Aims/hypothesis: As glycaemia and the incidence of microvascular diabetes complications follow a log-linear relationship, it becomes increasingly difficult to demonstrate a microvascular benefit of glucose-lowering when the HbA1c level is close to normal.
Methods: The Outcome Reduction with an Initial Glargine Intervention (ORIGIN) trial randomised 12,537 people with diabetes, impaired glucose tolerance or impaired fasting glucose to receive standard glycaemic care or standard care with the addition of basal insulin glargine (A21Gly,B31Arg,B32Arg human insulin), targeting a fasting plasma glucose level ≤5.3 mmol/l. Microvascular outcomes during a median follow-up of 6.2 years were examined in participants whose baseline HbA1c was above or below the median of 6.4% (46.4 mmol/mol).
Results: Allocation to the insulin glargine group reduced the incidence of the primary microvascular composite outcome of kidney and eye disease in participants whose baseline HbA1c level was ≥6.4% (46.4 mmol/mol; HR 0.90 [95% CI 0.81, 0.99]) but not in participants with a lower baseline HbA1c (HR 1.07 [95% CI 0.95, 1.20]; p value for interaction 0.031). In people whose baseline HbA1c level was ≥6.4% (46.4 mmol/mol), the median post-randomisation change in HbA1c was -0.65% (interquartile range -0.16, -0.91%) after allocation to insulin glargine and -0.33% (-0.83, 0.13%) after allocation to standard care (median HbA1c difference 0.33%; p < 0.0001). A smaller median difference of 0.22% was noted in people whose baseline HbA1c was <6.4% (p < 0.0001).
Conclusions/interpretation: In patients with dysglycaemia, intervention targeting normal fasting glucose levels reduced HbA1c and attenuated the risk of microvascular outcomes in participants with a baseline HbA1c level ≥6.4% (46.4 mmol/mol). A neutral effect was seen in those with a lower baseline HbA1c level.
Trial registration: ClinicalTrials.gov NCT00069784.