Abstract
OBJECTIVE: To assess whether intensified insulin treatment, with an increased frequency of hypoglycaemic episodes, leads to cognitive deterioration. DESIGN: Prospective randomised trial of intensified conventional treatment and standard treatment. SETTING: Outpatient clinic for patients with insulin dependent diabetes. SUBJECTS: 96 patients with insulin dependent diabetes, high blood glucose concentrations, and non-proliferative retinopathy were randomised to intensified conventional treatment (n = 44) or standard treatment (n = 52). MAIN OUTCOME MEASURES: Glycated haemoglobin concentration (metabolic control); the number of hypoglycaemic episodes reported by patients at each visit; results of computerised neuropsychological tests performed at entry and after five years. RESULTS: Mean glycated haemoglobin concentration during the study was 7.2% (SE 0.1%) with intensified conventional treatment and 8.7 (0.1%) with standard treatment (p less than 0.001). During five years 34 (77%, 95% confidence interval 53% to 100%) of the patients given intensified treatment and 29 (56%, 36% to 75%) of the others had at least one episode of serious hypoglycaemia (p less than 0.05). The intensified conventional treatment group had a mean of 1.1 episodes of serious hypoglycaemia per patient per year compared with 0.4 episodes in the standard treatment group. Results of the neuropsychological tests were similar in the two groups after five years. CONCLUSIONS: Intensified conventional insulin treatment led to lower blood glucose concentrations and a higher frequency of hypoglycaemic episodes, but patients showed no signs of cognitive deterioration.