Acute Hypoglycemia Impairs Nonverbal Intelligence
Importance of avoiding ceiling effects in cognitive function testing
- Roderick E. Warren, MRCP1,
- Kate V. Allen, MRCP1,
- Andrew J. Sommerfield, MRCP1,
- Ian J. Deary, PHD2 and
- Brian M. Frier, MD1
- 1Department of Diabetes, Royal Infirmary of Edinburgh, Edinburgh, U.K.
- 2Department of Psychology, University of Edinburgh, Edinburgh, U.K.
- Address correspondence and reprint requests to Professor Brian M. Frier, Department of Diabetes, Royal Infirmary of Edinburgh, 51 Little France Crescent, Edinburgh EH16 4SA, U.K. E-mail: brian.frier{at}luht.scot.nhs.uk
- AH5, Alice Heim 5 test
- DSST, Digit Symbol Substitution
- RAPM, Raven’s Advanced Progressive Matrices
- RPM, Raven’s Progressive Matrices
- TMB, Trail Making B
Acute hypoglycemia causes a progressive, reversible deterioration in cognitive function that becomes detectable at blood glucose concentrations below ∼3.0–3.4 mmol/l (1). In an earlier study in nondiabetic subjects, we reported that several facets of attention deteriorated significantly at an arterialized blood glucose level of 2.6 mmol/l (2). However, performance on Raven’s Progressive Matrices (RPM) was not significantly impaired at either 20 min or completion of the test (with no time limit). This was unexpected, because, previously, various domains of cognitive function had consistently been impaired at this level of hypoglycemia (1). Additionally, the RPM is acknowledged as being among the best indicators of general fluid intelligence (3) and has a substantial correlation with working memory (4), which is exquisitely sensitive to hypoglycemia (5).
Hypoglycemia disrupts performance on different cognitive function tests to a variable degree, leading to speculation that different mental functions vary …
