Incremental Burden of Type 2 Diabetes Mellitus in Patients Experiencing Cardiovascular Hospitalizations

Study conducted by: Coutinho AD, Raju A, Wang W, et al.

Background

  • Cardiovascular disease (CVD) is associated with significant morbidity and mortality, with inpatient CV hospitalizations accounting for 43% of the total economic burden of CVD.1,2
  • Patients with type 2 diabetes mellitus (T2DM) have a 2‑fold higher risk of having a cardiovascular (CV) hospitalization compared to those without T2DM.3
  • It is unclear if T2DM continues to increase the risk of subsequent hospitalization and economic burden following discharge from a CV hospitalization.

Study Objective

  • To evaluate the incremental economic burden of T2DM in patients experiencing CV hospitalizations.

Methods

Data Source and Study Design

  • IMS LifeLink PharMetrics Plus Claims Database
  • A retrospective cohort design was employed to assess the study objectives.
Methodology for study regarding incremental burden of type 2 diabetes mellitus in patients experiencing cardiovascular hospitalizations

Retrospective Cohort Study Design

Study Criteria

  • Inclusion:
    • Patients with CV hospitalizations, defined as having a primary discharge diagnosis for acute myocardial infarction (MI), unstable angina, stroke, heart failure (HF), cardiac arrest, arrhythmia, or other primary diagnosis with a revascularization procedure
    • ≥18 years of age
    • Continuous health plan enrollment during the pre‑index period
  • Exclusion:
    • Diagnosis of pregnancy, gestational diabetes, secondary diabetes, or type 1 diabetes mellitus anytime during the pre- or post‑index period
    • Missing demographic information (age, gender, geographic region)

Exposure Definition

  • T2DM status: identified during the pre‑index period, and defined as having:
    • ≥1 hospitalization with a diagnosis of T2DM in any diagnosis field OR
    • ≥ 2 medical claims at least 30 days apart within 12 months in the outpatient setting, except lab and radiology, with a diagnosis of T2DM in any diagnosis field OR
    • ≥1 pharmacy claim indicated for T2DM, including a) a non‑insulin injectable, or b) an oral anti‑diabetic agent, except metformin, or c) metformin pharmacy claim without a diagnosis code for pre‑diabetes or polycystic ovary syndrome4

Study Outcomes

  • All patients were included for analysis of outcomes from the index CV hospitalization, but only those surviving the index CV hospitalization were analyzed for outcomes during the post‑discharge period.
  • Risk of subsequent CV hospitalizations
  • Healthcare resource use:
    • All‑cause and CVD‑related length of stay per hospitalization, and bed‑days per patient
    • Number of all‑cause and CVD‑related visits by setting of care (reported per patient per month)
  • Healthcare costs in 2015 United States dollars (USD)
    • All‑cause and CVD‑related costs (reported per patient per month) were computed using paid amounts on claims.

Statistical Analysis

  • Baseline characteristics: t‑tests and chi‑square tests
  • Risk of subsequent CV hospitalizations: Cox proportional hazards models
  • Costs and resource use: generalized linear models with outcome‑appropriate distributions
  • All outcomes were assessed for T2DM vs non‑T2DM patients; and multivariate models for all outcomes controlled for the following covariates measured during the pre‑index period: age; gender; region; payer and plan type; index year; revascularization procedure; HF, MI, or stroke events; type of CVD condition; Charlson comorbidity index; and other CVD risk factors.
  • Statistical analyses were conducted using SAS® version 9.2 (SAS Institute; Cary, NC, USA).
Additional information can be found by downloading the full poster.

References: 1. Mozaffarian D, Benjamin EJ, Go AS, et al. Heart disease and stroke statistics—2016 update: a report from the American Heart Association. Circulation. 2016;133(4):e38‑e360. 2. Nichols GA, Bell TJ, Pedula KL, O’Keeffe‑Rosetti M. Medical care costs among patients with established cardiovascular disease. Am J Manag Care. 2010;16(3):e86‑e93. 3. Roche MM, Wang PP. Sex differences in all‑cause and cardiovascular mortality, hospitalization for individuals with and without diabetes, and patients with diabetes diagnosed early and late. Diabetes Care. 2013;36(9):2582‑2590. 4. Solberg LI, Engebretson KI, Sperl‑Hillen JM, et al. Are claims data accurate enough to identify patients for performance measures or quality improvement? The case of diabetes, heart disease, and depression. Am J Med Qual. 2006;21(4):238‑245.

Sample Characteristics

  • 316,207 patients met the study criteria, 23% of whom had T2DM.
  • T2DM cohort was older and had a higher comorbidity burden vs non‑T2DM cohort.
  • T2DM patients had a higher number of CV disease conditions, with atherosclerosis/ischemic heart disease, arrhythmias, HF, MI, and stroke being most prevalent.
  • 1.7% of the patients died during the index CV hospitalization (the same proportion in both cohorts); hence post‑discharge outcomes were assessed among the remaining 310,926 patients.

Study Outcomes

  • T2DM patients had 19% statistically significant higher risk of subsequent CV hospitalizations
Adjusted Survival Curve of Risk of Subsequent CV Hospitalization

Adjusted Survival Curve of Risk of Subsequent CV Hospitalization

  • T2DM patients had a significantly higher length of stay at index CV hospitalization and during subsequent hospitalizations.
    • The mean number of bed-days was also higher among T2DM patients.*
Adjusted Mean Length of Stay and Bed-days

Adjusted Mean Length of Stay and Bed-days

*Additional information can be found by downloading the full poster
All comparisons between cohorts are significant at P<0.001
  • Adjusted costs of index CV hospitalization and costs during the post-discharge period were significantly higher for patients with T2DM vs non‑T2DM patients.
Chart comparing cost of hospitalization and discharge for patients with type 2 diabetes vs. patients without.

Adjusted Costs During Index Hospitalization and Post‑discharge

*All comparisons between cohorts are significant at P<0.001
T2DM patients (N=71,237)
Non‑T2DM patients (N=244,970)
Please see the poster for demographic data.

Conclusion

  • Among patients experiencing CV events, comorbid T2DM was associated with an increased risk of subsequent CV hospitalizations, along with higher all‑cause and CVD‑related resource use and costs.
Additional information can be found by downloading the full poster.

Limitations

  • Results may be confounded by missing some important CV risk factors, such as smoking status and obesity.
  • Since this study had variable follow‑up time and censored patients in the event of death, disenrollment, or the end of available data, complete cost data were not available for all patients for estimating total healthcare resource utilization and costs between cohorts.
  • Results of the analysis are primarily generalizable to a commercially insured population, which make up approximately 90% of the sample.
Additional information can be found by downloading the full poster.