Original articles
Neurocognitive Functioning in Children Diagnosed with Diabetes Before Age 10 Years

https://doi.org/10.1016/S1056-8727(98)00029-4Get rights and content

Abstract

Our objective was to determine scores on tests of neurocognitive functioning in children diagnosed with diabetes before age 10 years and to determine the association of age of diagnosis, duration of diabetes, subtle hypoglycemia, severe hypoglycemia, and history of hypoglycemic seizures with these neurocognitive test scores. Fifty-five of 62 eligible patients with a mean age of 7.9 ± 1.6 years followed in our center were given the Woodcock-Johnson Psychoeducational Battery, Beery Developmental Test of Visual-Motor Integration, Finger Tapping, Grooved Pegboard, and Verbal Selective Reminding tests to evaluate the following domains: memory/attention, visual–perceptual, broad cognitive function, academic achievement, and fine motor speed/coordination. Fifteen age-matched siblings served as controls. Twenty-seven subjects were less than 5 years of age when diagnosed with diabetes, the mean age at diagnosis was 4.5 ± 2.1 years of age, and mean diabetes duration was 2.6 ± 2.0 years. Eighteen patients had a history of severe hypoglycemia, eight of whom had hypoglycemic seizures. The mean HbA1c was 7.8 ± 1.1% for the year prior to testing. Our results showed that the overall mean scores for the extensive neurocognitive battery were within the normal range and were comparable to the scores of the age-matched sibling controls. Age of diagnosis and duration of diabetes did not relate to neurocognitive test results. Mean HbA1c had a negative association with some tests of memory/attention (p < 0.03–0.04) and academic achievement (p < 0.005–0.03), while number of blood glucose levels less than mg/dL had a positive association with memory/attention (p < 0.004–0.04), verbal comprehension (p < 0.03) and academic achievement (p < 0.018–0.05). There was no association of neurocognitive test scores with severe hypoglycemia, but subjects with history of hypoglycemic seizures had a decrease in scores on tests assessing memory skills (p < 0.03) including short term memory and memory for words. These data suggest that overall neurocognitive test scores were within the normal range and comparable to controls. However, specific aspects of neurocognitive functioning may be adversely affected by having had a hypoglycemic seizure, but not by episodes of severe hypoglycemia without seizure. Lower HbA1c and an increase in the number of blood glucose levels less than 70 mg/dL (subtle hypoglycemia) which were associated with higher scores in some domains of academic achievement and memory suggests that stable glycemia may influence cognitive abilities and/or that successful diabetes management requires cognitive skills. Strategies to diminish the risk of seizures with hypoglycemia should be investigated.

Introduction

Despite the findings of the Diabetes Control and Complications Trial (DCCT),1 it remains controversial whether intensive diabetes management should be advocated in young children with type I diabetes.2, 3 One reason controversy exists is that the DCCT cohort included only adults and youth greater than 13 years of age. Therefore, it can only be hypothesized that younger children would appreciate the same reduction in long-term micro and macrocirculatory and neuropathic complications as their older counterparts as a result of improving glycemia. Similarly, it is controversial whether younger children might be more susceptible to the adverse effects from severe hypoglycemia that appears to be increased with present-day intensive management.

Previous studies in children have shown that both subtle and severe hypoglycemia, with and without seizures, may be associated with a decrease in neurocognitive outcome,4, 5 and that children who have diabetes diagnosed before age 5–6 years may be particularly susceptible.6, 7, 8, 9, 10 It was unclear from these studies, however, whether the adverse effects on neurocognitive outcome were due only to prior hypoglycemia or whether there was an influence from other diabetes-related management issues. In addition, the neurocognitive deficits previously described were not in the broad cognition domain but rather they represented deficits in tests that specifically measured visual–spatial skills, motor speed and coordination, and memory abilities.

The purpose of the present longitudinal study was to determine the association between diabetes control, age at diagnosis, duration of diabetes, preceding glycemia and history of severe hypoglycemia or seizures and scores on tests of neurocognitive functioning in children 5–10 years of age with type I diabetes followed at Childrens Hospital Los Angeles. Test scores for children with diabetes were compared to age-matched sibling controls without diabetes. Overall cognitive functioning, academic achievement, memory/attention skills, visual/perceptual performance, motor speed and coordination, auditory processing, and verbal comprehension were the specific domains analyzed. The study was designed to examine the following hypotheses; that scores on tests of neurocognitive functioning will be higher in children with good diabetes control compared to children with poor control as assessed by HbA1c values, lower in children diagnosed with diabetes at an earlier age compared to children diagnosed later, lower in subjects with diabetes for a longer duration of time than in children more recently diagnosed, lower in children with more frequent episodes of subtle hypoglycemia (blood glucose levels < 70 mg/dL/month) compared to children with fewer episodes, lower in subjects with a history of severe hypoglycemia, particularly with a history of hypoglycemic seizure, compared to those without such a history, and lower in children with diabetes compared to their age-matched siblings.

Section snippets

Study Subjects

Fifty-five of 62 eligible children with type 1 diabetes, between the ages of 5 to 10 years, followed at Childrens Hospital Los Angeles who were primarily English-speaking, underwent testing with an extensive neurocognitive battery as part of a prospective outcome evaluation after parental informed consent was obtained. The mean age at diagnosis of diabetes for the study cohort was 4.5 ± 2.1 years; the mean duration of diabetes at the time of initial testing was 2.6 ± 2.0 years. The mean age of

Results

Table 1, Table 2 show the mean test scores on the extensive neurocognitive battery listed by domain tested, for the 55 subjects and for the sibling controls. Table 3 shows the association between individual test scores on the neurocognitive battery with the mean HbA1c, the age at diagnosis, and the number of blood glucose levels less than 70 mg/dL/month for the domains tested.

HbA1c: At entry, the mean HbA1c for the 55 study subjects was 7.8 ± 1.1% (range of 5.4–11.9%). Mean HbA1c had a negative

Discussion

Our data suggest that overall scores on tests of neurocognitive functioning in children diagnosed with diabetes before age 10 years were within the normal range for the domains tested. While scores were statistically comparable to the scores found in age-matched sibling controls, there was a trend of higher scores in siblings on 56% of the measures of academic achievement and on 22% of the measures of memory. Although this may be an artifact due to the small sample size of the sibling pairs, it

Acknowledgements

Supported in part by the NIH NCRR GCRC MO1 RR-43 and was performed at the GCRC at Childrens Hospital Los Angeles.

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    Presented at the American Diabetes Association Meeting, Boston, Massachusetts; June, 1997.

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