Retinal Microvascular Responses to Short-Term Changes in Particulate Air Pollution in Healthy Adults

BACKGROUND: Microcirculation plays an important role in the physiology of cardiovascular health. Air pollution is an independent risk factor for the development and progression of cardiovascular diseases, but the number of studies on the relation between air pollution and the microcirculation is limited. OBJECTIVES: We examined the relationship between short-term changes in air pollution and microvascular changes. METHODS: We measured retinal microvasculature using fundus image analysis in a panel of 84 healthy adults (52% female), 22-63 years of age, during January-May 2012. Blood vessels were measured as central retinal arteriolar/venular equivalent (CRAE/CRVE), with a median of 2 measurements (range, 1-3). We used monitoring data on particulate air pollution (PM10) and black carbon (BC). Mixed-effect models were used to estimate associations between CRAE/CRVE and exposure to PM10 and BC using various exposure windows. RESULTS: CRAE and CRVE were associated with PM10 and BC concentrations, averaged over the 24 hr before the retinal examinations. Each 10-mu g/m 3 increase in PM10 was associated with a 0.93-mu m decrease (95% CI: -1.42, -0.45; p = 0.0003) in CRAE and a 0.86-mu m decrease (95% CI: -1.42, -0.30; p = 0.004) in CRVE after adjusting for individual characteristics and time varying conditions such as ambient temperature. Each 1-mu g/m 3 increase in BC was associated with a 1.84-mu m decrease (95% CI: -3.18, -0.51; p < 0.001) in CRAE. CONCLUSIONS: Our findings suggest that the retinal microvasculature responds to short-term changes in air pollution levels. These results support a mechanistic pathway through which air pollution can act as a trigger of cardiovascular events at least in part through effects on the microvasculature.