Higher levels of pollen were significantly associated with reduced lung function in adults with chronic obstructive pulmonary disease (COPD), based on data from more than 1800 lung tests taken during pollen season.

Previous studies, notably the SPACE study, have shown associations between exposure to air pollutants and lower forced expiratory volume in 1 second (FEV₁), worse respiratory symptoms, and increased use of healthcare among individuals with COPD, said Mary B. Rice, MD, MPH, Mark and Catherine Winkler Associate Professor of Environmental Respiratory Health at the Harvard T.H. Chan School of Public Health in Boston.

However, climate change is extending the length of pollen seasons, and increasing the concentration of pollen in the air, Rice noted. The effects of aeroallergens in general, and ambient pollen in particular, on respiratory health in a population more sensitive to air quality have not been well studied, she said.

In a new study published in Chronic Obstructive Pulmonary Diseases, the researchers reviewed data from 1808 at-home lung tests for 30 adults with moderate-to-severe COPD living in Boston, during pollen season. Participants completed four clinic visits over a 1-year period and performed daily spirometry during four 30-day periods in seasons of high pollen. The mean age of the participants was 71.11 years, 43.3% were men, and ambient total pollen was based on regional measurements.

Overall, lung function declined significantly at 3 days following a high level of ambient pollen exposure, with a change in FEV₁ of -5.5 mL per interquartile range pollen increase (95% CI, -9.6 to -1.3). Similarly, cumulative pollen exposure over 3 days was associated with decreased lung function, with a change of -4.9 mL in FEV₁ (95% CI, -9.6 to -0.2).

The associations between increased pollen levels and decreased FEV₁ were even stronger in the subgroup of individuals with higher C-reactive protein levels and asthma diagnoses. The strongest associations between pollen and lung function among patients with overlapping COPD and asthma was not surprising, as pollen exposure has been known to trigger airway inflammation in those with allergic asthma, Rice said.

The study findings were limited by several factors including the lack of testing for clinical interventions, and the potential for misclassification of pollen levels, the researchers noted. However, the results are important in the larger context of climate change, which has been associated with longer pollen seasons and higher concentrations, they said.

“Clinicians need to make their patients aware of the increased respiratory health risk posed during high pollen days, especially in areas with heavy air pollution, as we found some evidence of greater effects of pollen on high pollution days,” said Rice. “For individual patients, ensuring access to medications for their COPD and allergic rhinitis, if applicable, in advance of the pollen season, and preventive interventions such as indoor air filtration to reduce pollen exposure may be beneficial,” she said.

Future research should assess whether air filtration, masks, medication, and avoiding high-pollen exposure can reduce pollen-related effects, as well as whether the effects of pollen on lung function are specific to patients with COPD with clinical evidence of allergy, Rice added.

Pay Attention to Pollen

Although the link between worse air quality days and negative impacts in COPD is well characterized, pollen count does not contribute to the air quality index, said Krishna Thavarajah, MD, a pulmonologist and director of the Interstitial Lung Disease Program at Henry Ford Hospital in Detroit.

However, longer pollen seasons and higher pollen counts in recent years warrant investigation of the impact of pollen on the large population of patients with COPD, said Thavarajah, who was not involved in the study.

“I would have expected the more pronounced decline in FEV₁ in those with a prior history of asthma,” said Thavarajah. “Higher levels of CRP predicted a more severe FEV₁ drop, which may reflect an increase in impact in patients with more severe COPD,” she noted.

The current study findings were limited in part by the small sample size, and larger studies with exploration of the long-term effects of higher pollen in COPD would be useful, said Thavarajah.

However, the results of the current study support the value of attention to pollen counts and their potential impact on lung impact lung function in patients with COPD, especially in those with prior history of asthma or more severe disease, she said.

Disclosure information for the authors is available in the original study publication. Thavarajah had no financial conflicts to disclose.