Environmental effects of ambient temperature and relative humidity on insulin pharmacodynamics in adults with type 1 diabetes mellitus.

OBJECTIVE: This study aimed to explore the effects of ambient temperature and relative humidity on insulin pharmacodynamics in adults with type 1 diabetes.

RESEARCH DESIGN: A 3-way, cross-over, randomised study was performed in adults with type 1 diabetes mellitus (n=10). The pharmacodynamics profile of a single dose of short-acting insulin (insulin lispro) was investigated under three environmental conditions: i) temperature: 15°C and humidity: 10%, ii) temperature: 30°C and humidity: 10%, and iii) temperature: 30°C and humidity: 60%, controlled in an environmental chamber. Euglycaemic glucose clamp technique ensured a constant blood glucose of 100 mg/dl (5.5 mmol/l). The following pharmacodynamic endpoints were calculated: maximum glucose infusion rate (GIRmax ), time to GIRmax (tGIRmax ), total area under the curve (AUC) for GIR from 0-6 hours (AUCGIR.0-6h ), and partial AUCs (AUCGIR.0-1h , AUCGIR.0-2h and AUCGIR.2-6h ).

RESULTS: Higher temperature (30o C) under 10% fixed humidity resulted in a greater GIRmax (p=0.04), a later tGIR.max (p=0.049) compared to lower temperature (15o C). Humidity did not affect any pharmacodynamic parameter. When the combined effects of temperature and humidity were explored, tGIR.max (p=0.008) occurred earlier with a lower late insulin pharmacodynamic effect (AUCGIR.2-6h , p=0.017) at temperature 15o C and humidity 10% compared to temperature 30o C and humidity 60%.

CONCLUSIONS: High ambient temperature resulted in greater insulin peak effect compared to low ambient temperature, with the contribution of high relative humidity only apparent at high ambient temperature. This suggests that patients with type 1 diabetes mellitus entering higher environmental temperatures with or without high humidity could experience more hypoglycaemic events. This article is protected by copyright. All rights reserved.