in adults with chronic obstructive pulmonary disease (COPD) based on data from 117 individuals.
COPD is attributed to environmental factors including air pollution, and air pollution has been linked to increased risk of hospitalization and mortality because of acute COPD exacerbation, wrote Huan Minh Tran, PhD, of Taipei (Taiwan) Medical University and colleagues. However, the effects of air pollution on climate-associated health outcomes in COPD have not been explored, they said.
In a study published in Science of The Total Environment the researchers identified 117 adult COPD patients at a single center in Taiwan. They measured lung function, 6-minute walking distance, oxygen desaturation, white blood cell count, and percent emphysema (defined as low attenuation area [LAA]) and linked them to 0- to 1-year, 0- to 3-year, and 0- to 5-year lags in exposures to relative humidity (RH), temperature, and air pollution. The mean age of the participants was 72.9 years; 93% were men.
Pollution was defined in terms of fine particulate matter (PM2.5).
Overall, an increase in RH by 1% was associated with increases in forced expiratory volume in 1 second (FEV1), eosinophils, and lymphocytes.
A 1% increase in RH also was associated with a decrease in the total-lobe LAA.
As for temperature, an increase of 1° C was associated with decreased oxygen desaturation and with decreases in right-, left-, and upper-lobe LAA values.
When the researchers examined the impact of pollution, they found that a 1 mcg/m3 increase in PM2.5 was associated with a decrease in the FEV1 as well as with an increase in oxygen desaturation. A 1 mcg/m3 increase in PM10 and PM2.5 was associated with increases in the total-, right-, left, and upper-lobe LAA; increases in lower-lobe LAA were associated with an increase in PM2.5 only.
“This is reasonable because PM2.5 can travel and deposit in distal parts of the lung, while PM10 is preferably deposited in the larger airways of the upper lung regions,” the researchers wrote in their discussion.
A one part per billion increase in nitrogen dioxide (NO2) was associated with decreased FEV1 and increased upper-lobe LAA.
“We observed that NO2 fully mediated the association between RH and FEV1, while PM2.5 fully mediated associations of temperature with oxygen saturation and emphysema severity in COPD patients,” the researchers added.
The study findings were limited by several factors including the relatively small and homogeneous male, Taiwanese population, which may limit generalizability, the researchers noted. Other limitations included the lack of control for factors such as body mass index, occupational exposure, comorbidities, medication use, and indoor air pollution, they said.
However, the results suggest that air pollution could have an effect on the established associations between climate and adverse health outcomes in COPD, and more research is needed. Climate change–related air pollution is an important public health issue, especially with regards to respiratory disease,” they concluded.
The study was supported by the Ministry of Science and Technology of Taiwan. The researchers had no financial conflicts to disclose.