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BACKGROUND A growing number of subjects with diabetes take part in physical activities at altitude such as skiing, climbing, and trekking. Exercise under conditions of hypo-baric hypoxia poses some unique challenges on subjects with diabetes, and the presence of diabetes can complicate safe and successful participation in mountain activities. Among others, altitude can alter glucoregulation. Furthermore, cold temperatures and altitude can complicate accurate reading of glucose monitoring equipment and storage of insulin. These factors potentially lead to dangerous hyperglycemia or hypoglycemia. Over the last years, more information has become available on this subject. PURPOSE To provide an up-to-date overview of the pathophysiological changes during physical activity at altitude and the potential problems related to diabetes, including the use of (continuous) blood glucose monitors and insulin pumps. To propose practical recommendations for preparations and travel to altitude for subjects with diabetes. DATA SOURCES AND SYNTHESIS We researched PubMed, medical textbooks, and related Internet sites, and extracted human studies and data based on relevance for diabetes, exercise, and altitude. LIMITATIONS Given the paucity of controlled trials regarding diabetes and altitude, we composed a narrative review and filled in areas lacking diabetes-specific studies with data obtained from nondiabetic subjects. CONCLUSIONS Subjects with diabetes can take part in activities at high, and even extreme, altitude. However, careful assessment of diabetes-related complications, optimal preparation, and adequate knowledge of glycemic regulation at altitude and altitude-related complications is needed. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Safe, very high altitude trekking in subjects with type 1 diabetes requires understanding of glucose regulation at high altitude. We investigated insulin requirements, energy expenditure, and glucose levels at very high altitude in relation to acute mountain sickness (AMS) symptoms in individuals with type 1 diabetes. RESEARCH DESIGN AND METHODS--Eight individuals with complication-free type 1 diabetes took part in a 14-day expedition to Mount Meru (4,562 m) and Mount Kilimanjaro (5,895 in) in Tanzania. Daily insulin doses, glucose levels, energy expenditure, and AMS symptoms were determined. Also, energy expenditure and AMS symptoms were compared with a healthy control group. RESULTS--We found a positive relation between AMS symptoms and insulin requirements (r = 0.78; P = 0.041) and AMS symptoms and glucose levels (r = 0.86; P = 0.014) for Mount Kilimanjaro. Compared with sea level, insulin doses tended to decrease by 14.2% (19.7) (median [interquartile range]) (P = 0.41), whereas glucose levels remained stable up to 5,000 m altitude. However, at altitudes >5,000 m, insulin dose was unchanged (36.8 ± 17 vs. 37.6 ± 19.1 international units [mean ± SD] P = 0.75), but glucose levels (7.5 ± 0.6 vs. 9.5 ± 0.8 mmol/L [mean ± SD] P = 0.067) and AMS scores (1.3 ± 1.6 vs. 4.4 ± 4 points [mean ± SD] P = 0.091) tended to increase. Energy expenditure and AMS symptoms were comparable in both groups (P = 0.84), CONCLUSIONS--Our data indicate that in complication-free individuals with type 1 diabetes, insulin requirements tend to increase during altitudes above 5,000 m despite high energy expenditure. This change may be explained, at least partly, by AMS. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Limited information is available regarding the metabolic effects of high altitude trekking in patients with type 2 diabetes. RESEARCH DESIGN AND METHODS--Thirteen individuals with type 2 diabetes took part in a 12-day expedition to the summit of Mount Toubkal (altitude, 4,167m), Morocco, after 6 months of exercise training. Energy expenditure, body weight, blood glucose, fasting insulin, lipids, and HbA1c were assessed. RESULTS--Training reduced fasting glucose (-0.7 ± 0.9 mmol/L, P = 0.026) and increased exercise capacity (+0.3 ± 0.3W/kg, P = 0.005). High altitude trekking decreased fasting insulin concentrations (-3.8 ± 3.2 µU/L, P = 0.04), total cholesterol (-0.7 ± 0.8 mmol/L, P = 0.008) , and LDL cholesterol (-0.5 ± 0.6 mmol/L, P = 0.007). CONCLUSIONS--High altitude trekking preceded by exercise training is feasible for patients with type 2 diabetes. It improves blood glucose, lipids, and fasting insulin concentrations, while glucose control is maintained. [ABSTRACT FROM AUTHOR]