Geriatric patients with type 2 diabetes with lower fasting glucose and estimated glomerular filtration rate are at risk of developing clinically significant nocturnal hypoglycemia, according to a study from Japan published in The Journal of Diabetes and Its Complications.^1,2 Insulin use also heightened this risk.

In this study, various risk factors for clinically significant nocturnal hypoglycemia were examined in 606 adults with type 2 diabetes, aged ≥65 years. A Freestyle Libre Pro CGM was used to monitor blood glucose for 14 days from October 2018 to February 2020. Blood glucose level <54 mg/dL (3.0 mmol/L) between midnight and 6 am was taken as clinically significant nocturnal hypoglycemia. A multivariate logistic regression analysis was used to define the association. Of the 606 patients evaluated, 152 were in the top quartile for highest frequency of clinically significant nocturnal hypoglycemia and were classified as nocturnal hypoglycemia group, while those in the lowest quartile were classified as non-nocturnal hypoglycemia.

Compared to the non-nocturnal hypoglycemia patients, those who experienced clinically significant nocturnal hypoglycemia had lower mean glucose 114.86 mg/dL vs 88.09 mg/dL. The blood glucose remained below the range for a longer period of time.  

On multivariate analysis, patients taking insulin were nearly 4-times more likely to develop nocturnal hypoglycemia with odds ratio of 3.77. Older adults almost doubled their risk of nocturnal hypoglycemia with OR 1.06. Other factors such as estimated glomerular filtration rate and fasting blood glucose level were also independently associated with increased risk of nocturnal hypoglycemic events with OR of 0.97 and 0.94, respectively. When combined together their risk prediction of clinically significant nocturnal hypoglycemia was stronger than when they were considered individually.

Use of insulin was found to influence the occurrence of clinically significant nocturnal hypoglycemia. Age >69 years, fasting blood glucose <91 mg/dL and eGFR < 41.2 mL/min/1.73 m² were the cut-offs to predict clinically significant nocturnal hypoglycemia among those who used insulin. Among the non-insulin users, the cut-offs were age >79 years, FBG <92 mg/dL and eGFR <70.93 mL/min/1.73 m².

Nocturnal hypoglycemia is common in patients with type 2 diabetes and often goes unrecognized. Avoiding hypoglycemia in the older patients is of greater significance compared to the long-term risk of microvascular complications. This case-control retrospective observational study has identified independent risk factors - age, fasting blood glucose level, insulin use, and kidney function - for clinically significant nocturnal hypoglycemia in older patients with type 2 diabetes. Awareness about factors that raise the risk of nighttime hypoglycemia and proper treatment planning e.g., timing of insulin administration can reduce the risk of nocturnal hypoglycemia. Patients and their caregivers should be educated to recognize the signs of nocturnal hypoglycemia. Nocturnal hypoglycemia may also be a significant cause of nighttime falls in this age group.

 References 

1. Ken Kanazawa, et al. A comprehensive risk assessment for nocturnal hypoglycemia in geriatric patients with type 2 diabetes: A single-center case-control study. J Diabetes Complications. 2022 Aug;36(8):108239. doi: 10.1016/j.jdiacomp.2022.108239.
2. https://www.healio.com/news/endocrinology/20220809/insulin-use-older-age-raise-risk-for-clinically-significant-nocturnal-hypoglycemia, August 9, 2022.
3. K Alagiakrishnan, et al. Atypical presentation of silent nocturnal hypoglycemia in an older person. J Am Geriatr Soc. 2001 Nov;49(11):1577-8. doi: 10.1046/j.1532-5415.2001.4911263.x.