Extended retention intervals can help to bridge the gap between subjective and objective memory impairment

Despite their excellent clinical validity, objective measures of memory often do not reflect self-perceived memory impairment. This discordance has mostly been attributed to depressed mood. Alternatively, a lack of ecological validity due to the rather short standard retention intervals of 20-60 min may be responsible for this discordance. Therefore, we explored the value of extended retention intervals in regard to subjective memory deficits.

Our prospective study was based on 73 patients with epilepsy. In addition to the standard 30-min retention interval of a verbal learning and memory test (VLMT) patients were randomized to either a free delayed recall after 1 week or after 4 weeks. Mood was assessed by the Beck Depression Inventory (BDI).

Forty-four patients (60%) reported self-perceived memory deficits, whereas objective verbal memory impairment was present in 26 patients (36%). Concordance between subjective and objective memory performance was observed in 53% of the patients. Multivariate analyses identified memory performance after 4 weeks and self-rated mood as determinants of subjective memory impairment. Self-perceived memory impairment correlated with the number of remembered words after 4 weeks (r = -0.361, p = 0.030) and the BDI total score (r = 0.332, p = 0.004) but neither with recall performance after 30 min nor after 1 week.

Subjective memory appears to follow a different time scale than routine memory testing. Thus, the introduction of longer retention intervals may enhance the ecological validity of standard memory tests. Furthermore, the findings again underscore that controlling for mood is mandatory when dealing with subjective memory complaints.