A Real-World Study of the Effect of Timing of Insulin Initiation on Outcomes in Older Medicare Beneficiaries with Type 2 Diabetes Mellitus

ObjectivesTo compare clinical and economic outcomes of early insulin initiation with those of delayed initiation in older adults with type 2 diabetes mellitus (T2DM). DesignRetrospective cohort study. SettingHumana Medicare Advantage health insurance plan. ParticipantsOlder (65) Medicare beneficiaries with T2DM. MeasurementsSubjects were grouped according to number of classes of oral antidiabetes drugs (OADs) they had taken before initiation of insulin: one (early insulin initiators), two, or three or more (delayed insulin initiators). One-year follow-up outcomes included change in glycosylated hemoglobin (HbA1c), percentage of older adults with HbA1c less than 8.0%, hypoglycemic events, and total healthcare costs. ResultsOverall, 14,669 individuals were included in the analysis. Baseline and 1-year follow-up HbA1c levels were available for 4,028 (27.5%) individuals. Insulin was initiated early in 32% and delayed in 20%. At follow-up, unadjusted reduction in HbA1c was 0.93.7% for the group with one OAD, 0.7 +/- 2.4% for those with two, and 0.5 +/- 3.6% for those with three or more. Early insulin initiation was associated with significantly greater reduction in HbA1c (0.4%; adjusted P<.001), 30% greater likelihood of achieving HbA1c less than 8.0% (adjusted odds ratio=1.30, 95% confidence interval=1.18-1.43), and no significant differences in total costs or hypoglycemia events (11.5% of early initiators vs 10.2% of delayed initiators; P=.32). ConclusionThis study suggests beneficial effects of early insulin initiation in older adults with T2DM who do not have adequate glycemic control, without increasing the risk of hypoglycemia or greater total direct healthcare costs.