Absence of an association between insulin-dependent diabetes mellitus and developmental learning difficulties

Type 1 Diabetes Mellitus and Cognitive Impairments: A Systematic Review

Type 1 diabetes mellitus (T1DM) is a major subtype of diabetes and is usually diagnosed at a young age with insulin deficiency. The life expectancy of T1DM patients has increased substantially in comparison with that three decades ago due to the availability of exogenous insulin, though it is still shorter than that of healthy people. However, the relation remains unclear between T1DM and dementia as an aging-related disease. We conducted a systematic review of existing literature on T1DM and cognition impairments by carrying out searches in electronic databases Medline, EMBASE, and Google Scholar. We restricted our review to studies involving only human subjects and excluded studies on type 2 diabetes mellitus or non-classified diabetes. A meta-analysis was first performed on the relationship between T1DM and cognitive changes in youths and adults respectively. Then the review focused on the cognitive complications of T1DM and their relation with the characteristics of T1DM, glycemic control, diabetic complications, comorbidities, and others. First, age at onset, disease duration, and glycemic dysregulation were delineated for their association with cognitive changes. Then diabetic ketoacidosis, angiopathy, and neuropathy were examined as diabetic complications for their involvement in cognitive impairments. Lastly, body mass index and blood pressure were discussed for their relations with the cognitive changes. Future studies are needed to elucidate the pathogenesis of T1DM-related cognitive impairments or dementia.

Type 1 diabetes-associated cognitive decline: a meta-analysis and update of the current literature

BACKGROUND

Type 1 diabetes (T1D) can have a significant impact on brain structure and function, which is referred to as T1D-associated cognitive decline (T1DACD). Diabetes duration, early onset disease, and diabetes-associated complications are all proposed as factors contributing to T1DACD. However, there have been no comparisons in T1DACD between children and adults with T1D. To obtain a better insight into the occurrence and effects of T1DACD in T1D, the aim of the present meta-analysis was to investigate differences between children and adults and to analyse factors contributing T1DACD.

METHODS

Two electronic databases were consulted: PubMed and ISI Web of Knowledge. Literature published up until the end of 2013 was included in the analysis. Effect sizes (Cohen's d), which are standardized differences between experimental and control groups, were calculated.

RESULTS

There was a small to modest decrease in cognitive performance in T1D patients compared with non-diabetic controls. Children with T1D performed worse while testing for executive function, full intelligence quotient (IQ), and motor speed, whereas adults with T1D performed worse while testing the full, verbal and performance IQ, part of the executive function, memory, spatial memory, and motor speed. Episodes of severe hypoglycemia, chronic hyperglycemia, and age of onset can be significant factors influencing cognitive function in T1D.

CONCLUSIONS

The findings in the literature suggest that T1DACD is more severe in adults than children, indicating that age and diabetes duration contribute to this T1DACD.

Dietary ω-3 polyunsaturated fatty acids improves learning performance of diabetic rats by regulating the neuron excitability

Previous research has demonstrated that diabetes induced learning and memory deficits. However, the mechanism of memory impairment induced by diabetes is poorly understood. Dietary fatty acids, especially polyunsaturated fatty acids (PUFA), have been shown to enhance learning and memory and prevent memory deficits in various experimental conditions. Sprague-Dawley rats were used in the present study to investigate the effect of fish oil supplementation on spatial learning and memory of streptozotocin (STZ)-induced diabetic rats with the Morris Water Maze. The excitability of CA1 pyramidal neurons and the related ionic currents was also examined. Diabetes impaired spatial learning and memory of rats. Diabetes decreased the sodium currents and increased the potassium currents, and further led to the reduction of excitability of CA1 pyramidal neurons, effects which may contribute to the behavioral deficits. Fish oil dietary supplementation decreased the transient currents and Kv4.2 expression in the hippocampus and partially improved learning performance of diabetic rats. The results of the present study suggested that sodium and potassium currents contributed to the inhibitory effect of diabetes on neuron excitability, further influencing learning and memory processing. Dietary fish oil may modulate the membrane excitability and is a possible strategy for preventing the impairments of diabetes on hippocampal function.

Cognitive function in children with type 1 diabetes: a meta-analysis

OBJECTIVE

To quantify the magnitude and pattern of cognitive difficulties in pediatric type 1 diabetes as well as the effects associated with earlier disease onset and severe hypoglycemia.

RESEARCH DESIGN AND METHODS

Pediatric studies of cognitive function since 1985 were identified for study inclusion using MEDLINE and PsycInfo. Effect size (ES, Cohen's d) between the diabetic and control groups, expressed in SD units, were calculated within cognitive domains to standardize meta-analysis test performance.

RESULTS

The meta-analysis sample of 2,144 children consisted of 1,393 study subjects with type 1 diabetes and 751 control subjects from 19 studies. Overall, type 1 diabetes was associated with slightly lower overall cognition (ES -0.13), with small differences compared with control subjects across a broad range of domains, excluding learning and memory, which were similar for both groups. Learning and memory skills, both verbal and visual (-0.28 and -0.25), were more affected for children with early-onset diabetes (EOD) than late-onset diabetes (LOD), along with attention/executive function skills (-0.27). Compared with nondiabetic control subjects, EOD effects were larger, up to one-half SD lower, particularly for learning and memory (-0.49). Generally, seizures were associated with a negligible overall cognition ES of -0.06, with slight and inconsistent cognitive effects found on some measures, possibly reflecting the opposing effects of poorer versus better metabolic control.

CONCLUSIONS

Pediatric diabetes generally relates to mildly lower cognitive scores across most cognitive domains. Cognitive effects are most pronounced and pervasive for EOD, with moderately lower performance compared with control subjects. Seizures are generally related to nominal, inconsistent performance differences.

