Determinants of Dropout and Nonadherence in a Dementia Prevention Randomized Controlled Trial: The Prevention of Dementia by Intensive Vascular Care Trial

OBJECTIVES: To explore and compare sociodemographic, clinical, and neuropsychiatric determinants of dropout and nonadherence in older people participating in an open-label cluster-randomized controlled trial-the Prevention of Dementia by Intensive Vascular care (preDIVA) trial-over 6 years. DESIGN: Secondary analysis. SETTING: One hundred sixteen general practices in the Netherlands. PARTICIPANTS: Community-dwelling individuals aged 70 to 78 (N = 2,994). INTERVENTION: Nurse-led multidomain intervention targeting cardiovascular risk factors to prevent dementia. MEASUREMENTS: The associations between participant baseline sociodemographic (age, sex, education), clinical (medical history, disability, cardiovascular risk), neuropsychiatric (depressive symptoms (Geriatric Depression Scale-15), and cognitive (Mini-Mental State Examination)) characteristics and dropout from the trial and nonadherence to the trial intervention were explored using multi-level logistic regression models. RESULTS: Older age, poorer cognitive function, more symptoms of depression, and greater disability were the most important determinants of dropout of older people. The presence of cardiovascular risk factors was not associated with dropout but was associated with nonadherence. Being overweight was a risk factor for nonadherence, whereas people with high blood pressure or a low level of physical exercise adhered better to the intervention. The association between poorer cognitive function and symptoms of depression and dropout was stronger in the control group than in the intervention group, and vice versa for increased disability. CONCLUSION: In a large dementia prevention trial with 6-year follow-up, dropout was associated with older age, poorer cognitive function, symptoms of depression, and disability at baseline. These findings can help to guide the design of future dementia prevention trials in older adults. The associations found between cardiovascular risk factors and nonadherence need to be confirmed in other older populations receiving cardiovascular prevention interventions.