Beliefs About Dementia: Development and Validation of the Representations and Adjustment to Dementia Index (RADIX)

Catherine Quinn, Robin G. Morris, Linda Clare

Research output: Contribution to journalArticlepeer-review

23 Citations (Scopus)


Objectives The Self-Regulation Model (SRM) identifies that the beliefs people hold about an illness can influence their responses to that illness. Whilst there are generic measures of illness representations, there is a need for a brief tailored measure to use with people with dementia. The aim of this study is to develop and validate a brief measure called the ‘Representations and Adjustment to Dementia Index’ (RADIX). The RADIX contains questions on the SRM elements: Identity, Cause, Timeline, Control, and Consequences. Method The RADIX validation was conducted with a sample of 385 community-dwelling people with mild to moderate dementia who were taking part in the IDEAL cohort study. Test-retest reliability was conducted over a 4-week period with a separate sample of 20 people with dementia. Results The validation process resulted in a reduction in the number of items in the Timeline, Control, and Consequences items. The resulting RADIX demonstrated good acceptability, internal reliability, and test-retest reliability. All the RADIX items had low missing data, indicating good acceptability. The factor analysis confirmed that the Consequences items formed two sub-scales, practical and emotional consequences, which had Cronbach's α of 8 and .91 respectively. Test-retest reliability indicated that the Identity, Timeline, and Control items had moderate reliability and the practical and emotional consequences scales had good reliability. Conclusion The RADIX demonstrates acceptable psychometric properties, proves to be a useful measure for exploring people's beliefs about dementia and could aid the provision of tailored information and support to people with dementia.
Original languageEnglish
JournalAmerican Journal of Geriatric Psychiatry
Early online date26 Feb 2018
Publication statusE-pub ahead of print - 26 Feb 2018


  • -WordsAlzheimer's
  • Illness Representations
  • Illness Perception
  • Questionnaire
  • Reliability
  • Validity


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