Aims: To examine the effects of extreme altitude mountaineering on glycaemic control in Type 1 diabetes, and to establish whether diabetes predisposes to acute mountain sickness (AMS).
Methods: Fifteen people with Type 1 diabetes and 22 nondiabetic controls were studied during the Diabetes Federation of Ireland Expedition to Kilimanjaro. Daily insulin requirements, blood glucose estimations and hypoglycaemic attacks were recorded in diaries by the people with diabetes. The performance of blood glucose meters at altitude was assessed using standard glucose solutions. Symptoms of acute mountain sickness were recorded daily by people with diabetes and by the nondiabetic controls using the Lake Louise Scoring Charts. The expedition medical team recorded the incidence of complications of altitude and of diabetes. The final height attained for each individual was recorded by the expedition medical team and verified by the expedition guides.
Results: The final altitude ascended was lower in the diabetic than the nondiabetic group (5187 +/- 514 vs. 5654 +/- 307 m, P = 0.001). The mean daily insulin dose was reduced from 67.1 +/- 28.3-32.9 +/- 11.8 units (P < 0.001), but only 50% of recorded blood glucose readings were within the target range of 6-14 mmol/L. There were few hypoglycaemic attacks after the first two days of climbing. Both blood glucose meters tested showed readings as low as 60% of standard glucose concentrations at high altitude and low temperatures. The Lake Louise questionnaires showed that symptoms of AMS occurred equally in the diabetic and nondiabetic groups. There were two episodes of mild diabetic ketoacidosis; two of the diabetic group and three of the nondiabetic group developed retinal haemorrhages.
Conclusions: People with Type 1 diabetes can participate in extreme altitude mountaineering. However, there are significant risks associated with this activity, including hypoglycaemia, ketoacidosis and retinal haemorrhage, with the additional difficulties in assessing glycaemic control due to meter inaccuracy at high altitude. People with Type 1 diabetes must be carefully counselled before attempting extreme altitude mountaineering.