Effect of HEPA Filtration Air Purifiers on Blood Pressure: A Pragmatic Randomized Crossover Trial

Particulate matter (PM) pollution is a leading cause of cardiovascular risk and illness, including elevated blood pressure (BP).

The purpose of this study was to test the efficacy of in-home air purifiers to reduce BP for adults living adjacent to highways.

We conducted a pragmatic randomized crossover trial of the effect of high-efficiency particulate arrestance (HEPA) vs sham filtration on BP. Residences were randomized to start with 1 month of HEPA filtration or 1 month of sham filtration. A 1-month wash out period with no filtration was followed by 1 month of the alternate filtration. Participant questionnaire data and BP were collected 4 times, at the start and end of each filtration period. PM concentrations were measured in a subset of residences. Linear mixed models were used to compare the mean change in BP between the HEPA and sham filtration periods. Models were adjusted for time invariant and time-varying covariates.

A total of 154 participants were analyzed. The mean age was 41.1 years, 59.7% were women, 68.2% were non-Hispanic White, and a majority were of higher socioeconomic status. The mean baseline brachial systolic blood pressure (SBP)/diastolic BP was 118.8/76.5 mm Hg. HEPA filtration significantly reduced PM in comparison to both indoor sham and outdoor levels. Participants' SBP at the start of the intervention period moderated the efficacy of the intervention (P = 0.03). Participants who had elevated brachial SBP (≥120 mm Hg) had a significant 2.8-mm Hg mean reduction in SBP after HEPA filtration (P = 0.03) and a 0.2-mm Hg mean increase in SBP after sham filtration (P = 0.85). The net result was a significant 3.0-mm Hg mean difference in favor of HEPA filtration (P = 0.04). There was no significant benefit on diastolic BP or for participants with normal SBP (<120 mm Hg).

The use of in-home HEPA air purifiers resulted in clinically important reductions in SBP for people with elevated SBP in environments with relatively low PM_2.5 concentrations.