Asymptomatic Hypoglycemia, a Silent Killer

After 26 years of marriage to someone with Type 1 diabetes, Roberta Rabinek has grown to learn when her husband, George, is having a hypoglycemic attack, even if he can’t tell it’s happening.

“He’ll tell me he’s fine and to leave him alone,” says Rabinek, who lives in Baltimore. “But he will be a little off…repeats himself a lot and is less responsive. That’s when I know, even if he doesn’t, and make him test his blood sugar. 9 times out of 10 I’m right.”

Asymptomatic hypoglycemia can be like a boogeyman under the bed for people with diabetes. It’s that scary in-between when those with Type 1 have a low blood sugar without necessarily feeling like they’re in trouble. Clinically, a bout of asymptomatic hypoglycemia involves a measured plasma glucose below ≤70 mg/dL (≤3.9 mmol/L), not accompanied by some or all of the typical symptoms of hypoglycemia. While usually mild, asymptomatic hypos are having an effect and taking a toll on the body. There’s even strong evidence that silent hypos can lead to more hypos, both silent and severe.

How often does asymptomatic hypoglycemia strike? It’s hard to say, but most likely it’s probably more often than you think. A 2011 Catalina Research Institute study on continuous glucose monitoring found that 60% of all people with diabetes experience unrecognized hypoglycemia, with most of these silent incidents happening at night. But still researchers are largely in the dark about how often asymptomatic hypoglycemia strikes, because patients usually can’t, or don’t think to, report it.

According to Dr. Jing Wang, an assistant professor with the department of nursing systems at the University of Texas Health Science Center, asymptomatic hypoglycemia, like other forms of hypoglycemia, can occur because of any combination of too much insulin in the bloodstream, excess stress, or skipping a meal. It’s most likely to occur in the first 14 weeks after initiating insulin therapy or after one’s insulin therapy has been adjusted.

Perversely, silent hypoglycemia tends to create a vicious cycle. Repeated exposures to hypoglycemia can rewire the brain to make it less sensitive to future lows, says Dr. Leann Olansky, an endocrinologist at the Cleveland Clinic. The more wear and tear on the neurons because of asymptomatic or symptomatic hypoglycemia, the less likely the brain will be able to detect a low over time.

“The brain tends to desensitize to one’s low blood glucose and stops sending out the hormonal signals that let the person suspect that his or her blood glucose is dropping,” Dr. Olansky says.

stk79785corIt’s hard to quantify the effects of silent hypoglycemic attacks because they fly under the radar, but experts agree that marriages have been broken up because of them, careers have been ruined by them, and they definitely put a dent in the pocketbook. One 2007 Canadian Journal of Diabetes study estimated that 13% of all out-of-pocket expenses for diabetes comes as a result of “non-severe” bouts of hypoglycemia, including silent hypoglycemia.

One reason more is not known about asymptomatic hypoglycemia is that it isn’t being well-documented by primary care physicians, who often don’t think to ask about it. According to a 2012 Catalina Research Institute review of studies on asymptomatic hypoglycemia, people with diabetes aren’t getting the prompting needed from physicians to discuss or track their silent lows. The review’s author, Dr. Jeff Unger, believes it’s vital for primary care physicians to educate themselves on hypoglycemia and ask patients on insulin therapy about lows every time they visit.

“Primary care physicians play a key role in the prevention and management of hypoglycemia in patients with diabetes, particularly in those requiring intensive insulin therapy, yet physicians are often unaware of the multitude of consequences of hypoglycemia or how to deal with them,” Dr. Unger writes.

While asymptomatic hypoglycemia can be scary, bouts can be curbed and prevented. Blood glucose monitoring is key; testing is the only way to know if you’re having an attack. Even if you can still feel a low, testing can help you catch hypoglycemia before it gets out of hand. And cutting off hypos before they start or get too severe keeps your brain on guard for future bouts of hypoglycemia. One of the first recommendations for people with diabetes who are unaware of their lows is meticulous testing for a 3-week period.

In the last decade, diabetes gear has vastly improved to cut down on bouts of hypoglycemia, silent or otherwise. If you’re looking to head off silent lows, there are options available. Continuous glucose monitoring (CGM) devices have been well documented to cut down on lows. In one 2011 Juvenile Diabetes Research Foundation study, patients who used CGMs saw their incidents of hypoglycemia drop from 21.8 to 7.1 per year. Insulin pumps also are proven to cut down on all types of hypoglycemia and improve glucose control. Recently, Medtronic has unveiled a pump that automatically suspends insulin delivery for 2 hours if it detects blood glucose levels dipping too low (see “Medtronic’s ‘Artificial Pancreas’ Gains FDA Approval”). People with diabetes who use such “smart pumps” can experience 4 times fewer bouts of hypoglycemia than people using regular pumps, according to a recent study by Australian researchers. Even traditional pump users experience 6 times fewer hypos compared to those using traditional injectable insulin alone, the study suggests (see “Study: Smart Pumps Prevent Hypos”).

It’s also important to discuss asymptomatic or symptomatic hypoglycemia every visit with one’s health care provider, experts agree. Make sure you’re with a health care provider who is comfortable discussing the ins and outs of hypoglycemia, especially if he or she is recommending that you make any changes in your insulin therapy or any other diabetes-related medication.

Ultimately, while it feels like asymptomatic hypoglycemia is another one of those terrible things that just “happens” to a person with diabetes, there is a lot one can do to take control, says Dr. Carolyn Dean, a noted nutritionist and author. Dr. Dean says that while new diabetes gear may help better control blood glucose, preventing and controlling hypoglycemia depends largely on the steps taken by a person with diabetes and his or her support team.

“An organized approach to your diabetes will allow you to lead a healthy life,” she stresses.

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Jeanne Muchnick is a freelance writer who specializes in health and lifestyle issues for a variety of print and online venues.

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