For adults with COPD, physical activity is strongly recommended, according to Mary B. Rice, MD, MPH. However,
it is unknown whether physical activity affects daily exposure to air pollution or reduces or aggravates the
effects of pollution on the lungs.
For a study published in Chronic Obstructive Pulmonary Diseases, Dr. Rice and colleagues tracked former smokers with
moderate to severe COPD for 4 non-consecutive months throughout different seasons. Participants had
a 10 pack-year or more smoking history, with no active smoking for at least 6 months before study enrollment, lived
in an urban environment (within 50 km of the Harvard University air pollution supersite), and had a clinical
diagnosis of COPD with at least moderate airflow obstruction, defined as (FEV1)/FVC ratio of less than 0.70 and FEV1
less than 80% predicted, using NHANES III prediction equations. Patients with a history of interstitial
lung diseases, lung cancer, or bronchiectasis were excluded from the study.
Adjusting for Demographics, Seasonal Covariates
The researchers evaluated par- ticipants’ daily lung function FEV1 and FVC, step count, and
exposure to pollutants (ozone [O3], fine particulate matter [PM2.5], and nitrogen dioxide [NO2]) measured by
portable air quality monitors. Multilevel linear mixed-effects models were created with random intercepts for person and
person-observation month. These models were adjusted for demographic/seasonal covariates to test
whether step count correlated with daily pollution exposure, and whether links between lung
function and prior-day pollution differed based on prior- day step count.
Dr. Rice and the study team noted that higher same-day personal exposure to PM2.5 and O3 were
linked with higher daily step count, but not NO2. “Each interquartile range (IQR) increment in step
count was correlated with 0.97 µg/m3 (95% CI, 0.30- 1.64) higher exposure to PM2.5 and 0.15 ppb
(95% CI, -0.05 to 0.35) higher exposure to O3 in adjusted models,” the study authors wrote. “We
observed an interaction between prior-day NO2 and step count on FEV1 and FVC (Pinteraction<0.05) in
which the negative associations between NO2 and lung function were reduced or absent at higher
levels of daily activity.” For example, they noted, in the lowest tertile of step count, FEV1 was
28.5 mL (95% CI, -41.0 to -15.9) lower per IQR of NO2, but there was no correlation in the highest
tertile of step count (-1.6 mL;
95% CI, -18.4 to 15.2).
No Evidence to Suggest Avoiding Physical Activity
Additionally, the study team assessed links of previous-day NO2 exposure and lung function within
tertiles of prior-day total step count. “The negative associations between NO2 and lung function
were greatest in magnitude on participant days with the lowest level of physical activity and
absent on participant days with the highest activity levels (Figure),” the study authors observed.
“In this study of former smokers with COPD living in an urban environment, routine physical
activity resulted in only a modest difference in pollution exposure compared with sedentary
behavior,” Dr. Rice and colleagues wrote. “Further, physical activity attenuated the negative
association between personal exposure to NO2 and lung function in COPD. [We] did not find evidence
to suggest that [patients with COPD] should forego physical activity […] to avoid pollution
exposure at typical daily exposure levels within current [Environmental Protection Agency] standards.”
