Seasonality, ambient temperatures and hospitalizations for acute exacerbation of COPD: a population-based study in a metropolitan area

Almagro, Pere; Hernandez, Carme; Martinez-Cambor, Pable; Tresserras, Ricard; Escarrabill, Joan

The observed mortality during hospitalization was 3.2%, being higher in the summer months (P=0.050). The most frequent comorbidities recorded were hypertension (43.6%), psychiatric disorders including anxiety and/or depression (42.0%), heart failure (32.8%), ischemic heart disease (28.3%), and diabetes mellitus (28.0%). The total number of comorbidities was lower during the winter months than in the rest of the year (P0.001), although no difference was seen in the Deyo-Charlson Index (Table 1) . The mean annual maximum temperature was 19.7°C± 6.6°C with a maximum of 34.5°C, while the mean of the minimum temperatures was 8.5°C±5.7°C with a minimum of 0.0°C. The values of the mean daily temperatures ranged between 3.8°C and 27°C, with a mean value of 13.7°C± 6.2°C and an interquartile range (25%-75%) between 9.6°C and 19.2°C. The maximum, minimum, and mean temperatures were closely and similarly related with the number of hospitalizations ( Figure 2 ). On average, in an unadjusted model we found that for each Celsius degree decrease in mean weekly temperature, hospital admissions increased by 5.04% (r 2 =0.591, P0.001, see Figures 3 and 4).