Exploring blood glucose variation over geographical space

Type 2 diabetes mellitus is known to be associated with environmental, behavioral, and lifestyle factors such as a sedentary lifestyle, overly rich nutrition, and obesity. However, the day-to-day human-environment interactions and real-life activities that cause an individual's blood glucose to fluctuate remain relatively unexplored, owing in part to data collection challenges. This article presents a novel data collection system that overcomes these challenges and allows exploration of the spatial correlates of blood glucose fluctuation.

An automated monitoring system was developed combining a Global Positioning System (GPS) receiver with a continuous blood glucose monitor. The GPS was used to elicit a second-by-second accounting of an individual's daily activities alongside blood glucose measurement every 5 min. A pilot study of 40 diabetes patients was conducted over a 72-h period. Geographic Information System software was used to generate blood glucose maps, incorporating methods to deal with scale issues, overlapping data, and to protect subject identity.

Individual blood glucose variation maps revealed a variety of distinct patterns. Most subjects had at least two major anchor points in their life combined with a variety of other activity locations at varying distances from home, many associated with quite distinct low or high blood glucose values. Further statistical analysis revealed location and distance from home were significantly correlated with blood glucose variation-although the strength and direction of the effect was quite mixed.

Results suggests that blood glucose and space/location are highly correlated and should be considered further as a lifestyle-related risk factor for diabetes patients. In the future, patients and caregivers may benefit from individualized visualization tools that help identify problematic locations that require special attention.