Remember to buy milk on the way home! A meta-analytic review of prospective memory in mild cognitive impairment and dementia.

Prospective memory (PM) is the ability to remember to execute delayed intentions. Previous studies indicate that PM is impaired in persons with mild cognitive impairment (MCI) and dementia, but the extent, nature, and cognitive correlates are unclear. A meta-analytic review was, therefore, performed (literature search 1990 to July 2011) on case-control studies on PM in dementia (10 studies, 336 patients, 505 controls) and MCI (7 studies, 225 patients, 253 controls). Differences between event-based and time-based PM and between measures of prospective and retrospective memory were examined, as well as correlations with other cognitive functions. Results showed that patients with dementia or MCI exhibit large deficits in PM (Hedges' d -1.62 [95% confidence interval -1.98 to -1.27; p < .0001] for dementia; -1.24 [-1.51 to -0.995; p < .0001] for MCI; difference dementia vs. MCI: QM = 1.94, p = .16). Impairments were comparable in size for event-based and time-based PM (p > .05), as well as for prospective and retrospective memory (p > .05). PM showed modest correlations with measures of retrospective memory (median r = 0.27) and executive functioning (median r = 0.30). PM appears a valid construct in neuropsychological assessment in patients with dementia or MCI, but more insight is needed in the optimal characteristics of PM tasks to be used in clinical practice.