Although diabetes is known to be a risk factor for heart failure, surprising new Australian findings show it is associated with lower mortality rates in patients hospitalised for heart failure.
A review of 1191 patients admitted with decompensated heart failure at Austin Health, Victoria, between 2013 and 2015 found that half the patients (49%) had diabetes (HbA1c >6.5%) and 34% had prediabetes (HbA1c 5.7-6.4%).
However, contrary to the researchers’ hypothesis, diabetes was associated with a significantly lower six–month mortality (16.4%) compared to HF patients with no diabetes (29.2%).
And even after adjusting for other variables there was also no effect of diabetes on other hospital outcomes such as ICU admission, length of stay and 28-day readmission rates.
The study authors, led by Dr Elif Ekinci and Dr Kalyn Khoo of the Department of Endocrinology at Austin Health, noted that the patients with diabetes were more likely to be on evidence based cardiac preventive medications such as ACE inhibitor or ARB (61% vs 52%), beta blockers (67% vs 55%) and statins (70% vs 44%) than patients with no diabetes.
In addition, patients with diabetes were more likely to be on an aldosterone antagonist on admission.
“The current study findings are likely to be related to the fact that those with diabetes were more likely to be on evidence-based treatment on admission – that is beta blockers, renin-angiotensin blockade and statins, as well as aldosterone antagonists, which have all been demonstrated to have a mortality benefit,” they wrote.
“Drugs that prevent cardiac remodelling, such as renin-angiotensin system antagonists, may also modulate the severity of heart failure and its consequences.”
However they noted that the study was done before the era of widespread use of diabetes drugs with cardioprotective effects such as DPP-4 inhibitors and SGLT-2 inhibitors.
They also noted that patients with diabetes were morel likely to have diastolic rather than systolic dysfunction.
Other possible explanations include the obesity paradox, but this could not be explored because of the lack of BMI data, they suggested.
The study is published in Nature Scientific Reports.