Associations of daily air temperature with lung function and biomarkers of inflammation and oxidative stress in COPD

Rationale Greater 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. Methods We conducted a study of 166 participants with COPD (either a former or no history of smoking) from Eastern Massachusetts, USA, who completed up to four 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 x 4 km, were assigned to geocoded home addresses. We used generalized additive mixed models to investigate associations of short-term temperature exposures at 0–1, 2–6, 0–6, and 0–13-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. Results The population was 97.0% male, mean (standard deviation, SD) age = 72.8 (8.4) years, mean %-predicted forced expiratory volume in 1 second (FEV1%) (SD) = 66.2 (21.8), and mean temperature (SD) = 10.2 (10.4) °C. Higher temperatures at all moving averages were associated with lower FEV1. For example, per 5 °C increase in temperature at lags of 0–1 and 0–13 days, FEV1 decreased by (mL, 95% CI) -12.06 (-23.14; -0.98) and -16.24 (-29.23; -3.25), respectively. Similarly, higher temperatures were associated with lower forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC). 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 0–1 days and 0–13 days was associated with %-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 FVC, or other inflammatory or oxidative stress biomarkers. Conclusion Short-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.