Psychological Medicine

Original Articles

The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): socio-demographic correlates, reliability, validity and some norms

A. F. Jorma1 c1 and P. A. Jacomba1

a1 NH & MRC Social Psychiatry Research Unit, The Australian National University, Canberra, Australia

Abstract

The IQCODE is a questionnaire which asks an informant about changes in an elderly person's everyday cognitive function. The questionnaire aims to assess cognitive decline independent of pre-morbid ability. In the present study, the IQCODE was administered to a sample of 613 informants from the general population. In addition, the questionnaire was administered to informants of 309 dementing subjects who had filled it out one year previously. A principal components analysis, using the general population sample, confirmed that the IQCODE measures a general factor of cognitive decline. The questionnaire was found to have high internal reliability in the general population sample (alpha = 0·95) and reasonably high test-retest reliability over one year in the dementing sample (r = 0·75). The total IQCODE score, as well as each of the 26-items, was found to discriminate well between the general population and dementing samples. The correlation with education was quite small (r = – 0·13), indicating that contamination by premorbid ability is not a problem.

Correspondence:

c1 Address for correspondence: Dr A. F. Jorm, NH & MRC Social Psychiatry Research Unit, The Australian National University, Canberra, ACT, 2601, Australia.

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