To identify patient clusters with poor glucose control among type 2 diabetes mellitus (T2DM) patients with obesity who are receiving basal-bolus insulin and to identify the potential therapeutic inertia factors associated with poor control.


Glycated haemoglobin (HbA1c) trajectories across a 3-year period were structured at 6-month intervals for a retrospective cohort of T2DM patients with obesity on basal-bolus insulin from the Veterans’ Health Administration database. Based on each patient’s longitudinal HbA1c features, an unsupervised clustering procedure was used to determine the numbers of clusters and associated trajectory patterns. Multinomial logistic regression was used to examine the association between HbA1c trajectory clusters and patient characteristics/treatment patterns.


A total of 51 273 patients were included, of whom 11.2% were in a subgroup with persistent missingness of HbA1c values. For those with sufficient HbA1c observations, cluster analysis indicated six distinct HbA1c trajectories: stable low (35.8%); stable high (20.8%); descending low (10.5%); ascending low (10.2%); descending high (5.7%); and ascending high (5.7%). Being of Black ethnicity, not initiating noninsulin antihyperglycaemic agents (sodium-glucose cotransporter-2 inhibitors, glucagon-like peptide-1 receptor agonists or thiazolidinediones) or concentrated insulin, low adherence (measured by proportion of days covered), and reduced insulin prescription refills were factors associated with poorer HbA1c clusters; similar factors were associated with persistent HbA1c missingness.


The present study found the potential for therapeutic inertia among a significant proportion of T2DM patients with obesity on basal-bolus insulin. Subgrouping T2DM patients based on HbA1c missingness and HbA1c trajectories can inform disease management strategies.

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