Associations of daily air temperature with lung function and biomarkers of inflammation and oxidative stress in chronic obstructive pulmonary disease.

rationaleGreater ambient air temperatures may have implications for respiratory health. While prior research has primarily examined the associations of air temperature with lung health in the general population, individuals with chronic obstructive pulmonary disease (COPD) may be particularly susceptible. This study aims to assess the associations between air temperature and pulmonary function, as well as biomarkers of inflammation and oxidative stress, in this potentially susceptible population.

methodsWe conducted a study of 166 participants with COPD (either a former or no history of smoking) from eastern Massachusetts, United States, who completed up to 4 visits over 12 months at the VA Boston Healthcare System between 2012 and 2017, yielding 620 observations. Daily mean temperature exposures, at a spatial resolution of 4 × 4 km, were assigned to geocoded home addresses. We used generalized additive mixed models to investigate associations of short-term temperature exposures at 0- to 1-day, 2- to 6-day, 0- to 6-day, and 0- to 13-day moving averages with repeated lung function measurements, blood biomarkers of systemic inflammation (high-sensitivity C-reactive protein [hsCRP], interleukin 6, soluble vascular cell adhesion molecule 1), and urinary biomarkers of oxidative stress (8-hydroxy-2'-deoxyguanosine, malondialdehyde), adjusting for confounders (eg, air conditioner usage and season). We performed mediation analyses to determine if temperature-lung function relationships were mediated by inflammatory or oxidative stress pathways.

resultsThe population was 97.0% male, mean (SD) age = 72.8 (8.4) years, mean (SD) percent predicted forced expiratory volume in 1 second (FEV1%) = 66.2 (21.8), and mean (SD) temperature = 10.2 °C (10.4 °C). Higher temperature exposures at all moving averages were associated with lower FEV1. For example, per 5 °C increase in temperature at lags of 0 to 1 and 0 to 13 days, FEV1 decreased by (mL, 95% CI) 12.06 (-23.14 to -0.98) and 16.24 (-29.23 to -3.25), respectively. Similarly, higher temperature exposures were associated with lower forced expiratory volume in 1 second/forced vital capacity. There were positive associations between higher temperature across all moving averages and higher hsCRP. For instance, a 5 °C increase in temperature at lags of 0 to 1 days and 0 to 13 days was associated with percent increases in hsCRP of 6.37 (95% CI, 1.05-11.97) and 9.40 (95% CI, 3.02-16.16), respectively. hsCRP did not mediate the temperature-lung function relationship. Associations were similar, adjusting for indoor and outdoor air pollution. No associations were observed with forced vital capacity or other inflammatory or oxidative stress biomarkers.

conclusionShort-term exposures to higher air temperatures were associated with lower lung function and higher hsCRP concentrations among individuals with COPD, suggesting that rising air temperature may be an important determinant of health in this susceptible group.