Self-monitoring of blood glucose changed non-insulin-treated Type 2 diabetes patients' beliefs about diabetes and self-monitoring in a randomized trial

Aims: To determine whether differences in beliefs about diabetes and its treatment resulted from different intensities of self-monitoring of blood glucose (SMBG) in non-insulin treated patients with Type 2 diabetes in the Diabetes Glycaemic Education and Monitoring (DiGEM) trial. Methods: Patients (n = 453) were randomized to usual care, less-intensive SMBG and more intensive SMBG. Beliefs about diabetes were measured with a standard questionnaire (the revised Illness Perceptions Questionnaire; IPQ-R). Changes in beliefs were analysed using analysis of covariance (ancova) with adjustment for baseline values. Mediation analyses assessed whether differences in behavioural outcomes between groups could be attributed to differences in beliefs. Results: Completed questionnaires were returned by 339 patients (74.8%). Respondents were mean (± sd) age 65.9 ± 10 years and with diabetes duration of 4.8 ± 4.7 years (median 36, range 1-384 months). Concerns about the consequences of diabetes increased in both self-monitoring groups, relative to control subjects [P = 0.004; Cohen's d standardized effect size = 0.19 less intensive and d = 0.36 more intensive monitoring]. No other beliefs about diabetes differed between groups. Beliefs about the importance of self-testing increased in both self-monitoring groups relative to the usual-care group (P < 0.001; d = 0.57 less intensive and d = 0.63 more intensive monitoring). Changes in psychological well-being did not differ between groups, but control patients reported greater increases in general (P = 0.014) and specific (P < 0.001) dietary adherence than did patients in the self-monitoring groups. These outcomes were not mediated by intervention-related changes in beliefs. Conclusions: Despite changes in some beliefs about diabetes differing between groups there were no corresponding changes in self-reported health behaviours. This suggests that changes in illness beliefs resulting from SMBG do not cause changes in diabetes-related health behaviours. © 2008 The Authors.