Is the success of the SLIMMER diabetes prevention intervention modified by socioeconomic status?  A randomised controlled trial. 
To explore the role of socioeconomic status (SES) in participation, programme attendance, programme acceptability, adherence to lifestyle guidelines, drop-out, and effectiveness in the SLIMMER diabetes prevention intervention.  SLIMMER was a randomised controlled intervention, carried out in a real-world setting, targeting 40- to 70-year-old adults at increased risk of developing type 2 diabetes (n=316).  The intervention group participated in a 10-month combined dietary and physical activity programme.  Measurements were carried out at baseline, 12months, and 18months.  Effectiveness was determined for fasting insulin, HbA1c, weight, BMI, waist circumference, and waist-to-height-ratio.  Differences between the low SES (no, primary, or lower secondary school) and higher SES group were tested using logistic regression and ANCOVA.  Fifty-two percent of the SLIMMER participants had a low SES.  No differences in participation were observed between the low and higher SES group.  The most important reason for non-participation in the low SES group was 'lack of interest' (32%), whereas in the higher SES group this was 'I already exercise enough' (31%).  Attendance, acceptability, adherence, drop-out, and effectiveness after 12months were similar in the low and higher SES group.  After 18months, the low SES group seemed to maintain slightly better effects for fasting insulin, HbA1c, and waist circumference.  The current study showed that participation, attendance, acceptability, adherence, drop-out, and effectiveness of the SLIMMER intervention were in general not modified by socioeconomic status.  The SLIMMER intervention can contribute to health promotion for individuals in both low and higher socioeconomic groups.