Nocturnal Hypoglycemia: Characterization with Continuous Glucose Monitoring in a Real-World Setting

Background: Nocturnal hypoglycemia is a common complication in people with diabetes. The use of continuous glucose monitoring (CGM) has reduced the frequency of hypoglycemia and improved its clinical characterization; however, available CGM data mostly focus on overall or diurnal hypoglycemia in people with type 1 diabetes (T1D). This real-world study compared the frequency and duration of nocturnal versus diurnal hypoglycemia in people with T1D or type 2 diabetes (T2D) and evaluated the subsequent impact of nocturnal hypoglycemia on daytime glucose profiles. Methods: Between January 2010 and September 2023, CGM data during the first month of use were collected retrospectively from people with T1D (n = 3696) or T2D (n = 441) using multiple daily insulin injections. Hypoglycemic events were identified as CGM readings: <70 mg/dL or <54 mg/dL for at least 15 min. The incidence and duration of hypoglycemic events were calculated for diurnal and nocturnal periods. The effect of nocturnal hypoglycemic events on glycemia the following day was assessed. Results: Nocturnal hypoglycemia occurred less frequently than diurnal events in both persons with T1D (median [interquartile range, IQR] 0.54 [0.0, 1.5] vs. 2.25 [0.64, 5.25] events per week) and those with T2D (median [IQR] 0 [0.0, 0.52] vs. 0.30 [0.0, 1.21] events per week). In T1D, nocturnal hypoglycemia events had a 65-min median duration compared with 40 min for diurnal events (P < 0.001). Similar trends were observed in T2D, with nocturnal hypoglycemia events lasting 57 min versus 40 min diurnally (P < 0.001). Significant changes in multiple glycemic parameters were observed during days following nocturnal hypoglycemic events versus days following nights without hypoglycemia. These findings suggest a heightened risk of morning hypoglycemia following nocturnal hypoglycemia. Conclusion: These results showed that nocturnal hypoglycemia is characterized by longer duration and slower recovery than daytime hypoglycemia, with significant effects on next-day glycemic control, which emphasizes the need for improved prevention strategies.