Severe Hypoglycemia and Intelligence in Adult Patients With Insulin-Treated Diabetes

Abstract

The IQ scores (WAIS-R) of 100 patients with insulin-treated diabetes (aged 25-52 yr) were compared with those of 100 healthy control subjects who were matched to the diabetic patients for sex, age, education, and social class. The diabetic group had lower WAIS-R performance and verbal IQ scores than the control group (P = 0.017 and P = 0.033, respectively) after controlling for premorbid IQ. The extent of the difference was modest, representing approximately 33% of an SD in IQ. When frequency of severe hypoglycemia was controlled for the difference in performance IQ between the diabetic patient group and the control group was abolished, whereas the difference between the groups in verbal IQ persisted. It is hypothesised that cumulative severe hypoglycemia might be the major factor in the slight performance IQ differences between diabetic patients and control subjects. The origin of the verbal IQ differences, although obscure, might be related to the social impact of the disorder.

Basal ganglia calcification in BB/E rats with diabetes

“…Factors such as exposure to severe hypoglycaemia, depression, macrovascular disease, hypertension, poor metabolic control and microvascular disease may all be implicated. 1,3,8 A few neuropathological studies in humans with diabetes of long duration have reported the presence of structural abnormalities, including microvascular and other changes such as 'pseudocalcinosis'. [9][10][11] However, many of these post-mortem studies were performed on adults who had concurrent renal failure and severe hypertension, which may themselves have been responsible for the neuropathological changes.…”

Intensive diabetes treatment and cognition: No long-lasting effects of recurrent hypoglycemia

“…Several earlier studies have suggested that severe hypoglycemia, over time, is associated with cognitive decline in people with type 1 diabetes [3,4]. When the DCCT reported that recurrent severe hypoglycemia did not permanently impact cognitive function over time [5] (data consistent with those of a smaller study previously published [6]), the report was met with some skepticism [7].…”

The Long-Term Sequelae of Severe Hypoglycemia on the Brain in Insulin-Dependent Diabetes Mellitus

“…(16), a positive correlation between the frequency of severe hypoglycemia and the degree of intellectual deficit was demonstrated. In an extension of the original study, impaired performance IQ was shown to be associated specifically with hypoglycemia, whereas a lower verbal lQwas a feature of diabetes per se and may be related to the social impact of the disease (15). Further characterization of the performance deficit associated with hypoglycemia demonstrated that decision and response initiation processes were affected in preference to the encoding and storage of information (17).…”

“…However, some evidence now suggests that recurrent exposure to severe hypoglycemia may have a deleterious effect on cognitive function which is cumulative and causes a gradual decline in intellectual ability over a period of years (12). Retrospective studies of adult patients with IDDM have demonstrated an association between a history of recurrent severe hypoglycemia (13)(14)(15)(16) and a modest degree of cognitive impairment with a mean lQ deficit of about 6 lQ points (14, 15, 17) (Fig.1). The cognitive deficits included motor skills, problem solving, visuospatial skills and tasks involving frontal lobe function.…”