Adult Changes in Thought Study


  • Dr. Eric B. Larson

    Group Health Research Institute

  • MD. Paul Crane

    University of Washington

  • Erin Bowles

    Group Health Research Institute

  • Darlene White

    Group Health Research Institute

  • KatieRose Richmire

    Group Health Research Institute

General Design

Study design
Start Year
General Information on Follow Up (profile, frequency)

The participants are followed up with interviews every two years until diagnosis of dementia and/or Alzheimer's disease.

Recruitment Target
  • Individuals
Number of Participants
4,960 (No Limit)
Number of Participants with Biological Samples
4,960 (No Limit)
Supplementary information about number of participants

The ACT study is made up of three cohorts:

From 1994-1996 we enrolled a cohort of 2,581 people aged 65 years and older without dementia.

From 2000-2002, we enrolled an expansion cohort of 811 people using the same inclusion criteria.

From 2004-present, we began continuous enrollment using the same inclusion criteria to replace attrition from dementia, dropout, and death. We have a consistent cohort of ~2000 at risk for dementia. The total current enrollment of all three groups is 4,960.


Availability of data and biosamples

Possible Access to Data
Possible Access to Biosamples

Marker Paper

Kukull WA, Higdon R, Bowen JD, et al. Dementia and Alzheimer Disease Incidence: A Prospective Cohort Study. Arch Neurol. 2002;59(11):1737-1746. doi:10.1001/archneur.59.11.1737.

PUBMED 12433261



ACT population

Selection Criteria

Minimum age
  • United States of America

Seattle area.

Other Criteria

Participants with an existing diagnosis of dementia or those who were in a skilled nursing community were excluded.

Sources of Recruitment

Specific Population
  • Members of an association
Supplementary Information

Random sample of members of the Group Health Cooperative of Puget Sound

Sample Size

Number of Participants
Number of Participants with Biological Samples
Supplementary Information about Population

Recruitment 1: 2581 participants

Recruitment 2: 811 participants

Recruitment 3: Seeks to maintain population of approximately 2000 participants (ongoing)

Data Collection Events

# Name Description Start End
0 ACT - Recruitment 1 1994 1996
1 ACT - Follow-up 1996 2014
2 ACT - Recruitment 2 2000 2002
3 ACT - Recruitment 3 2004 2014

Individual Studies Included

Acronym Name Study design Participants Countries

Harmonization Projects Included

Acronym Name


Acronym Name Studies


Name Type Data Collection Events Variables
Last Update: 2020-02-05 16:07