Post-hypoglycemic nocturnal hyperglycemia in type 1 diabetes: the Somogyi hypothesis revisited.

Purpose: The plausibility of the Somogyi phenomenon (dawn hyperglycemia after nocturnal hypoglycemia) has been questioned. The present study used continuous glucose monitoring in patients with type 1 diabetes (T1DM) to investigate the frequency and the associated factors for post-hypoglycemic nocturnal hyperglycemia (PHNH), as well as the overall glycemic control in patients who develop PHNH.

Methods: This study analyzed the nighttime (0:00 am to 6:00 am) glycemic profile of 755 FreeStyle Libre 2 users with T1DM (429 men; median age 49 years, range 18-90 years) during a 14-day period. Patients were divided into three categories, as follows: no nocturnal hypoglycemia (< 70 mg/dL), only nocturnal hypoglycemia that was not followed by hyperglycemia (> 180 mg/dL) before 6:00 am, and ≥ 1 episode of nocturnal hypoglycemia that was followed by hyperglycemia before 6:00 am (PHNH). The patients' characteristics and the overall glycemic control in the 14-day period were also registered.

Results: A total of 248 patients (32.8%) developed PHNH during the 14-day period. Compared with patients who only had nocturnal hypoglycemia that was not followed by hyperglycemia (n = 332), patients with PHNH were younger, were less frequently diagnosed as latent autoimmune diabetes in adults (LADA), and used higher total daily doses of insulin. Patients with PHNH had longer time above range, shorter time in range, higher glucose variability, and more diurnal hypoglycemia than those who only had nocturnal hypoglycemia that was not followed by hyperglycemia before 6:00 am.

Conclusions: PHNH is frequent in T1DM, especially in young individuals. Compared to patients with other forms of nocturnal hypoglycemia, patients with PHNH have poorer glycemic control.