The challenge of assessing impaired awareness of hypoglycaemia in diabetes in the era of continuous glucose monitoring: a narrative review of evidence and translation into clinical practice.

Iatrogenic hypoglycaemia remains a major barrier in diabetes care. Over time, and with repeated hypoglycaemic episodes, the physiological responses to hypoglycaemia can become blunted, resulting in impaired awareness of hypoglycaemia (IAH). In IAH, the onset of cognitive dysfunction precedes the onset of autonomic symptoms, often preventing appropriate self-treatment, thus increasing the frequency of severe hypoglycaemia (SH). Historically, IAH has been assessed with questionnaires, such as the Gold and Clarke scores, which were developed in the 1990s. A stepwise change in diabetes management in the last few decades has been the deployment of continuous glucose monitoring (CGM). CGM allows people with diabetes to set alarms that can warn them of hypoglycaemia or even impending hypoglycaemia, thus providing a degree of 'technological' awareness. This creates a challenge in assessing awareness status, as people may be alerted to low-sensor glucose events before they experience any symptoms. CGM also allows the introduction of new measures of hypoglycaemia exposure such as time below range, which might complement traditional methods of risk assessment. These changes in the field prompt a need for reassessment of the measures of IAH. This narrative review evaluates the current epidemiology of SH and IAH, explores different measures of IAH, and evaluates the relationship between CGM metrics, IAH and SH. We conclude that a clinical approach involving traditional questionnaires, or newer updated alternatives such as the Hypo A-Q awareness scale, combined with CGM metrics and clinical assessment of human factors is recommended in the absence of a clearly superior measure.