Cognitive dysfunction in adults with Type 1 (insulin-dependent) diabetes mellitus of long duration: effects of recurrent hypoglycaemia and other chronic complications

Abstract

To examine the long-term effects of recurrent severe hypoglycaemia and other biomedical complications on mental efficiency, a battery of cognitive tests was administered to 142 Type 1 (insulin-dependent) diabetic adult patients (age 33.5 +/- 5.6 years; mean +/- SD) and 100 demographically similar non-diabetic control subjects. All diabetic subjects had been diagnosed before the age of 17 years. Diabetic subjects with one or more complications (distal symmetrical polyneuropathy; advanced background or proliferative retinopathy; overt nephropathy; one or more episodes of severe hypoglycaemia) performed significantly (p < 0.001) more poorly than non-diabetic control subjects on tests requiring sustained attention, rapid analysis of visuospatial detail, and hand eye co-ordination. Regression analyses indicated that the best biomedical predictor of cognitive test performance was a diagnosis of polyneuropathy. Although severe recurrent hypoglycaemia was not associated with performance on any test, the neuropathy x recurrent hypoglycaemia interaction term was significant. These results suggest that in adults with Type 1 diabetes of long duration, recurrent hypoglycaemia does not appear to influence cognitive performance directly, but may interact with neuropathy to exaggerate or otherwise magnify the extent of neurobehavioural dysfunction.

The effect of pain on cognitive function: A review of clinical and preclinical research

“…Chronic pain patients display slower reaction times than matched controls in a variety of standardised cognitive tests (Alanoglu et al, 2005;Antepohl et al, 2003;Biessels et al, 2007;Calandre et al, 2002;Harman and Ruyak, 2005;Sjogren et al, 2005), in particular on tests related to psychomotor ability (Harman and Ruyak, 2005;Lee et al, 2010;Ryan, 2005;Ryan et al, 1993;Ryan et al, 1992). Impaired perceptual learning ability has also been shown in chronic pain patients (Maihofner and DeCol, 2007).…”

“…Clinically, executive function is assessed using interference tasks such as the Wisconsin Card Sorting Test (Grant and Berg, 1948), the Process Dissociation Procedure (Jacoby, 1991), and flexibility tasks such as the Trail Making Test (Adjutant General's Office, 1944). Patient performances on these tests appear to show that controlled executive-type functions are affected by chronic pain (Karp et al, 2006;Ryan et al,1993;Verdejo-Garcia et al, 2009;Weiner et al, 2006), and may be more severely affected than less complex, automatic processes (for example fixed sequences of operations that do not require higher control) (Grisart and Van der Linden, 2001) (Table 1). Complex tests of attention, such as those that involve interference or attention switching, may require executive function and chronic pain patients perform poorly on such tests (Bosma and Kessels, 2002;Eccleston, 1994;Karp et al, 2006;Ryan et al, 1993).…”

“…Patient performances on these tests appear to show that controlled executive-type functions are affected by chronic pain (Karp et al, 2006;Ryan et al,1993;Verdejo-Garcia et al, 2009;Weiner et al, 2006), and may be more severely affected than less complex, automatic processes (for example fixed sequences of operations that do not require higher control) (Grisart and Van der Linden, 2001) (Table 1). Complex tests of attention, such as those that involve interference or attention switching, may require executive function and chronic pain patients perform poorly on such tests (Bosma and Kessels, 2002;Eccleston, 1994;Karp et al, 2006;Ryan et al, 1993). For example, Eccleston (1994) showed that pain affected performance on an attentional-interference task, but only when the task was at its most complex.…”

Cognitive efficiency declines over time in adults with Type 1 diabetes: effects of micro- and macrovascular complications

“…Not only were our diabetic subjects impaired on tasks requiring psychomotor speed or spatial information processing, but individuals with one or more biomedical complication showed more cognitive impairment than those without complications. Of the biomedical variables examined, clinically significant distal symmetrical polyneuropathy (DSP) and/or elevated glycosylated haemoglobin values were most strongly associated with psychomotor slowing [5,16].…”

Hypoglycaemia in diabetes mellitus - protecting the brain

“…In general, the loss of brain function due to hypoglycaemia presents in any degree from mild confusion or disinhibition to coma and full recovery apparently occurs within an hour of restoration of normoglycaemia [3]. There are concerns that recurrent episodes of hypoglycaemia-associated coma may result in permanent damage to cortical (intellectual) function although in adults the data are inconclusive, with some studies suggesting an acceleration of the age-related decline in performance on IQ testing [4], while others relate this to associated diabetic neuropathy [5]. Prospective studies of people who have been at particular risk for recurrent severe hypoglycaemia show no effect on long-term cognitive function [6,7].…”