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Impact of Diabetes and Its Treatment on Cognitive Function Among Adolescents Who Participated in the Diabetes Control and Complications Trial Gail Musen , PHD 1 , Alan M. Jacobson , MD 1 , Christopher M. Ryan , PHD 2 , Patricia A. Cleary , MS 3 , Barbara H. Waberski , MS 3 , Katie Weinger , EDD 1 , William Dahms , MD 4 † , Meg Bayless , RN 5 , Nancy Silvers , RN 6 , Judith Harth , RN 7 , Neil White , MD, CDE 8 and the Diabetes Control and Complications Trial/Epidemiology of Diabetes Interventions and Complications (DCCT/EDIC) Research Group * 1 Joslin Diabetes Center/Harvard Medical School, Boston, Massachusetts 2 Department of Psychiatry, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 3 Biostatistics Center, George Washington University, Rockville, Maryland 4 Case Western Reserve University, Cleveland, Ohio 5 University of Iowa College of Medicine, Iowa City, Iowa 6 Department of Epidemiology, University of Pittsburgh, Pittsburgh, Pennsylvania 7 University of Western Ontario Schulich School of Medicine, London, Ontario, Canada 8 Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri Corresponding author: Gail Musen, gail.musen{at}joslin.harvard.edu Abstract OBJECTIVE —The purpose of this study was to evaluate whether severe hypoglycemia or intensive therapy affects cognitive performance over time in a subgroup of patients who were aged 13–19 years at entry in the Diabetes Control and Complications Trial (DCCT). RESEARCH DESIGN AND METHODS —This was a longitudinal study involving 249 patients with type 1 diabetes who were between 13 and 19 years old when they were randomly assigned in the DCCT. Scores on a comprehensive battery of cognitive tests obtained during the Epidemiology of Diabetes Interventions and Complications follow-up study, ∼18 years later, were compared with baseline performance. We assessed the effects of the original DCCT treatment group assignment, mean A1C values, and frequency of severe hypoglycemic events on eight domains of cognition. RESULTS —There were a total of 294 reported episodes of coma or seizure. Neither frequency of hypoglycemia nor previous treatment group was associated with decline on any cognitive domain. As in a previous analysis of the entire study cohort, higher A1C values were associated with declines in the psychomotor and mental efficiency domain ( P < 0.01); however, the previous finding of improved motor speed with lower A1C values was not replicated in this subgroup analysis. CONCLUSIONS —Despite relatively high rates of severe hypoglycemia, cognitive function did not decline over an extended period of time in the youngest cohort of patients with type 1 diabetes. Footnotes Published ahead of print at http://care.diabetesjournals.org on 7 July 2008. Clinical trial reg. no. NCT00360893, clinicaltrials.gov. ↵ * A complete list of the individuals and institutions participating in the DCCT/EDIC Research Group appears in the following article: Jacobson AM, Ryan CM, Cleary P, Waberski B, Burwood A, Weinger K, Bayless M, Dahms W, Harth J: Long-term effects of diabetes and its treatment on cognitive function. N Engl J Med 356:1842-1852, 2007. ↵ † Deceased. Readers may use this article as long as the work is properly cited, the use is educational and not for profit, and the work is not altered. See http://creativecommons.org/licenses/by-nc-nd/3.0/ for details. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C Section 1734 solely to indicate this fact. See accompanying editorial, p. 2072 . Accepted June 25, 2008. Received March 25, 2008. DIABETES CARE