Introduction and objectives Cognitive impairments have been observed in people with type 1 and 2 diabetes. People with cystic fibrosis (CF) who have developed CF related diabetes (CFRD) also show some degree of impairment relative to healthy controls. The aim of this study was to examine cognitive function in people with CFRD after an 18 (± 6) month period to assess any change in performance.

Method Adult (>16 years old), pancreatic insufficient patients with insulin treated CFRD registered to a large UK CF unit who had adequate verbal and written English were eligible. Cognitive performance was assessed using parallel versions of tests from the Cambridge Neuropsychological Test Automated Battery (CANTAB). Subjective ratings of sleep, stress, mood, cognitive performance and minor daily cognitive errors were also collected. At baseline, 67 people were tested; 49 non transplanted and 18 post transplantation patients. Twelve patients were lost to follow-up. To date, 43 people have been retested after an 18 (± 6) month period; 35 non transplanted and 8 post transplantation patients.

Results At follow up, blood glucose levels were significantly lower during testing (reflecting better glycaemic control in some patients) and people reported significantly fewer occurrences of minor daily cognitive errors within the past 6 months. There was no change in performance between baseline and follow up on tests of motor function, visual memory and new learning, immediate pattern recognition, working memory and mental flexibility. On tests of immediate and delayed verbal memory, delayed pattern recognition and processing speed, performance had significantly improved at follow up.

Conclusion Cognitive function is impaired in people with CFRD but remains stable over an 18 (±6) month period. Deficits in cognitive performance may impact upon quality of life and ability to adhere to treatment.