Validation analysis of informant's ratings of cognitive function in African Americans and Nigerians.

OBJECTIVES

To examine informant validity using the Community Screening Interview for Dementia (CSI 'D') both cross-sectionally and longitudinally in two very different cultures and to explore the effects of informants and study participants' characteristics on the validity of informants' reports.

METHODS

Elderly African Americans age 65 years and older residing in Indianapolis, USA and elderly Yoruba Nigerians age 65 years and older residing in Ibadan, Nigeria were assessed on cognitive functioning using the CSI 'D' at baseline (1992-1993) and five-year follow-up (1997-1998). At baseline, the informant validity in both samples was evaluated against participants' cognitive tests using Pearson correlation and regular regression models. At follow-up, informants ratings on cognitive decline were assessed against participants' cognitive decline scores from baseline to follow-up using biserial correlation and logistic regressions.

RESULTS

At baseline, informants' reports on cognitive functioning significantly correlated with cognitive scores in both samples (Indianapolis:r = -0.43, p < 0.001; Ibadan:r = -0.47, p < 0.001). The participant-informant relationships significantly affected the informants' reports in the two samples with different patterns (p = 0.005 for Indianapolis and p < 0.001 for Ibadan) at a given level of cognitive functioning. African Americans spouses reported more cognitive problems, while siblings reported more problems for the Yoruba Nigerians. At follow-up, informants' ratings on cognitive decline significantly correlated with the cognitive decline scores (Indianapolis r = 0.38, p < 0.001; Ibadan r = 0.32, p < 0.001). The characteristics of study participants and informants had little impact on the informants' ratings on cognitive decline.

CONCLUSIONS

Informant reports are valid in assessing the cognitive functioning of study participants both cross-sectionally and longitudinally in two very different cultures, languages and environments.