Continuous glucose monitoring system in free-living healthy subjects: Results from a pilot study

Background and Aim: The Continuous Glucose Monitoring System (CGMS®) (Medtronic Minimed, Northridge, CA) provides an opportunity to better understand abnormalities in glucose metabolism in both healthy subjects and those with diabetes. The aims of our study were to assess the reliability of CGMS compared to self-monitoring of blood glucose (BG) and to analyze the graphs obtained in a sample of healthy free-living subjects in order to establish the suitability of CGMS in physiological studies. Methods: Eighteen healthy adults, 12 women and six men, were enrolled in this study. Each subject performed 24-h CGMS and inserted 24 glycemic values, measured through a glucose meter, during their common daily activities. Three subjects were excluded from the analysis since they did not meet accuracy criteria. None of the participants received any advice as regard diet and physical activity. Means and standard deviations were used to summarize quantitative data. Normal distribution of data was tested with the Shapiro-Wilk W test. Differences over time and association between glucose levels with other variables were evaluated with linear regression models for repeated measures. Results: We did not find statistically significant differences between CGMS measures and meter readings. In the subjects studied the mean glucose levels increase according to age, and we found a mean increase in glucose concentration of 0.50 mg/dL for every year of age. As regards gender, men presented a 4.63% higher mean glucose concentration than women. A 1.16% higher glucose concentration for every unit (kg/m²) of body mass index (BMI) was observed in both groups. All subjects presented glucose concentrations within the established range of normal glucose levels for 91% of the total duration of CGMS. Conclusions: Our results suggest that long-term studies on larger groups of healthy subjects performing CGMS would be useful in order to better understand if BMI, daily stressors due to work or psychological stress, or other factors can influence daily BG variability and if these nonpathological alterations are related to development of glucose metabolism disorders.