Aims: Impaired awareness of hypoglycaemia (IAH) is thought to affect approximately 25% of people with Type 1 diabetes. While this estimate was based on retrospective information from patients in several small studies performed several years ago, validated methods of assessment have not been used in a large hospital clinic-based population to ascertain the prevalence in the present era.
Methods: Five hundred and eighteen people with Type 1 diabetes were recruited by random selection over a 2-year period. Participants completed a questionnaire documenting baseline characteristics and assessment of their awareness status using the method described by Gold et al. The number of episodes of severe hypoglycaemia they had experienced in the preceding year was recorded retrospectively.
Results: IAH was present in 19.5% of the cohort. Compared to those with normal awareness of hypoglycaemia, those with IAH were significantly older [mean +/- standard deviation (sd); 39.3 +/- 12.9 vs. 45.9 +/- 13.5 years, P < 0.001], had a longer duration of diabetes [median (interquartile range) 14 (8-22) vs. 23 (14-32) years, P < 0.001], and had a six-fold higher frequency of severe hypoglycaemia in the previous year [0.38 +/- 1.04 (25th-75th centile 0-0) vs. 2.36 +/- 4.81 (25th-75th centile 0-2) episodes per person, P < 0.001].
Conclusions: The present survey of a large hospital-based clinic population has confirmed that a significant proportion of people with Type 1 diabetes (19.5%) continue to have IAH. Despite improvements in insulin therapies, intensification of insulin regimens and innovative patient education, the prevalence of IAH remains high in Type 1 diabetes.