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 
multilevel 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.