Indoor Overheating and Physiological Strain in Older Adults With COPD

During warm weather, homes without air conditioning can stay hot for long periods, and most heat-related health problems in Canada happen indoors rather than outdoors. Health Canada recommends that indoor temperatures not exceed 26 °C in homes occupied by people who are more susceptible to heat. That recommendation is based largely on population-level evidence, and very little is known about how susceptible individuals actually respond, physiologically, when indoor temperatures rise above it. Older adults living with chronic obstructive pulmonary disease (COPD) are among the groups identified as more susceptible to heat. COPD involves persistent airflow limitation, reduced lung and cardiovascular reserve, and altered cellular stress responses. Despite this, no laboratory study has directly measured how adults with COPD respond to a full day spent indoors in warm conditions. This randomized crossover trial will measure how older adults with COPD respond to two different indoor environments, each experienced for eight hours on separate days at least one week apart. One day is spent at the recommended indoor temperature limit and the other at a warmer temperature representative of conditions recorded inside Canadian homes during hot weather. Participants remain seated and rest throughout; no exercise or work is performed. Throughout each day, the research team continuously measures core body temperature, skin temperature, heart rate, and measures blood pressure, lung function, breathlessness, thermal comfort, cognitive performance, and balance at set time points. Blood and urine samples are collected at the start and end of each day. Participants are monitored continuously by trained staff. The results are intended to strengthen the evidence base behind Canadian indoor temperature guidance and to inform recommendations for protecting people living with chronic lung disease during hot weather.

Inclusion Criteria: * Aged 60 to 80 years * Physician diagnosis of chronic obstructive pulmonary disease made at least 5 years previously * Clinically stable, with no acute exacerbation or active respiratory infection in the preceding 6 weeks * Current non-smoker * Able to communicate in English or French and to provide written informed consent Exclusion Criteria: * Physical restriction preventing safe participation, including unstable cardiac or pulmonary disease, uncontrolled hypertension (resting blood pressure exceeding 150/95 mmHg), severe arthritis, renal impairment, active proliferative retinopathy, history of disabling stroke, or intermittent claudication * Recent change in medications judged by the investigators to make participation inadvisable * Cardiac abnormalities identified on electrocardiogram during the screening exercise test * Regular work or exercise in hot environments (heat acclimatized)