MON-610 - Seasonal and Day of the Week Differences in Continuous Glucose Monitoring Metrics for Individuals without Diabetes

Background: While seasonal patterns in glycemic burden have been observed among individuals with diabetes via continuous glucose monitoring (CGM), less is known about such variations among individuals without diabetes. We investigated glycemic burden via CGM by month and day of the week in individuals who have either prediabetes or normoglycemia.

Methods: Framingham Heart Study participants without diabetes or taking glucose-lowering medication were included if they wore a Dexcom G6 Pro sensor for 7 full days (n=1550). We stratified participants by glycemic status (normoglycemia or prediabetes) based on hemoglobin (Hb)A1c and fasting plasma glucose. We estimated least squares means (LS-means) for 6 CGM metrics including mean glucose and time spent above 140 mg/dL, by month and day of the week, adjusting for age, sex, HbA1c, body mass index (BMI), CGM location on arm vs. abdomen, and CGM lot number. We assessed differences in adjusted means of monthly and day of the week CGM metrics using analysis of covariance and stratifying by glycemic status. We then assessed the respective mean monthly differences compared to July/August (referent).

Results: Individuals with prediabetes (n=673, 44.9% women, mean age 61.9 years, and BMI 29.6 kg/m2) were older and had a higher BMI than those with normoglycemia (n=877, 66.2% women, mean age 58.4 years, and BMI 26.7kg/m2) in our cohort. CGM metrics were consistently different by glycemic status, with individuals with prediabetes exhibiting 9.4 mg/dL (SE=0.7) higher mean glucose and spending 10% (SE=0.8) more time above 140 mg/dL compared to individuals with normoglycemia (all p< 0.001). Month-to-month analyses demonstrated significant seasonal variation in glycemic burden for participants with prediabetes, but not among normoglycemia. Participants with prediabetes who wore the CGM during July or August had 6.4 mg/dL (SE=1.5 mg/dL) higher mean glucose and spent 7.6% (SE=2.0%) more time above 140 mg/dL compared to those wearing a CGM during other months of the year (all p< 0.001), after adjustments. There were no differences in CGM metrics by day of the week for those with prediabetes or normoglycemia (p>0.05).

Conclusion: Among individuals with prediabetes, we observed distinct seasonal patterns of glycemic burden, with higher glycemic fluctuations during the summer. Future studies will be needed to assess whether climate or temperature affect CGM accuracy or whether hydration status or participant behaviors explain the higher glycemic burden we observed in the summer months.

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