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Michael Leonard Ferm, Manan Shah, Jaclyn Hunter Cope, Bernard Szirth, Albert S Khouri; Retinopathy correlation to frequency and severity of blood glucose spikes in Type 1 Diabetes using continuous glucose monitors. Invest. Ophthalmol. Vis. Sci. 2017;58(8):58.
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© ARVO (1962-2015); The Authors (2016-present)
Type 1 Diabetes mellitus (T1D) requires constant administration of insulin to maintain normal blood glucose (BG) levels and avoid hyperglycemic sequelae. Management protocols use glycated hemoglobin (HbA1c) and glucometer readings as an indicator of BG control, but with the advent of continuous glucose monitors (CGMs), studies can be conducted examining BG spikes. We analyzed data over a period of 90 days comparing the frequency and severity of BG spikes to retinal changes observed on retinal imaging.
Twenty-three subjects (9M-14F) with T1D for a duration of >10 years (avg=17 y, max=36 y) ranging in ages 11 to 52 (avg=23 y) were monitored with Dexcom G4/G5 CGMs over 90 days (average use = 56/90 days). BG data from Dexcom Clarity was exported and analyzed with a proprietary software (Manan Shah) that determined the number of times per day subjects’ BG rose above 250, 300, 350, and 400 mg/dL. Subjects were separated into two groups: those without (N=16) and those with (N=7) apparent retinal hemorrhages and intraretinal microvascular abnormalities (IRMA) on color and fundus autofluorescence imaging performed on day 90. Two-sample t-tests were used for statistical analysis.
The frequency of spikes over 400 mg/dL was significantly different between the group without retinopathy (1 spike/9.9 days) and the group with retinopathy (1 spike/2.6 days, p<0.05). The differences in frequency of spikes over 350 mg/dL (p=0.08), 300 mg/dL (p=0.20), and 250 mg/dL (p=0.85) were not significantly different between the groups. There was no significant difference in the average estimated HbA1c reported by Dexcom for the group without retinopathy (7.8%) and the group with retinopathy (7.9%, p=0.78). The retinopathy group showed retinal hemorrhages, but no IRMA were noted.
Our findings indicate that BG spikes over 400 mg/dL are a significant risk factor for retinopathy in subjects with T1D >10 years duration, independent of HbA1c level in this cohort. Furthermore, suggested treatments of T1D should focus on avoiding BG spikes as well as maintaining a lower HbA1c. Data extracted from CGMs and analyzed through software may prove to be beneficial for the general practitioner and endocrinologist. Further investigation will be performed on larger populations for longer durations.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Data comparing spike frequency in each group
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