The effects of acute hypoglycaemia on memory acquisition and recall and prospective memory in type 1 diabetes.
OBJECTIVE
Global memory performance is impaired during acute hypoglycaemia. This study assessed whether moderate hypoglycaemia disrupts learning and recall in isolation, and utilised a novel test of prospective memory which may better reflect the role of memory in daily life than conventional tests.


METHODS
Thirty-six subjects with type 1 diabetes participated, 20 with normal hypoglycaemia awareness (NHA) and 16 with impaired hypoglycaemia awareness (IHA). Each underwent a hypoglycaemic clamp with target blood glucose 2.5 mmol/l. Prior to hypoglycaemia, subjects attempted to memorise instructions for a prospective memory task, and recall was assessed during hypoglycaemia. Subjects then completed the learning and immediate recall stages of three conventional memory tasks (word recall, story recall, visual recall) during hypoglycaemia. Euglycaemia was restored and delayed memory for the conventional tasks was tested. The same procedures were completed in euglycaemic control studies (blood glucose 4.5 mmol/l).


RESULTS
Hypoglycaemia impaired performance significantly on the prospective memory task (p = 0.004). Hypoglycaemia also significantly impaired both immediate and delayed recall for the word and story recall tasks (p < 0.01 in each case). There was no significant deterioration of performance on the visual memory task. The effect of hypoglycaemia did not differ significantly between subjects with NHA and IHA.


CONCLUSIONS
Impaired performance on the prospective memory task during hypoglycaemia demonstrates that recall is disrupted by hypoglycaemia. Impaired performance on the conventional memory tasks demonstrates that learning is also disrupted by hypoglycaemia. Results of the prospective memory task support the relevance of these findings to the everyday lives of people with diabetes.
Warren
R E
RE
Department of Diabetes, Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh, EH16 4SA, UK.
Zammitt
N N
NN
Deary
I J
IJ
Frier
B M
BM
D000208:Acute Disease; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D016022:Case-Control Studies; D003071:Cognition / Q000502:physiology; D003922:Diabetes Mellitus, Type 1 / Q000150:complications / Q000503:physiopathology*; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007003:Hypoglycemia / Q000209:etiology / Q000503:physiopathology*; D007858:Learning / Q000502:physiology; D008297:Male; D008568:Memory / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology*; D011446:Prospective Studies; D015203:Reproducibility of Results
D001786:Blood Glucose