Does the behavioural type-specific approach for type 2 diabetes promote changes in lifestyle? Protocol of a cluster randomised trial in Japan.

INTRODUCTION: Type 2 diabetes (T2D) is a significant problem, and lifestyle modifications including self-management are important. We have developed a structured individual-based lifestyle education (SILE) programme for T2D. With attention now being paid to techniques to change behaviour, we recently developed a behavioural type-specific SILE (BETSILE) programme. We aimed to evaluate the effectiveness of the BETSILE programme compared with the SILE programme for reducing glycated haemoglobin (HbA1c) in patients with T2D and special behavioural types by a cluster randomised controlled trial.

METHODS AND ANALYSIS: This is a 6-month cluster randomised controlled trial with two intervention arms (BETSILE vs SILE) provided in a medical care setting by randomising registered dietitians for patients with T2D aged 20-79 years. Patients' behavioural types were classified into four types (BT1 to BT4) using an assessment sheet. We will perform independent trials for BT1 and BT2. The primary endpoint is a change from the baseline HbA1c value at 6 months. Differences between the SILE and BETSILE groups will be primarily analysed following the intention-to-treat principle. Crude and multivariate adjusted effects will be examined after adjusting for covariates, using a general linear mixed-effects model for continuous variables and a logistic regression mixed-effects model for dichotomous variables. Sample sizes needed were calculated assuming effect sizes of 0.42 and 0.33 for BT1 and BT2, respectively, an intraclass correlation of 0.02, a significance level of 5% (two-sided), a power of 80%, and equal allocation of clusters to the two arms, with each cluster having three BT1 patients for the SILE and BETSILE arms and six BT2 patients for the SILE and BETSILE arms. We will need 16 dietitians for each arm, and a total 288 patients will be required.

ETHICS AND DISSEMINATION: This study has been approved by the Medical Ethical Committee of Teikyo University (No.15-222). Findings will be disseminated widely through peer-reviewed publications, etc.

TRIAL REGISTRATION NUMBER: UMIN 000023087; Pre-results.