Do high fasting glucose levels suggest nocturnal hypoglycaemia? The Somogyi effect-more fiction than fact?
Level 3 - non-randomized controlled study
Non-randomized observational comparative study analyzing continuous glucose monitoring data
PubMed 23672623 · doi:10.1111/dme.12175
What was done
Continuous glucose monitoring (CGM) data from 89 patients with Type 1 diabetes enrolled in the UK Hypoglycaemia study were analyzed. Researchers compared morning fasting capillary blood glucose levels following nights with nocturnal hypoglycemia (sensor glucose < 3.5 mmol/l) against nights without hypoglycemia.
What was found
Fasting capillary blood glucose was significantly lower following nights with nocturnal hypoglycemia than nights without [5.5 (3.0) vs. 14.5 (4.5) mmol/l, P < 0.0001]. Fasting glucose was also lower after more severe hypoglycemia compared to milder episodes [5.5 (3.0) vs. 8.2 (2.3) mmol/l; P = 0.018 for nadir < 2.2 vs. 3.5 mmol/l]. Only two instances of morning glucose > 10 mmol/l occurred after nocturnal hypoglycemia, both likely attributable to hypoglycemia treatment. When fasting capillary glucose was < 5 mmol/l, nocturnal hypoglycemia had occurred on 94% of nights.
Why it matters
These findings challenge the traditional Somogyi hypothesis, showing that morning hyperglycemia is rarely a rebound from nocturnal hypoglycemia and that low morning glucose strongly indicates preceding silent overnight hypoglycemic episodes.
Limits
This was an observational secondary analysis of an existing trial cohort with a modest sample size (n = 89). The abstract does not specify the total number of monitored nights, long-term clinical outcomes, or whether findings apply to insulin-treated Type 2 diabetes.
Cited by
- context The Somogyi effect occurs when blood sugar drops very low in the early morning, triggering reactive fasting hyperglycemia.