Abstract
BACKGROUND: Effective recruitment and retention strategies are essential in clinical trials. METHODS: The MemAID trial consisted of 12 visits during 24 weeks of intranasal insulin or placebo treatment and 24 weeks of post-treatment follow-up in older people with and without diabetes. Enhanced retention strategies were implemented mid study to address high drop-out rate. Baseline variables used in Cox regression models to identify dropout risk factors were: demographics and social characteristics, functional measures, metabolic and cardiovascular parameters, and medications. RESULTS: 244 participants were randomized; 13 (5.3%) were discontinued due to adverse events. From the remaining 231 randomized participants, 65 (28.1%) dropped out, and 166 (71.9%) did not. The Non-retention group included 95 participants not exposed to retention strategies, of which 43 (45.2%) dropped out. The Retention group included 136 participants exposed to enhanced retention strategies, of which 22 (16.2%) dropped out. Dropout risk factors included being unmarried, a longer diabetes duration, using oral antidiabetics as compared to not using, worse executive function and chronic pain. After adjusting for exposure to retention strategies, worse baseline executive function composite score (p = 0.001) and chronic pain diagnosis (p = 0.032) were independently associated with a greater risk of dropping out. The probability of dropping out decreased with longer exposure to retention strategies and the dropout rate per month decreased from 4.1% to 1.8% (p = 0.04) on retention strategies. CONCLUSIONS: Baseline characteristics allow prediction of dropping out from a clinical trial in older participants. Retention strategies has been effective at minimizing the impact of dropout-related risk factors. TRIAL REGISTRATION: Clinical trials.gov NCT2415556 3/23/2015 (www. CLINICALTRIALS: gov).