Background: Intrinsically photosensitive retinal ganglion cells (ipRGCs) control the pupillary light reflex (PLR) and synchronize sleep-wake cycles, melatonin secretion, and metabolic processes to the 24-h day. PLR abnormalities in diabetic retinopathy (DR) suggest ipRGC dysfunction. We explored whether ipRGC dysfunction in DR is associated with impaired sleep, circadian rhythms and metabolic functioning.
Methods: Healthy controls (n=6), type 2 diabetes (T2D) without DR (n=8), or T2D with at least moderate DR (n=11) participated. PLR inferred ipRGC function, HbA1c, and nocturnal urinary 6-sulfatoxymelatonin (aMT6s/creatinine ratio) were measured. Sleep was recorded by 7-day actigraphy. Dim light melatonin onset (DLMO) was assessed by sampling saliva in the 7 hours before self-reported bedtime.
Results: Mean age was 54.6±5.4 yr. The relative PLR was significantly smaller in T2D-DR (control vs. T2D-noDR vs. T2D-DR: 0.32(0.10) vs. 0.26 (0.09) vs. 0.13 (0.11), p=0.003). Nocturnal aMT6s [8.3 (3.1) vs. 14.6 (14.3) vs. 1.9 (2.1) ng/mg, p=0.001] was significantly lower in T2D-DR. Sleep was more disturbed in T2D-DR than others as reflected by higher wake time after sleep onset (p=0.024), higher fragmentation index (p=0.007) and lower sleep efficiency (p=0.030). HbA1c was similar between T2D groups. T2D-DR were more likely to have no detectable rise of salivary melatonin in the evening (normal 16% vs. DM-noDR 14% vs. DM-DR 67%, p=0.049). Smaller PLRs correlated with lower aMT6s (r=0.652, p=0.001). Among T2D, lower aMT6s and smaller PLR associated with lower sleep efficiency (p=0.029-0.046) and more fragmented sleep (p=0.028-0.066). There was no relationship between PLR or aMT6s with HbA1c in T2D. PLR was smaller in those without vs. with DMLO [0.11 (0.09) vs. 0.29 (0.09), p<0.001].
Conclusion: T2D with DR had dysregulated melatonin rhythm and disrupted sleep, which significantly correlated with the degree of ipRGC dysfunction.
S. Reutrakul: None. J.C. Park: None. F. Chau: None. T. Baynard: None. M. Priyadarshini: None. S. Crowley: None. J. McAnany: None.
University of Illinois at Chicago