HYPOGLYCEMIA INCREASES MI RISK

October 5, 2009 (Vienna, Austria) — A new case-control study has shown that an episode of hypoglycemia in diabetes patients is associated with a higher risk of MI for the following two weeks and possibly for a few months afterward. Dr Donald R Miller (Boston University School of Public Health, MA) reported the findings at the European Association for the Study of Diabetes (EASD) 2009 Meeting last week.

"We found an increased risk [of MI] in the short term from hypoglycemia, and there's a hint of long-term increased risk--those were the two questions we addressed," Miller told heartwire . However, he added, "I'd say the long-term risk is very small and may not be there, because it's certainly within the range of controlled confounding."

He and his colleagues say further and more detailed studies are needed to better measure the risks and identify conditions whereby hypoglycemia may lead to MI. These risks, they add, should be taken into account by doctors during the management of diabetes, with appropriate choice of therapies and treatment goals to minimize the likelihood of hypoglycemia occurring.

Risk of MI Increased 65% Within Two Weeks of Hypoglycemic Episode

Miller said he had been interested in whether hypoglycemia could precipitate cardiovascular disease events for a number of years, but it "really was ignited by the [Action to Control Cardiovascular Risk in Diabetes] ACCORD and then the [Veterans Affairs Diabetes Trial] VADT results that highlight the risks that may be there."

The ACCORD study was halted prematurely last year because of an increased risk of death in diabetes patients who underwent intensive blood glucose lowering. And VADT showed that intensive blood glucose lowering had no significant effect on the rates of cardiovascular events, death, or microvascular complications. In addition, the Action in Diabetes and Vascular Disease (ADVANCE) trial showed a reduction in the progression of albuminuria with intensive glucose control but no effect on cardiovascular-event rates.

Miller and colleagues thus set out to examine whether hypoglycemia is a precipitating factor for MI, and if so, by how much it might increase the risk within a short period of time. They also looked at whether predisposition for or history of hypoglycemia is associated with a higher risk of MI.

Using data from the Diabetes Epidemiology Cohorts of the Veterans Affairs (VA) system, they looked at the medical records of all VA patients with diabetes from 2000 to 2004 who had had at least two years of VA care and no prior MI, acute coronary syndrome, or cardiac surgery. Hypoglycemia was confirmed from medical records at any encounter, whether it was outpatient clinic, emergency room, or in an inpatient setting. Cases were defined as the first hospital MI, and controls were chosen by random selection.

They found a 65% increased odds of MI associated with hypoglycemia within the previous two weeks, even after adjustment for potential confounding factors. And a lower, but still slightly elevated, risk of MI, of around 20%, was seen for hypoglycemia events within the previous six months.

Miller and colleagues found only small differences relating to insulin use compared with no insulin use and a slightly higher risk of MI associated with inpatient hypoglycemia compared with hypoglycemia recorded in other settings. They also found a small 10% increased risk of MI for hypoglycemia in the more distant past.

Risk of MI Associated With Episode of Hypoglycemia Within a Given Prior Period

Any hypoglycemia in specific periods	Cases (%)	Controls (%)	Adjusted risk of MI (95% CI)
Index date or day before	2.9	0.1	--
Prior 2 wk	1.1	0.3	1.65 (1.50–1.81)
Previous 5.5 mo	6.0	2.5	1.20 (1.15–1.25)
Previous 6 mo	4.8	2.1	1.11 (1.06–1.15)
Previous y	9.6	4.2	1.12 (1.08–1.16)

Pay attention to treatments that may increase the risk of hypoglycemia, because it has risks that have not been recognized up to this point.

Miller told heartwire : "My message is: pay attention to treatments that may increase the risk of hypoglycemia, because it has risks that have not been recognized up to this point and should be considered in the balance of risks/benefits for diabetes therapies." Tailoring therapy to the individual is the best approach, he concluded.

There was much debate at the EASD meeting last week on what the ideal glycated hemoglobin A_1c (HbA_1c) goal should be, and this subject will be covered in more detail in a future report on heartwire .