The Relationship Between Nocturnal Hypoglycemia And Cognitive Function In Aged Type 2 Diabetic Patients Using Continuous Glucose Monitoring System

OBJECTIVE: To investigate the relationship between nocturnal hypoglycemia and cognitive function in aged type 2 diabetic patients using continuous glucose monitoring system(CGMS).METHODS: A total of 211 aged patients with type 2 diabetes were recruited in this study, all of whom were monitored under CGMS for 3 days. According to the definition, a hypoglycemia episode was recorded when CGM glucose level was ?3.9 mmol / L and lasted at least 20 min. The event that hypoglycemia occurred in 21:00 to 6:00 was recorded as nocturnal hypoglycemia. During the period of CGMS monitoring, all subjects accepted Mini-Mental State Examination(MMSE) for evaluating cognitive function. Patients were then divided into two groups based on MMSE scores, a group with MMSE?24 and a group with MMSE>25. The correlation between hypoglycemia(and nocturnal hypoglycemia) and cognitive test was evaluated statistically.RESULTS: We found that hypoglycemia was recorded in 100 cases out of 211 patients, and of which 82(82.00%) cases were recorded as nocturnal hypoglycemia. The hypoglycemia group showed lower MMSE score than the normal group(25.14±5.09 vs 26.77±2.98, p < 0.05). Furthermore, the incidence of hypoglycemia(or nocturnal hypoglycemia) was higher in the group with MMSE?24 than those with MMSE>24(63.8% vs 42.7% for hypoglycemia,51.1% vs 35.4% for nocturnal hypoglycemia, p<0.05). The median of hypoglycemia maximum time and nocturnal hypoglycemia maximum time were longer in the group of MMSE?24 than those with MMSE>24(40 vs 0 min for hypoglycemia, 20 vs 0 min for nocturnal hypoglycemia, p<0.05). Patients with hypoglycemia occurred in a nocturnal period(00:00-03:00) showed lowered MMSE score(p<0.05). In addition, stepwise regression analysis showed that the total time and maximum time of hypoglycemia(or nocturnal hypoglycemia), age, and education level were the main factors, in correlation with MMSE score.CONCLUSION: Hypoglycemia, which correlated with decreased MMSE score, may threaten cognitive function in aged type 2 diabetic patients. Especially, the high incidence and the long lasting time of hypoglycemia(and nocturnal hypoglycemia, especially in a nocturnal period(00:00-03:00)) would play an important role in the development of cognitive impairments. Monitoring of hypoglycemia(especially nocturnal hypoglycemia) by using CGMS would be beneficial for improving cognitive function in aged patients with type 2 diabetes.