1 Medical Psychological Center, The Second Xiangya Hospital, Central South University, Changsha, China.
2 Medical Psychological Institute of Central South University, Changsha, China.
3 Center for Clinical Research in Health & Department of Psychology, Concordia University, Montreal, Quebec, Canada.
4 Culture and Mental Health Research Unit & Lady Davis Institute, Jewish General Hospital, Montreal, Quebec, Canada.

Aims/introduction: To examine the magnitude and pattern of cognitive dysfunction in children with type 1 diabetes, and the possible effects associated with other disease variables, such as early onset diabetes, severe hypoglycemia and hyperglycemia.

Materials and methods: We carried out a meta-analysis using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. We searched MedLine, Embase and PsycINFO to identify studies on cognitive function in children with type 1 diabetes that were published up until 30 September 2016. Effect sizes understood as the standardized mean differences between groups with diabetes and control groups (i.e., Hedges' g) were calculated to quantify the extent of cognitive dysfunction in those groups consisting of children with diabetes.

Results: A total of 19 studies met our inclusion criteria, comprising 1,355 participants with type 1 diabetes and 696 controls. Compared with non-diabetic controls, children with type 1 diabetes showed a significantly poorer cognitive performance overall (g = -0.46), as well as specific deficits in full-scale intelligence (g = -1.06), attention (g = -0.60) and psychomotor speed (g = -0.46). Glycemic extremes were associated with poorer overall cognition (g = -0.18), as well as slightly lower performance in memory (g = -0.27).

Conclusions: We found that type 1 diabetes was associated with cognitive dysfunction characterized by a lowered intelligence, diminished attention and a slowing of psychomotor speed. Glycemic extremes, which are described as a period of high glucose levels and severe hypoglycemia, were related to cognitive dysfunction in children with type 1 diabetes.