Abstract
BACKGROUND: Sleep-disordered breathing (SDB) is an emerging risk factor for cardiovascular disease (CVD). Microvascular dysfunction has been proposed as a potential mechanism in the pathogenesis of CVD in SDB. The retinal vasculature offers a unique opportunity to investigate the systemic effects of microvascular dysfunction as it can be viewed non-invasively and is also structurally and functionally similar to microvasculature elsewhere in the body. We therefore examined the association between SDB and retinal microvascular diameter after adjusting for major confounders. METHODS: We examined n = 476 participants from the Wisconsin Sleep Cohort Study. SDB was characterized using the apnea-hypopnea index (AHI) as <5 events/h, 5-14.9 events/h, and ≥15 events/h. Outcomes of interest included the presence of retinal arteriolar narrowing (mean retinal arteriolar diameter <141.0 um) and retinal venular widening (mean venular diameter >223.0 um). RESULTS: Higher AHI was found to be positively associated with retinal venular dilatation, independent of body mass index, hypertension, diabetes, and lipid levels. Compared to an AHI of <5 events/h (referent), the multivariable-adjusted odds ratio of retinal venular widening for an AHI of 5-14.9 events/h was 1.31 (0.75-2.28) and for an AHI of >15 events/h was 2.08 (1.03-2.16); p-trend = 0.045. In contrast, there was no association between AHI and retinal arteriolar narrowing (p-trend = 0.72). CONCLUSION: Higher AHI, a marker of SDB, was positively associated with wider retinal venules, independent of age, gender, BMI, hypertension, diabetes, and lipid levels. These data suggest that the association of SDB with cardiovascular disease may be mediated, in part, by microvasculature.