Active smoking and a past myocardial infarction status induce more vulnerability to urban heat stress in COPD

Introduction: Chronic obstructive pulmonary disease (COPD) is a highly prevalent disorder and a leading cause for morbidity and mortality worldwide. While several studies have shown an increased risk of exacerbation during cold winter months, heat-related exacerbations are less well studied. Aims and Objectives: With climate change scenarios predicting a higher frequency and duration of heat waves, we aimed to identify patient groups most at risk for heat-related exacerbations. It was our goal to determine at which temperature threshold daily hospital admissions due to acute exacerbations of COPD (AECOPD) increase during the summer in Berlin. Methods: We analyzed retrospective demographic and medical data from 1, 191 patients, who were hospitalized for AECOPD in the metropolitan area of Berlin, Germany. Climate data were available from the Deutscher Wetterdienst. Results: Patients with COPD exacerbations during hot summer periods had more often a history of myocardial infarction (P = 0.014). An AECOPD during colder summers happened to patients with a higher Charlson index, who suffered in increased numbers of peripheral vascular diseases (P = 0.016) or tumors (P = 0.004). In hot summers, more active smokers developed an AECOPD than former smokers (P = 0.011). A Poisson regression analysis revealed an increase of hospital admissions per day if the daily minimum temperature increased above 18.3°C (P = 0.006). Conclusions: Our results indicate that active smoking and a past myocardial infarction status induce more vulnerability to urban heat stress in COPD. If minimum outdoor temperatures in Berlin increase above 18.3°C, COPD patients should consider heat protection to prevent heat stress.