Randomized trial in rural Native American homes heated with wood stoves: results from the EldersAIR study.

Residential wood burning has both practical and traditional value among many indigenous communities of the United States Mountain West, although household biomass burning also results in emissions that are harmful to health. In a household-level three-arm placebo-controlled randomized trial we tested the efficacy of portable filtration units and education interventions on improving pulmonary function and blood pressure measures among elder participants that use wood stoves for residential heating. A total of 143 participants were assigned to the Education (n=49), Filter (n=47), and Control (n=47) arms. Blood pressure and spirometry measures were collected multiple times during a per-intervention winter period and during a follow-up post-intervention winter period. Despite strong PM exposure reduction results with the Filter arm (50% lower compared to Control arm), neither this intervention nor the Education intervention translated to improvements in the selected health measures among this population with a mixture of chronic conditions. Intention to treat analysis failed to demonstrate evidence that either of the intervention arms had beneficial effects on the blood pressure or the spirometry measures. Post-hoc evaluation of effect modification for blood pressure and spirometry outcomes did not reveal any interaction influence on the outcomes according to sex, residential smoking, chronic disease history and study area.