Influence of Gaseous Pollutants on COPD Exacerbations in Patients with Cardiovascular Comorbidities

Exacerbations of chronic obstructive pulmonary disease (COPD) are a serious public health issue. Ambient pollution and meteorological factors are considered among precipitating factors. There are few data concerning the impact of ambient pollutants other than particulates on COPD exacerbations. Among gaseous pollutants four main groups of substances are primarily monitored: nitrogen oxides (NOx), sulphur dioxide (SO₂), carbon monoxide (CO), and ozone (O₃). In this study, 12,889 hospitalizations in the years 2006-2014 due to exacerbations of COPD in patients having a co-existing cardiovascular pathology were retrospectively analyzed. Cardiovascular disease was ruled out as the underlying reason of hospitalization. Data concerning the then accompanying gaseous pollutants and weather conditions were collected. The findings were that the impact of SO₂ content was significantly associated with the relative risk (RR) of COPD exacerbation when the exposure took place at least 30 days or longer before hospital admission (RR 1.04-1.05; p < 0.05). In contrast, risk of COPD exacerbation rose when a shortening of the time lag between exposure to NOx and hospital admission was considered (RR 1.02-1.04; p < 0.05). O₃ exposure was associated with a lower risk irrespective of the length of exposure/exacerbation lag (RR 0.77-0.90; p < 0.05). There were insignificant associations observed for CO. In conclusion, the study demonstrates a salient influence of a co-existing cardiovascular malady on the appearance of COPD-related respiratory exacerbations when the pollutant SO₂ and NOx contents rose. In contrast, higher O₃ content was associated with a lower risk of COPD exacerbation.