Using Indoor Air Filtration to Slow Atherothrombosis Progression in Adults With Ischemic Heart Disease History

This double-blind, randomized, crossover trial will recruit 112 adults with ischemic heart disease history and will investigate potential benefits of indoor high efficiency particulate air (HEPA) filtration on ameliorating the progression of atherothrombosis. Participants will be contacted and recruited to the study based on inclusion and exclusion criteria. After consenting, participants will go through a total of 21-month study period comprised of true HEPA filtration and sham filtration, each of 9-month in duration, and a 3-month wash-out period. After 3-month wash-out period, participants will be switched to the other arm of the intervention. During the trial, project specialists will complete a series of home visits before, in the middle, and after each intervention session to set up air purifiers and indoor and outdoor air pollution monitors, as well as conduct interview to collect questionnaire data, measure vascular function, blood pressure, and collect biospecimens. Participants will self-monitor their daily blood pressure through out the intervention periods. In aim 1, researchers will assess the effect of a 9-month residential HEPA intervention on atherothrombosis progression in 112 participants. In aim 2, the researchers will examine the association between reduction in indoor PM2.5 exposure brought by the intervention and the changes in atherothrombosis progression indicators adjusting for outdoor PM2.5 exposure. In aim 3, researchers will examine atherothrombosis responses (both levels and slopes of change) to the HEPA intervention within four subgroups of participants: 1) non-Hispanics, 2) Hispanics, 3) females, and 4) males.