Learning disorders in epilepsy

Learning disorders (LD) are disorders interfering with academic performance or with daily living activities requiring reading, writing, or mathematical abilities in subjects with a normal intelligence quotient. The prevalence of LD in the general population has been found to be 2-10% and reading disorders are the most frequent subtype. Epilepsy is one of the commonest neurological disorders in childhood with an estimated prevalence in 4-5/1,000. Epilepsy is considered to be idiopathic or cryptogenic in approximately two-thirds of cases. LD are more common in people with epilepsy than in the general population: about 25% of patients with epilepsy are said to have LD. Various psychosocial, medication-related, and epilepsy-related factors may be associated with LD in epilepsy. LD can be either permanent or state-dependent. Permanent LD are caused by a brain lesion and/or a stable brain dysfunction. In contrast, state-dependent LD are potentially reversible and treatable; they are caused by epilepsy-related factors. If allowed to persist for a long period, a state-dependent LD may become permanent.

The social and economic consequences of childhood-onset Type 1 diabetes mellitus across the lifecourse: a systematic review

BACKGROUND

The incidence of childhood-onset (Type 1) diabetes is high, and increasing, particularly among the very young. The aim of this review was to determine the longer-term social consequences of having diabetes as a child and to determine whether adverse consequences are more severe for disadvantaged children.

METHODS

Results from published and unpublished studies were synthesized narratively to examine the impact of diabetes on education, employment and income in adulthood. The question of whether the impact differed for different social groups was also examined.

RESULTS

Case-control studies found that children with diabetes missed more school than healthy children. Most studies of attainment found no differences between children with diabetes and non-diabetic control subjects or the local population, although poor metabolic control, early-onset, longer illness duration and serious hypoglycaemic events were associated with underachievement. People with childhood-onset diabetes may experience disadvantage in employment, and have a lower income in adulthood, although diabetic complications appear to be the most important determinant of social consequences in later life.

CONCLUSIONS

Many children with diabetes--especially late-onset--perform equally well at school despite increased rates of absence, but it is not yet clear whether specific subgroups are at greater risk of educational underperformance. People with childhood-onset diabetes, however, do appear to experience some disadvantage in adult employment. Qualitative research and cohort studies are needed to fill key gaps in the existing evidence base. Future research must also examine the impact of diabetes-related risk factors on socio-economic consequences.

Effects of insulin on long-term potentiation in hippocampal slices from diabetic rats

AIMS/HYPOTHESIS

Cognitive deficits occur commonly in diabetic patients. It is unclear whether these impairments result from hypoglycaemia during intensive insulin therapy, or from the diabetes itself. The aim of this study was to examine if impaired energy utilization resulting from insulin deficiency contributes to impaired long-term potentiation (reflecting impaired synaptic plasticity). As long-term potentiation is considered a candidate cellular mechanism underlying learning and memory, understanding how diabetes alters long-term potentiation may provide insight into mechanisms producing cognitive deficits in diabetes.

METHODS

Electrophysiologic recordings were used to study long-term potentiation in the CA1 region of hippocampal slices from healthy rats and rats with streptozotocin-induced diabetes.

RESULTS

Long-term potentiation was difficult to induce in slices from diabetic rats in standard recording buffer (contains 10 mmol/l glucose). In slices from diabetic rats, increasing extracellular glucose failed to recover long-term potentiation induction, but 10 mmol/l pyruvate added to standard buffer enabled long-term potentiation induction. Moreover, incubation of slices from diabetic rats with insulin enabled long-term potentiation induction in standard buffer. Acute administration of streptozotocin alone did not impair long-term potentiation in slices from healthy animals, and changing extracellular glucose concentrations over the range of 5 mmol/l to 30 mmol/l did not alter long-term potentiation in slices from control rats.

CONCLUSIONS/INTERPRETATION

These observations suggest that impaired energy utilization from insulin deficiency, rather than the accompanying hyperglycaemia, impair long-term potentiation in diabetes. Impaired hippocampal synaptic plasticity could contribute to learning and cognitive impairment in diabetic patients.

Child and parental mental ability and glycaemic control in children with Type 1 diabetes

AIMS

Many psycho-social factors can affect the glycaemic control of children with Type 1 diabetes, but the influence of the intelligence of the child and their parents has not been reported.

METHODS

Seventy-eight children and adolescents with Type 1 diabetes and their mothers performed standardized tests to assess psychometric intelligence. The children were aged (median (range)) 12.0 (5-17) years with duration of diabetes 5.0 (1.0-13.0) years and required an insulin dose of (mean +/- SD) 1.0 +/- 0.3 U/kg per day. The children completed the Wide Range Achievement Test 3 reading test (WRAT3) and Raven's Standard Progressive Matrices (RSPM). A mean annual HbA1c was calculated for each subject (8.6 +/- 1.4%). The mothers performed the National Adult Reading Test (NART) and provided details of the occupation of the main wage-earner in the family from which social class (SC) was derived.

RESULTS

The HbA1c of the child correlated with their age (r = 0.26, P = 0.02), SC (Kendall's rank correlation, tau = 0.17, P = 0.03) and with the NART error score of their mother (r = 0.28, P = 0.01), but no correlation was observed with the child's WRAT3 or RSPM score. Stepwise regression revealed that age and NART error score were the strongest independent determinants of glycaemic control (total adjusted r2 = 0.117).

CONCLUSIONS

Parental intelligence appears to have a significant influence on the glycaemic control of a child with Type 1 diabetes, accounting for 7.6% of the reliable variance in HbA1c.