Impaired awareness of hypoglycaemia (IAH) is a common, frustrating, and potentially dangerous problem for people with diabetes who use insulin. While researchers have yet to unravel the physiological underpinnings of IAH, neuroimaging studies have shed light on how the brain responds to hypoglycaemia—and how these responses may change as IAH sets in.
An awareness of hunger prompts people to open the refrigerator. The same process alows people to limit the damage of hypoglycaemia: a mental awareness of symptoms gives people a chance to take corrective action.
Hypoglycaemia affects not only people with diabetes, but everyone who loves and cares for them. Having a brother with type 1 diabetes, I have seen this phenomenon up close. My brother would sometimes drive to unfamiliar places without remembering how he got there. He would awaken at night, confused and belligerent. On several occasions, a family member had to call emergency medical services to treat him. Over time, these episodes created a chronic weariness and wariness in our family, which persisted even after a continuous glucose monitoring (CGM) system significantly reduced his lows. Having a sister who knows quite a lot about hypoglycaemia has not fully solved his challenges with hypoglycaemia.
Many clinicians perceive the risk of severe hypoglycaemia as firmly tethered to the level of glucose control: the tighter the control, the greater the risk. This perception has its roots in the historical association between A1C and hypoglycaemia risk, established in several studies. As a frequently cited example, the DCCT trial found a 3-fold increased risk of severe hypoglycaemia in patients randomized to the intensive management arm of the study.
Optimizing glucose control is critical for patients with diabetes to minimize risks of micro- and macrovascular complications associated with hyperglycaemia. To this end, individuals with diabetes who depend on insulin replacement therapy, particularly those on basal-bolus regimens, need to be aware of their blood glucose values to guide treatment decisions.
There is a line in the sand between mild and severe hypoglycaemia (SH). While mild hypoglycaemia is not trivial, it does not threaten life and health as SH does. For people who depend on insulin and other glucose-lowering drugs associated with hypoglycaemia, clinicians often consider a degree of SH “the cost of doing business” in diabetes management—in other words, an unwanted but unavoidable corollary of treatment.
Iatrogenic hypoglycaemia is the limiting factor in the glycaemic management of diabetes, particularly with insulin. That hypoglycaemia can kill experimental animals has been known since the discovery of insulin. There are now numerous reports of deaths of patients with diabetes associated with hypoglycaemia. Since hypoglycaemia can kill, and hypoglycaemia at the time of death has been documented by continuous glucose monitoring in a patient with diabetes, it is reasonable to conclude that these are causal associations.