Glucose Changes and Working Memory in Individuals with Type 1 Diabetes During Air Pressure Changes Simulating Skydiving

Abstract

Background:

Several countries restrict individuals with type 1 diabetes mellitus (T1DM) from skydiving because of concerns over possible alterations in consciousness. To our knowledge, glucose levels and working memory in individuals with T1DM during skydiving have not been assessed earlier. The objective of this study was to investigate changes in glucose levels and working memory in selected subjects with T1DM compared with control subjects without diabetes mellitus (DM) during ambient air pressure changes as those anticipated during standard skydiving.

Subjects and Methods:

Six subjects with T1DM and six controls were included. Using a hypobaric chamber, the ambient air pressure was changed to simulate a standard skydive from 4,000 m (13,000 feet) above mean sea level. The procedure was repeated six times to mimic a day of skydiving activity with a median of 8.7 h/day (5^th, 95^th percentile: 8.1, 9.8 h). All subjects carried a continuous glucose monitor (CGM). Capillary glucose tests were taken in order to calibrate the CGM. Hemoglobin oxygen saturation, heart rate, and working memory, evaluated through digit span, were monitored regularly.

Results:

No subject experienced documented symptomatic hypoglycemia with impaired working memory during the simulations. One asymptomatic hypoglycemia episode with a plasma glucose level of <3.9 mmol/L was recorded in a subject with T1DM, with a corresponding CGM trend indicating declining glucose levels. Interstitial glucose levels of <3.9 mmol/L were recorded by CGM in three of the controls during the simulations. There were no significant differences in hemoglobin oxygen saturation, heart rate, or working memory between the T1DM patients and the controls.

Conclusions:

This study of interstitial glucose levels and working memory could not show the activity-specific risk factor (i.e., repetitive rapid-onset hypobaric hypoxia exposures) to be a greater safety concern for selected subjects with T1DM compared with subjects without DM during a simulated day of skydiving. Further studies are needed to clarify the suitability of subjects with T1DM to participate in this air sport.