A UK study, published in the American Journal of Respiratory Critical Care Medicine (Jun 8, 2017), indicates that patients with type 2 diabetes and obstructive sleep apnoea (OSA) are at a significantly increased risk of sight-threatening diabetic retinopathy. According to the authors of the non-interventional study, the research represents the first longitudinal examination of the relationship between sleep apnoea and diabetic retinopathy (DR). In addition to uncovering a relationship between sleep apnoea and DR, the research also identified a link with maculopathy, concluding that obstructive sleep apnoea may be an independent predictor for the development of advanced DR in the type 2 diabetic population.
The research, conducted at the out-patient diabetes departments of two secondary care hospitals in the UK (Birmingham Heartlands Hospital and Royal Stoke University Hospital), recruited 266 patients with a diagnosis of type 2 diabetes, but excluded any patients with respiratory disease, end-stage renal disease or non-diabetic retinopathy. The research was designed to assess the relationship between sleep apnoea and DR, and to assess if there was any association between sleep apnoea and the progression of DR. Of the 230 patients examined, sight threatening DR and OSA prevalence was 36.1% and 63.9%, respectively however, the prevalence of sight-threatening DR was significantly higher in patients with OSA compared to patients without: (42.9% vs. 24.1%, p0.004). The research also conducted an analysis to adjust for confounders that might obscure a true relationship however, OSA remained independently associated with sight-threatening DR (OR 2.3, 95%CI 1.1-4.9, p=0.04). A further follow-up of 199 patients over a 43- month period showed that patients with OSA were over three times more likely to develop pre-/proliferative DR, compared to patients without OSA (18.4% vs. 6.1%, p=0.02).
While providing a more specific cause/effect relationship between OSA and DR was outside the scope of the study, the authors noted that hypoxaemia associated with OSA has been previously shown to be associated with increased VEGF, which plays a central role in vasculature leakage and DR progression. The authors additionally commented that OSA associated hypoxaemia primarily occurs during the hours of sleep, mostly during the night, which coincides with a time that the retina may be more prone to hypoxic damage. The data presented by the UK group additionally demonstrated that the higher prevalence of DR in patients with OSA, compared to those without OSA, appeared to be driven by a higher prevalence of advanced DR however, the authors concluded that, “the prevalence of background DR (or early DR) was similar in patients with and without OSA; suggesting that OSA contribute to the progression rather than the development of the disease. This is biologically plausible, particularly since the intermittent hypoxia associated with OSA can result in retinal ischemia and increased VEGF production resulting in the development of advanced DR.”