Methodological issues in a cluster-randomized trial to prevent dementia by intensive vascular care

J Nutr Health Aging. 2010 Apr;14(4):315-7. doi: 10.1007/s12603-010-0072-3.


Objectives: Description of methodological issues in a trial designed to evaluate if a multi-component intervention aimed at vascular risk factors can prevent dementia.

Design, setting and participants: Multi-center, open, cluster-randomized controlled clinical trial (preDIVA) including 3535 non-demented subjects aged 70-78, executed in primary practice and coordinated from one academic hospital. General practices are randomized to standard care or intensive vascular care.

Intervention: Vascular care consists of 4-monthly visits to a practice nurse who monitors all cardiovascular risk factors. Hypertension, hypercholesterolemia, overweight, lack of physical exercise and diabetes are strictly controlled according to a protocol and treated in a way, tailored to the characteristics of individual participants.

Measurements: Primary outcomes are incident dementia and disability; secondary outcomes are mortality, vascular events (stroke, myocardial infarction, peripheral vascular disease), cognitive decline and depression.

Results: Between May 2006 and February 2009, 3535 subjects from 115 general practices have been included. The clusters have an average size of 31 (SD 22, range 2-114). 1658 Patients from 52 practices were randomized to the standard care condition and 1877 patients in 63 practices to the vascular care condition.

Discussion: When designing a cluster-randomized trial, clustering of patient data within GP practices leads to a loss of power. This should be adjusted for in the power calculation. Since intensive vascular care will probably lead to a reduction in cardiovascular mortality, the competing risks of mortality and dementia should be taken into account.

Publication types

  • Multicenter Study
  • Randomized Controlled Trial

MeSH terms

  • Aged
  • Cardiovascular Diseases / mortality
  • Cardiovascular Diseases / prevention & control*
  • Cluster Analysis
  • Dementia / prevention & control*
  • Depression
  • Disease Progression
  • Humans
  • Randomized Controlled Trials as Topic / methods*
  • Reference Values
  • Risk Factors
  • Treatment Outcome