Temporal changes in glycaemic thresholds for treatment intensification in type 2 diabetes in an urban Australian setting: the Fremantle Diabetes Study

Background: Pharmacotherapy and supportive care for diabetes in Australia are improving, with potential beneficial effects on therapeutic procrastination. Aim: To determine whether glycaemic thresholds for therapeutic intensification in type 2 diabetes changed over the 15 years between phases of the community-based Fremantle Diabetes Study (FDS). Methods: We studied 531 Phase 1 participants (mean age 62.4 years, 54.2% males, median diabetes duration 3.0 years) with valid data from baseline assessment and five subsequent annual reviews between 1993 and 2001 and 930 Phase 2 participants (mean age 65.3 years, 53.8% males, median diabetes duration 8.0 years) with valid data from baseline and two subsequent biennial reviews between 2008 and 2015. The main outcome measure was HbA_1c at assessments before and after change in blood glucose-lowering therapy (average 6 months in Phase 1, 12 months in Phase 2). Results: Ninety-seven participants in Phase 1 and 84 in Phase 2 progressed from diet-based management to oral hypoglycaemic agents (OHA) and 45 and 85 participants, respectively, progressed from diet/OHA to insulin. The median HbA_1c was 7.5% (58 mmol/mol) and 6.9% (52 mmol/mol) before OHA initiation in Phases 1 and 2, respectively, and 9.1% (76 mmol/mol) and 7.8% (62 mmol/mol), respectively, before insulin initiation. There were median HbA_1c falls of 0.3% (3 mmol/mol) and 1.5% (16 mmol/mol) after OHA and insulin initiation in Phase 1, but no statistically significant changes in Phase 2. Conclusions: HbA_1c thresholds triggering treatment intensification fell between FDS phases, suggesting a more proactive approach to management of glycaemia over time.