The utility of a non-verbal prospective memory measure as a sensitive marker for early-stage Alzheimer's disease in Hong Kong

Time-Based and Event-Based Prospective Memory in Mild Cognitive Impairment and Alzheimer's Disease Patients: A Systematic Review and Meta-analysis

Prospective memory (PM) is the ability to remember to perform planned actions in a future moment and it is of fundamental importance for an independent and autonomous lifestyle from development to late adulthood. Deficits in episodic memory and executive functions, which are involved in PM are characteristic features of mild cognitive impairment (MCI) and Alzheimer's disease (AD). Considering that the number of older adults is drastically increasing over the next decades, it is of great interest to understand how PM decline in healthy older adults and patients with different degree of cognitive decline. The present meta-analysis included 46 studies investigating PM performance in AD patients (17 studies) and people with MCI (24 studies); 5 studies included both clinical conditions in the same article. The 46 studies contributed a total of 63 independent samples and 129 effect sizes from 4668 participants (2115 patients and 2553 controls). Unlike previous reviews of the literature, our results with a larger and updated sample of studies confirmed lower PM abilities in AD compared to MCI and controls, although we did not observe conclusive differences between event-based and time-based PM in patients. Surprisingly, PM deficits shown by MCI and AD patients have decreased across years, in parallel to a reduction of the evidence of publication bias and an increase in the number of observations per task. We propose the use of more reliable research designs as one plausible explanation for the reduction of PM impairments.

The Measurement of Everyday Cognition (ECog): Revisions and Updates

INTRODUCTION

The Everyday Cognition scale (ECog), a measure of everyday functioning developed in 2008, is sensitive to early detection and progression of neurodegenerative disease. The goal was to update ECog item content to ensure relevancy to contemporary older adults from diverse backgrounds.

METHODS

Participants included 44 culturally diverse older adults (18 with normal cognition, 11 with mild cognitive impairment) and their study partners. Item understandability and relevance was evaluated using iterative interviewing methods that were analyzed using standard qualitative methods. On the basis of this information, items were modified, deleted, or developed as needed.

RESULTS

Of the 39 original items, 19 were revised, 3 new items were added (primarily to cover contemporary activities such as the use of technology), and 1 was deleted. The revised version (ECog-II) includes 41 items.

DISCUSSION

To ensure strong psychometric properties, and to facilitate harmonization of previously collected data, we preserved well over half of the items. Future work will validate the revised ECog by measuring associations with neuropsychological performance, external measures of disease, and other functional measures. Overall, the revised ECog will continue to be a useful tool for measuring cognitively relevant everyday abilities in clinical settings and intervention clinical trials.

Improving Prospective Memory in Healthy Older Adults and Individuals with Very Mild Alzheimer's Disease

OBJECTIVES

To test the utility of a memory-encoding strategy for improving prospective memory (PM), the ability to remember to execute future goals (e.g., remembering to take medications), which plays an important role in independent living in healthy older adults and those with very mild Alzheimer's disease (AD).

DESIGN

Participants were randomly assigned to an encoding strategy condition or a standard encoding condition.

SETTING

A longitudinal study conducted at an Alzheimer's disease research center. Testing took place at the center and in a university testing room.

PARTICIPANTS

Healthy older adults (Clinical Dementia Rating (CDR) = 0.0, n = 38) and those classified as being in the very mild stage of AD (CDR = 0.5, n = 34).

INTERVENTION

A simple strategy ("If I see Cue X, then I will perform Intention Y") was used to strengthen PM encoding and reduce the probability of forgetting to execute one's future plans.

MEASUREMENTS

PM was assessed using Virtual Week, a laboratory task that requires the simulation of common PM tasks (the types of tasks performed in everyday life), such as taking one's medication at breakfast.

RESULTS

The encoding strategy significantly reduced PM failures in healthy older adults and those with very mild AD and was effective regardless of the individual's episodic memory ability.

CONCLUSION

This encoding strategy was successful in reducing PM errors in healthy older adults and those with mild AD with a range of memory abilities.

An implementation intention strategy can improve prospective memory in older adults with very mild Alzheimer's disease

OBJECTIVES

This study tested whether (1) very mild Alzheimer's disease (AD) is associated with impaired prospective memory (PM) for tasks that are supported by either spontaneous retrieval (focal PM) or strategic monitoring (non-focal PM) and (2) implementation intention (II) encoding could improve PM performance in very mild AD.

DESIGN

Thirty-eight healthy older adults and 34 with very mild AD were randomly assigned to perform two PM tasks in either the standard or the II encoding condition.

METHOD

All participants performed blocks of category decision in which they were asked to respond to a focal PM target (e.g., the word 'orange') and a non-focal PM target (e.g., words that begin with the letter 'o'). Half of the participants encoded PM instructions in the standard manner, while the other half had a stronger encoding by forming IIs. PM accuracy and category decision accuracy and reaction times were measured.

RESULTS

Participants with very mild AD showed deficits in both focal and non-focal PM performance compared to the healthy controls, reflecting deficits in both spontaneous retrieval and strategic monitoring. Participants with very mild AD in the II encoding condition showed better focal PM performance relative to those in the standard encoding condition.

CONCLUSIONS

Deficits in both focal and non-focal PM are associated with very mild AD and IIs may be a helpful behavioural intervention for the focal PM deficits.

PRACTITIONER POINTS

Multiple deficits in PM are observable in very mild AD. Implementation intentions may enhance focal PM in very mild AD. Future research using larger samples is needed to better understand the effect of II on non-focal PM tasks in healthy older adults and those with very mild AD. The use of simple laboratory PM tasks may limit the generality of our findings. Future research is needed to investigate whether IIs improve PM over a range of more realistic tasks.