Butala NM, Johnson BK, Dziura JD, Reynolds JS, Balcezak TJ, Inzucchi SE, Horwitz LI. Decade-Long Trends in Mortality Among Patients With and Without Diabetes Mellitus at a Major Academic Medical Center. JAMA Intern Med. 2014;174(7):1187-1188. doi:10.1001/jamainternmed.2014.1803
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The prevalence of diabetes mellitus has risen markedly over the past decade and is projected to increase substantially.1 More than 20% of hospitalized patients are estimated to have diabetes,2 and individuals with diabetes have historically experienced higher inpatient mortality than individuals without diabetes.3 Over the past decade, evidence from large clinical trials has prompted recommendations for tighter inpatient and outpatient glucose control, as well as more stringent blood pressure and lipid management, to improve outcomes for patients with diabetes.4- 6 It is unclear whether the mortality impact of diabetes has changed as a consequence.
We examined 11-year trends in mortality among patients with and without diabetes hospitalized at Yale–New Haven Hospital, a major urban medical center. We obtained approval from the Yale Human Research Protection Program, which provided a waiver of informed consent. We considered all adult, nonobstetric patients with an inpatient discharge between January 1, 2000, and December 31, 2010, in Yale–New Haven Hospital administrative billing data. The primary end point was in-hospital mortality. Diabetes status was defined as a diagnosis of diabetes during the index admission or in any hospital encounter in the year prior to the index admission. Time was measured as the difference between January 1, 2000, and patient admission date, in years. We additionally included an array of covariates based on established associations with in-hospital mortality.
We used a difference-in-differences approach comparing changes over time in in-hospital mortality in patients with vs without diabetes to determine whether patients with diabetes had a different time trend in risk of in-hospital mortality. We constructed multivariate logistic regression models including time in years, diabetes status, and the interaction between time and diabetes status, as well as an array of covariates. We calculated odds of death and confidence intervals for each additional year for patients with diabetes by exponentiating the sum of parameter estimates for time and the diabetes-time interaction term. We used a type I error of 5% (2-sided) to test for statistical significance and obtained point estimates and 95% confidence intervals via the bootstrap method.
We included 322 938 hospitalizations, of which 76 758 (23.8%) were from patients with diabetes. The overall mortality rate was 2.3%: 2.7% of patients with diabetes and 2.2% of patients without diabetes. Unadjusted mortality among patients with diabetes decreased from 3.6% in 2000 to 2.2% in 2010 while mortality among patients without diabetes decreased from 2.4% in 2000 to 2.3% in 2010. The Figure shows quarterly in-hospital mortality for patients with and without diabetes from 2000 to 2010.
The Table describes the difference-in-differences regression analyses. Each successive year was associated with a 4.5% reduction in the adjusted odds of mortality (odds ratio [OR], 0.96 [95% CI, 0.95-0.96]) for patients without diabetes compared with an 8.7% reduction for those with diabetes (OR, 0.91 [95% CI, 0.90-0.93]). Patients with diabetes compared with patients without diabetes had a significantly greater decline in risk of adjusted mortality of 4.4% per year (OR, 0.96 [95% CI, 0.94-0.97]). The adjusted odds of mortality among patients with vs without diabetes decreased from 1.20 in 2000 to 0.78 in 2010.
In a decade with increasing emphasis and accountability for glycemic control and cardiovascular risk management among patients with diabetes, we found that patients with diabetes have experienced a disproportionate reduction in in-hospital mortality over time and a complete reversal in risk of mortality relative to patients without diabetes. This interesting trend warrants additional study to elucidate its origins. Potential explanations include coincident improvements in inpatient glycemic control, improvements in outpatient glycemic control, improved nonglycemic cardiovascular risk management among patients with diabetes, and/or advances in therapies for diseases that disproportionately affect patients with diabetes.
Corresponding Author: Leora I. Horwitz, MD, MHS, Section of General Internal Medicine, Department of Medicine, Yale School of Medicine, PO Box 208093, New Haven, CT 06520-8093 (email@example.com).
Published Online: May 19, 2014. doi:10.1001/jamainternmed.2014.1803.
Author Contributions: Dr Horwitz had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Butala, Balcezak, Horwitz.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Butala, Dziura, Reynolds, Horwitz.
Critical revision of the manuscript for important intellectual content: Butala, Johnson, Dziura, Reynolds, Balcezak, Inzucchi.
Statistical analysis: Johnson, Dziura, Reynolds, Horwitz.
Obtained funding: Horwitz.
Administrative, technical, or material support: Butala, Balcezak, Horwitz.
Study supervision: Balcezak, Inzucchi, Horwitz.
Conflict of Interest Disclosures: Dr Inzucchi serves on a Data Safety Monitoring Board for Novo Nordisk, a manufacturer of insulin products used in the hospital setting. No other disclosures are reported.
Funding/Support: Dr Horwitz is supported by the National Institute on Aging (K08 AG038336) and by the American Federation for Aging Research through the Paul B. Beeson Career Development Award Program.
Role of the Sponsors: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: The authors thank the Yale–New Haven Hospital diabetes management team: Gael Ulisse, APRN, Helen Psarakis, APRN, Anne Kaisen, APRN, and the Yale Endocrine Fellows, for providing high-quality clinical care to the patients in this study, and Janis Bozzo, MSN, RN, Decision Support, Yale–New Haven Health System, for assistance in obtaining study data. None of these individuals received compensation for their contribution.