Ambient temperature may influence short-term glycemic patterns in people with type 1 diabetes mellitus (T1DM), with implications for day-to-day management. A case time series analysis published in Diabetes Care evaluated the association between ambient temperature and hypoglycemia using continuous glucose monitoring (CGM) data from 679 adults with T1DM attending two National Health Service clinics in Sussex, England, between 2017 and 2024.

The analysis incorporated 32,966,282 glucose readings. Hypoglycemia was defined as at least 15 minutes of glucose levels below 3.9 mmol/L. A quasi-binomial fixed-effect regression model with distributed lag nonlinear functions assessed both nonlinear and delayed temperature effects. The model adjusted for long-term trends, seasonality, day of the week, and public holidays. A secondary outcome examined changes in daily mean glucose concentration.

Higher ambient temperatures were associated with increased odds of hypoglycemia. The relationship was nonlinear, with risk rising above 13°C and reaching an odds ratio of 1.26 (95% CI 1.13-1.26) at 25°C. The strongest association was observed on the same day as temperature exposure, with effects diminishing over subsequent days. In the secondary analysis, higher temperatures were associated with lower mean glucose levels.

These findings indicate that elevated ambient temperature is associated with a higher short-term risk of hypoglycemia in adults with T1DM within this U.K. cohort. Geographic and climatic specificity may limit generalizability. The results support consideration of ambient temperature in insulin dose adjustments and integration into hybrid closed-loop insulin delivery systems to improve glycemic safety.