonal dynamics of COPD exacerbation and outdoor environmental
factors
We noted seasonal changes in CE that differed by age group (Figure 1B).
COPD exacerbation was predominantly in winter and less frequent in
summer, and this tendency was particularly severe in those aged 60 or
older.
There were definite seasonal variations in NO2, PM10,
SO2, WS and SS (Figure 1C). Contaminants such as
NO2, PM10, and SO2 mainly showed a
cyclic seasonal pattern with highs in winter and lows in summer.
Environmental factors such as WS and SS also showed cyclic patterns with
highs in late winter and early spring and lows in the autumn. Table 2
shows the median values for the air pollutants and environmental
factors. We used these median values when calculating the risk ratio
(RR).