Cranking the Heat Indoors Worsens COPD Symptoms

As fall has arrived and winter is steadily approaching, turning on the heat inside will soon become a necessity.

In a new study published in Annals of American Thoracic Society, researchers reported on a longitudinal analysis that included 69 participants with moderate-to-severe chronic obstructive pulmonary disease (COPD) during the hottest days of the year.

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

For the study, participants were required to complete a daily questionnaire that included the Breathlessness, Cough, and Sputum Scale (BCSS), which provided a standardized rating of respiratory symptoms. Study participants also performed daily spirometry to assess their function, and recorded their use of rescue inhalers to manage symptoms.

This information was then analyzed along with measurements of 2 air pollutants in their homes called, fine particulate matter (PM2.5) and nitrogen dioxide (NO2), as well as outdoor temperatures during the study period. The results of the analysis showed that participants spend an overwhelming majority of time indoors, and for the days they did go out, they spend on average about 2 hours.

The BCSS scores worsened as indoor temperatures increased. Furthermore, the use of rescue inhalers also increased.

Researchers found that the effect of higher indoor temperatures was magnified by high levels of PM2.5 and NO2. In a home at the 75^th percentile of PM2.5 levels, a 10-degree increase in temperature resulted in a severe increase in symptoms, compared with a mild increase in symptoms that occurred when the home was at the 25^th percentile of PM2.5

The effects of the higher indoor temperatures were immediate, and continued for 1 to 2 days in patients. However, lung function measured by spirometry was unaffected by increasing temperatures, or higher levels of indoor air pollutants.

There were 86% of participants who lived in a home with some form of air conditioning; however, they did not turn it on during 37% of study days. Additionally, researchers found that even the short time that participants spent outdoors led to respiratory symptoms on hotter days.

A potential limitation to the study included being geographically confined to Baltimore, MD, as well as the decision to not measure indoor ozone levels, since prior studies found those levels to be low indoors in the city.

The study authors noted that the findings may present health care professionals with an opportunity for targeted interventions. The study also suggests that policymakers need to develop mitigation strategies to protect individuals who are most vulnerable to heat.

“Given the 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,” McCormack said.