High indoor temperatures may worsen COPD symptoms

Patients with chronic obstructive pulmonary disease who live in homes with higher indoor temperatures, as well as high levels of air pollutants, develop worse symptoms of the disease, according to study results published in Annals of the American Thoracic Society.

“Previous studies have found that the elderly are particularly vulnerable to the effect of heat and more likely to die or be hospitalized during heat waves,” Meredith C. McCormack, MD, MHS, associate professor of medicine at Johns Hopkins University said. “Our study builds on these findings by investigating exposure at the individual level, including in-home assessment of temperature and specific health effects of chronic obstructive pulmonary disease (COPD). To our knowledge, this is the first study to report an interactive effect between indoor temperature and indoor air pollution in COPD.”

A total of 69 patients with moderate to severe COPD were enrolled in a longitudinal study, which was conducted during the hottest days of the year. The participants completed a daily questionnaire to rate their respiratory symptoms using the Breathlessness, Cough and Sputum Scale (BCSS), documented their use of rescue inhalers to manage COPD–related symptoms and assessed their lung function through daily spirometry tests.

In addition to this data, outdoor temperatures and two air pollutants found in the homes of participants including fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) were measured and evaluated by McCormack and colleagues.

Results show that BCSS scores and use of rescue inhalers increased as indoor temperatures rose. In addition, high levels of PM_2.5 and NO₂ intensified the impact of raised indoor temperatures. Symptoms caused by high indoor temperatures were immediate and lasted for up to two days.

However, spirometry assessments revealed that lung function was not affected by higher indoor temperatures nor higher levels of PM_2.5 and NO₂.

The investigators discovered that participants spent most of their time indoors—only going outdoors for an average of 2 hours per day, if at all. On hotter days, respiratory symptoms worsened regardless of the amount of time spent outdoors, according to McCormack and colleagues.

Air conditioning was not used during 37% of the study days even though 86% of participants had an air conditioning system in their home.

“Given that participants spent an overwhelming majority of their time indoors, which we believe is representative of patients with COPD generally, optimizing indoor climate and reducing indoor pollution represents a potential avenue for improving health outcomes,” Dr. McCormack concluded. – by Alaina Tedesco

Disclosure: The researchers report funding by the National Institute of Environmental Health Sciences and the Environmental Protection Program.