A register-based study describing time trends in risk factor control and serious hypoglycaemia together with the effects of starting continuous glucose monitoring in people with type 1 diabetes in Norway.

Aims: To describe trends in risk factor control and serious hypoglycaemia in people with type 1 diabetes and to assess the effect of starting continuous glucose monitoring (CGM) in the real-world setting.

Methods: Two cross-sectional surveys including 5746 individuals in 2012 and 18,984 individuals in 2020 based on data recorded in the Norwegian Diabetes Register for Adults (NDR-A) and an analysis of a longitudinal cohort of 2057 individuals where data on CGM and HbA1c were available in the NDR-A in 2012 and 2020.

Results: In the cross-sectional surveys mean HbA1c decreased from 66 mmol/mol (99% CI 65, 66) (8.2%) in 2012 to 61 mmol/mol (99% CI 61, 61) (7.7%) in 2020 (p < 0.0001). The proportion reporting serious hypoglycaemia decreased from 16.9 to 6.2% in 2020 (p < 0.0001). Mean LDL-cholesterol decreased from 2.80 (99% CI 2.78, 2.83) to 2.63 (99% CI 2.61, 2.65) mmol/l in 2020 (p < 0.0001). Mean blood pressure increased slightly. In the CGM cohort, we found a 3 mmol/mol (0.3%) greater improvement in mean HbA1c and a greater reduction in serious hypoglycaemia (-12.3% vs. -6.2%) among individuals that had started using CGM between 2013 and 2020 when compared with individuals that had not started using CGM.

Conclusions: Between 2012 and 2020, we found marked improvements in glycaemic control and a considerable decrease in the proportion of individuals reporting serious hypoglycaemia. The proportion of individuals using CGM increased substantially and individuals that had started using CGM by 2020 showed greater improvement in glycaemic control and less serious hypoglycaemia.