Social Distancing in Relation to Severe Exacerbations of Chronic Obstructive Pulmonary Disease: A Nationwide Semi-Experimental Study During the COVID-19 Pandemic

Social distancing measures introduced on March 12, 2020, in Denmark during the COVID-19 pandemic may affect non-COVID-19 admissions for severe acute exacerbation of chronic obstructive pulmonary disease (s-AECOPD). We compared rates of s-AECOPD in a nationwide, observational, semi-experimental cohort study using data from all Danish inhabitants between calendar week 1 through 25 in 2019 and 2020. In a sub-cohort of patients with chronic obstructive pulmonary disease, we examined incidence of s-AECOPD, admissions to an intensive care unit, and all-cause mortality. A total of 3.0 million inhabitants aged >= 40 years, corresponding to 3.0 million person-years, were followed for s-AECOPD. In the social distancing period in 2020, there were 6,212 incidents of s-AECOPD, compared with 11,260 incidents in 2019, resulting in a 45% relative risk reduction. In the cohort with chronic obstructive pulmonary disease (n = 16,675), we observed a lower risk of s-AECOPD in the social distancing period (subdistribution hazard ratio (HR) = 0.34, 95% confidence interval (CI): 0.33, 0.36; absolute risk: 25.4% in 2020 and 42.8% in 2019). The risk of admissions to an intensive care unit was reduced (subdistribution HR = 0.64, 95% CI: 0.47, 0.87), as was all-cause mortality (HR = 0.83, 95% CI: 0.76, 0.90). Overall, the social distancing period was associated with a significant risk reduction for hospital admittance with s-AECOPD.