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Abstract
Heart failure (HF) patients are at risk of new-onset type 2 diabetes because of heightened insulin resistance resulting from compensatory mechanisms of cardiac dysfunction. Patients with coexisting HF and diabetes face increased risks of morbidity and mortality in comparison to patients with HF alone which makes the early identification and management of type 2 diabetes among HF patients important. The objectives of this dissertation were to 1) assess prevalence and trends of type 2 diabetes and prediabetes among HF patients in the U.S. (study 1, chapter 3), to 2) compare diagnostic methods for type 2 diabetes among HF patients in the U.S. (study 2, chapter 4), and to 3) examine the association between the Dietary Approaches to Stop Hypertension (DASH) diet adherence and insulin resistance among HF patients in the U.S. (study 3, chapter 5). In study 1, more than 85% of HF patients showed signs of hyperglycemia: prevalence estimates of diagnosed, undiagnosed type 2 diabetes, and prediabetes among HF patients were 34.7%, 12.8%, and 39.1%, respectively. Prevalence estimates of diagnosed type 2 diabetes were significantly different between non-Hispanic whites (20.1% [95% CI, 13.5- 27.6%]) and Hispanics (52.1% [95% CI, 35.9-68.0%]) (P < 0.001). The prevalence of type 2 diabetes and prediabetes did not significantly change between 2005 and 2016. In study 2, we found the concordance in diabetes case detection among diagnostic methods for diabetes to be limited: hemoglobin A1c (HbA1c) alone identified only 27.0%, whereas the 2-hour plasma glucose after oral glucose tolerance test alone identified 70.5% of cases. We found that the currently recommended HbA1c cutoff point of 6.5% would have left 76% of diabetes cases in our sample undiagnosed. In study 3, we observed that HF patients with the highest DASH adherence, in comparison to those with the lowest DASH adherence, showed 77.1% lower odds of having the highest level of insulin resistance (odds ratio: 0.229 [95% CI: 0.073-0.716]; p = 0.017 for linear trend). In conclusion, emphasis needs to be placed on the prevention and early diagnosis of new-onset type 2 diabetes among HF patients to reduce the individual and societal burden.