High indoor temperatures appear to worsen symptoms of chronic obstructive pulmonary disease, particularly in homes that also have high levels of air pollutants, according to US researchers.
They concluded that “optimising indoor climate and reducing indoor pollution” could help reduce the symptoms of COPD.
“Optimising indoor climate and reducing indoor pollution represents a potential avenue for improving health outcomes”
Their study, published in the journal the Annals of the American Thoracic Society, focused on 69 patients with moderate to severe COPD during the hottest days of the year in the US city of Baltimore.
Study participants completed a daily questionnaire that included the Breathlessness, Cough, and Sputum Scale (BCSS).
The patients also performed daily spirometry to assess their lung function and recorded their use of rescue inhalers to manage symptoms.
The researchers compared the results against measurements of outdoor temperatures and two indoor air pollutants – fine particulate matter (PM2.5) and nitrogen dioxide (NO2).
Overall, they found the study participants spent the overwhelming majority of their time indoors. On the days they did go out, they spent on average about two hours.
In addition, they found BCSS scores worsened with rising indoor temperatures and the use of rescue inhalers also increased.
“This is the first study to report an interactive effect between indoor temperature and indoor air pollution in COPD”
The effect of higher indoor temperatures was also magnified by high levels of PM2.5 and NO2, noted the researchers.
The effects of higher indoor temperatures were experienced immediately and continued for one to two days, they said.
However, they highlighted that lung function itself was unaffected by increasing temperatures or higher levels of indoor air pollutants.
Dr Meredith McCormack, from Johns Hopkins University, added that the study even found the short time participants spent outdoors led to respiratory symptoms on hotter days.
She suggested that the findings presented healthcare professionals with an opportunity for targeted interventions to protect those most vulnerable to heat.
“Given that participants spent an overwhelming majority of their time indoors, which we believe is representative of patients with COPD generally, optimising indoor climate and reducing indoor pollution represents a potential avenue for improving health outcomes,” she said.
She added that previous studies had found that older patients in general were particularly vulnerable to the effect of heat and more likely to die or be admitted during heat waves.
“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,” she said.
“To our knowledge, this is the first study to report an interactive effect between indoor temperature and indoor air pollution in COPD,” she said.