Informant Questionnaire of Cognitive Decline in The Elderly (IQCODE)

Informant Questionnaire of Cognitive Decline in The Elderly (IQCODE)

LASA filenames:
LASA607
LASAC707

Contact: Almar Kok

Background
Loss-to-follow up is among others associated with cognitive decline. Persons who become demented are for instance no longer able to participate in the study. To obtain an impression of possible cognitive decline or dementia from the persons that are no longer able to participate in the study, we ask the proxy some questions about cognitive functioning of their relative.

Measurement instruments in LASA
The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE; Jorm & Jacomb, 1989) is a short questionnaire designed to assess cognitive decline and dementia in older persons. The original form contains 26 items, a shortened 16 question form of the IQCODE has also been validated (Jorm, 1994).

In LASA, an adapted form of the IQCODE was used and included 6 questions concerning decline in the last 10 years, namely: remembering conversations; remembering his/her address and phone number; handling known domestic appliances; making decisions on everyday affairs; handling money for groceries; handling finances. The questions were scored on a 5-point scale: 1=much better, 3=unchanged, 5 = much worse.

Scale construction
The scale is based on a sum score of answers to the six items, resulting in a score ranging from 6 to 30, higher scores indicating more cognitive decline. If one item was missing, the mean score of the remaining five items was added to the sum score based on the five non-missing items. If two items were missing, the mean score of the remaining four items was added twice to the sum score based on the four non-missing items. If more than two items were missing, no scale score was computed.

The IQCODE was administered once (at C) by phone to respondents who could or would not participate in the complete interview, and from wave C on administered by phone to the proxy of the respondent who could or would not participate in the complete interview.

Questionnaires
LASAC607 / LASAD607 / LASAE607 / LASAF607 / LASAG607 / LASAH607 / LASAI607 / LASAJ607 / LASAK607 (telephone interview with proxy, in Dutch)
LASAC707 (telephone interview with respondent, in Dutch)

Variable information
LASAC607 / LASAD607 / LASAE607 / LASAF607 / LASAG607 / LASAH607 / LASAI607 / LASAJ607 / LASAK607
(pdf);
LASAC707
(pdf)

Availability of information per wave ¹

¹ More information about the LASA data collection waves is available here.

* 2B=baseline second cohort;
3B=baseline third cohort;
MB=migrants: baseline first cohort

Tr=data collected in telephone interview with respondent;
Tp=data collected in telephone interview with proxy

Previous use in LASA
The IQCODE is used in a composed variable comprising persons with a probable dementia diagnosis (see probable dementia). This variable is used in a paper that aimed to develop classification models for use in primary care to aid early identification of persons at risk for persistent cognitive decline (Van den Kommer et al 2008).

References

1. Jorm AF, Jacomb PA. The Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): socio-demographic correlates, reliability, validity and some norms. Psychol Med. 1989 Nov;19(4):1015-22.
2. Jorm AF. A short form of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE): development and cross-validation. Psychol Med. 1994 Feb;24(1):145-53.
3. Van den Kommer TN, Comijs HC, Dik MG, Jonker C, & Deeg DJH. Development of classification models for early identification of persons at risk for persistent cognitive decline. Journal of Neurology, 2008, 255(10): 1486-94.

Date of last update: December, 2019