The Effects of Type 1 Diabetes on Cognitive Performance

Abstract

OBJECTIVE -To investigate the exact nature and magnitude of cognitive impairments in patients with type 1 diabetes and the possible association with other disease variables, such as recurrent episodes of hypoglycemia and metabolic control.RESEARCH DESIGN AND METHODS -MedLine and PsycLit search engines were used to identify studies on cognitive performance in patients with type 1 diabetes. Effect sizes (Cohen's d), which are the standardized differences between the experimental and the control group, were calculated. In the meta-analysis, a combined d value was calculated, expressing the magnitude of associations across studies.RESULTS -A total of 33 studies were identified that met the inclusion criteria. Compared with nondiabetic control subjects, the type 1 diabetic group demonstrated a significantly lowered performance on the following cognitive domains: intelligence (d ϭ Ϫ0.7), speed of information processing (d ϭ Ϫ0.3), psychomotor efficiency (d ϭ Ϫ0.6), visual (d ϭ Ϫ0.4) and sustained attention (d ϭ Ϫ0.3), cognitive flexibility (d ϭ Ϫ0.5), and visual perception (d ϭ Ϫ0.4). Lowered cognitive performance in diabetic patients appeared to be associated with the presence of microvascular complications but not with the occurrence of severe hypoglycemic episodes or with poor metabolic control.CONCLUSIONS -In patients with type 1 diabetes, cognitive dysfunction is characterized by a slowing of mental speed and a diminished mental flexibility, whereas learning and memory are spared.The magnitude of the cognitive deficits is mild to moderate, but even mild forms of cognitive dysfunction might hamper everyday activities since they can be expected to present problems in more demanding situations. Diabetes Care 28:726 -735, 2005

Voxel-based morphometry demonstrates reduced grey matter density on brain MRI in patients with diabetic retinopathy

“…The relationship between the development of this encephalopathy and exposure to chronic hyperglycaemia, leading to microangiopathy, is not well established. A recent meta-analysis concluded that lowered cognitive performance of patients with type 1 diabetes appears not to be associated with recurrent episodes of severe hypoglycaemia, as often speculated, but rather with microvascular complications such as retinopathy [2]. A longitudinal study [3] showed that cognitive efficiency may decline over time in diabetic adults, and that this neurocognitive change may be linked, at least in part, to the occurrence of microvascular complications such as proliferative retinopathy and to elevated blood pressure.…”

Diabetic encephalopathy: a concept in need of a definition

“…The reported prevalence is about 40% in long-standing or poorly controlled diabetes [2]. Cognitive dysfunction in diabetes is characterised by lowered performance on several cognitive domains, most notably slowing of mental speed and diminished flexibility [3]. The magnitude of these cognitive deficits appears mild to moderate, but can significantly hamper daily functioning, adversely affecting quality of life [4].…”

“…As the relation between cognitive complaints and objective dysfunction is weak, we do not regard subjective complaints about cognitive functioning as a prerequisite for diagnosis of DACD. As cognitive dysfunction in type 1 diabetes is usually mild to moderate [3], we chose a performance >1.5 SD below that of controls as a criterion for DACD. Future research may refine the currently proposed criteria.…”

Ti: Cognitive Function in Diabetes Mellitus Patients

“…Overall, summarizing all studies and all cognitive domains (overall cognition), there is a modest but highly significant difference in cognitive performance between diabetic patients and non-diabetic control subjects. The pattern of cognitive findings does not suggest an overall impairment of cognitive function but is characterized by a slowing of mental speed and a diminished mental flexibility [17] . Although the magnitude of most of these cognitive problems is relatively modest moderate forms of cognitive dysfunction can potentially hamper everyday activities, and they can be expected to present problems in more demanding situations [17] .…”