Waist circumference moderates IL-1 beta response to HEPA filtration in near-highway residents

The University of Connecticut–Tufts study enrolled residents living within 200 m of Interstate 93 and used a 30-day true versus sham HEPA crossover design. Primary outcome was change in plasma cytokines; initial intent-to-treat analysis found no overall effect. Stratification by waist-to-height ratio revealed effect modification: individuals above the visceral-fat threshold showed reduced IL-1 beta, consistent with the hypothesis that pre-existing adipose-driven inflammation amplifies ultrafine-particle effects.

Visceral adipose tissue secretes IL-1 beta and other cytokines that prime endothelial and microglial cells, lowering the threshold at which inhaled nanoparticles trigger systemic responses. This interaction explains why the same exposure produces divergent cardiovascular and cognitive outcomes across BMI categories and aligns with larger cohort findings linking central adiposity to pollution-attributable mortality in the Nurses’ Health Study and ESCAPE meta-analyses.

The team has launched a follow-up pragmatic trial in Hartford and Boston testing low-cost box-fan filters. Primary endpoint remains IL-1 beta change at 30 days, with pre-specified subgroup analysis by waist-to-height ratio and baseline blood pressure. Results are expected in 2027 and will test whether the moderation effect replicates under real-world filtration conditions.

Commercial HEPA units remain costly; identifying the visceral-fat subgroup offers a practical targeting strategy while the cheaper filter trial matures.