Continuous blood glucose monitoring may improve glycaemic control in adults, according to a controlled trial, although it did not seem to have benefits in children and adolescents.

Intensive blood glucose control has been shown to improve outcomes in people with type 1 diabetes, however achieving recommended levels of glycosylated haemoglobin (HbA1c) is still difficult. Recent continuous blood glucose monitors are more accurate, have greater functionality, and most important are better tolerated by users than older devices: this study aimed to determine whether use of such devices by patients under day-to-day conditions could improve their level of blood glucose control.

The study involved patients aged at least 8 years who had type 1 diabetes diagnosed at least a year previously, who used a insulin pump or had three or more insulin doses daily, had HbA1c levels of 7% to 10%, and who had not recently used a continuous monitoring system. They were randomised to continuous glucose monitoring (intervention) or home glucose monitoring using a standard blood glucose meter at least four times daily (control): the intervention group were provided with the monitoring device, and computer software to analyse the results if they had a home PC. Participants were stratified by age into three groups – 25 and over, 15 to 24, and 8 to 14 years. All patients were followed-up at 1, 4, 8, 13, 19, and 26 weeks (±1 week), with one telephone contact between each visit; glycaemic control and diabetes management was reviewed at each visit. Primary outcome was change in HbA1c level at 26 weeks. Statistical calculation indicated that a sample size of 110 patients in each of the three age bands would give adequate power to detect a significant difference between the intervention and study groups.

Over a ten month period, 322 patients were randomised, 165 to continuous monitoring and 157 controls. Follow-up was good, with >95% of study visits and >93% of telephone contacts completed. There was a significant difference between the groups for baseline and 26-week HbA1c levels only in the 25 and over age group: in this group, mean change in HbA1c was -0.50% for the intervention group and 0.02% for the controls, a difference of -0.53% (95% CI, –0.71 to –0.35; P<0.001). There were no significant differences between the groups for the other age bands in the primary outcome, although some secondary outcomes were improved in the youngest age group. There was also no difference between the groups in rates of severe hypoglycaemia, however the study was not powered to detect such a difference.

The authors conclude that continuous blood glucose monitoring improved glycaemic control in adult patients with type 1 diabetes. There was less benefit in children, and it did not seem to be useful in  adolescents and younger adults. The authors discuss their results, noting that it is well recognised that control often deteriorates in adolescents and young adults. They suggest that this technology has potential to enhance management of type 1 diabetes in sufficiently motivated adults.