Anaemia and the risk of progression from non-proliferative diabetic retinopathy to vision threatening diabetic retinopathy

Background/Aims To determine if anaemia and oxygen delivery-related co-morbidities (ODCs) affect progression from non-proliferative diabetic retinopathy (NPDR) to vision-threatening diabetic retinopathy (VTDR). Methods This is a retrospective cohort study using medical claims data from a large US insurer. Cohorts were created from all NPDR patients between 2002 and 2016. Primary exclusion criteria consisted of any previous diagnosis of proliferative diabetic retinopathy (PDR), diabetic macular oedema (DME) or treatment used in the care of VTDR. The main outcome was a new diagnosis of VTDR (DME or PDR), PDR, or DME. A time-dependent, multivariate Cox proportional hazard regression was used to determine the association between anaemia and other ODCs with NPDR progression. Results Of the total 69,982 NPDR patients included for analysis, 12,270, 2,162, and 10,322 progressed to VTDR, PDR and DME, respectively. Both mild and moderate/severe (mod/sev) anaemia were associated with an increased hazard for progression to VTDR (mild HR:1.10, 95% CI:1.04-1.16, p < 0.001; mod/sev HR:1.20, 95% CI:1.12-1.29, p < 0.001), PDR (mild HR:1.29, 95% CI:1.13-1.46, p < 0.001; mod/sev HR:1.43, 95% CI:1.21-1.69, p < 0.001), and DME (mild HR:1.06, 95% CI:1.00-1.13, p < 0.001; mod/sev HR:1.14, 95% CI:1.05-1.24, p < 0.001). ODCs such as chronic pulmonary disease and history of blood disorder/cancer were also significantly associated with an increased hazard for NPDR progression (HR > 1.00, p < 0.001 for all comparisons). Conclusions Anaemia, independent of kidney disease, appears to play a significant role in progression from NPDR to VTDR, PDR, or DME. Concurrently, association of ODCs with NPDR progression lends support to the underlying mechanisms of anaemia in the pathogenesis of diabetic retinopathy.