How valid are subjective ratings of prospective memory in mild cognitive impairment and early dementia?

BACKGROUND

Prospective memory refers to memory for future intentions and is a critical predictor of functional capacity in late adulthood. For many other cognitive abilities, self- and informant-rated methods of assessment are routinely used to guide clinical decision-making. However, little is known about the validity (and consequently the clinical utility) of subjective reports of prospective memory difficulties.

OBJECTIVE

The aim of this study was to compare clinical [mild cognitive impairment (MCI), dementia] and nonclinical older adults (healthy controls) on self- and informant-rated versions of prospective and retrospective memory function, as well as objective measures of prospective memory. Critical here was not only the assessment of between-group differences, but also whether these different methods of assessing memory function would show appropriate convergent and discriminant validity.

METHODS

A total of 138 participants aged between 64 and 92 years, diagnosed with dementia (n=37), MCI (n=48) or no impairment (n=53), were asked to complete self- and informant-rated versions of the Prospective and Retrospective Memory Questionnaire (PRMQ). Participants also completed behavioural measures of global cognitive function [the Mini-Mental State Examination (MMSE)], as well as a behavioural measure of prospective memory (Virtual Week).

RESULTS

Self-reported impairments were equivalent across the three groups, and informant reports of impairment, while higher for those with dementia, did not distinguish MCI from controls. For the combined sample and for all three groups separately, both self- and informant reports of prospective memory showed poor convergent validity, at best correlating only weakly with Virtual Week. Self-reported prospective memory was correlated with informant report only in the dementia group, not in the control or MCI groups. Convergent and discriminant validity were poor, with self- and informant-rated prospective memory more strongly related to self- and informant-rated retrospective memory than to scores on Virtual Week.

CONCLUSION

These data indicate that self-report and informant report may neither accurately measure prospective memory of older people, nor be sensitive to objective prospective memory difficulties in people with MCI and dementia. These data have potentially important implications for clinical practice.