Prospective memory — the ability to remember to carry out a future task — is significantly impaired in multiple sclerosis (MS) patients, and may contribute to worse cognitive performance for everyday tasks, according to recent research.
Cognitive impairment has been reported extensively in MS patients, and research indicates that memory deficits can be a contributing factor. Researchers estimate that 40–65% of MS patients experience objective memory impairment.
However, most studies have examined retrospective memory, which is the capacity to recall past information. Recent studies in other diseases, such as Parkinson’s disease, have indicated that deterioration of prospective memory is linked to poor everyday functioning.
In MS, researchers have found that self-reported prospective memory loss correlates with the risk of unemployment, pointing to a possible association between that memory impairment and cognitive deficits.
Prospective memory comprises two types of memory: time-based and event-based. Time-based prospective memory refers to tasks in which time is monitored to perform a future intention — for example remembering to call a friend in two hours. In event-based prospective memory, the cue to remember comes from the environment — for example remembering to mail a letter when you drive by the post office.
To explore whether MS patients experience difficulties in this “remembering to remember” type of memory, and how that is linked to cognitive performance, a team from the Kessler Foundation in New Jersey compared memory and functional performance between MS patients and a group of healthy people (controls).
Researchers evaluated 30 MS patients and 30 healthy controls, ages 28–65.
Results showed that MS patients overall performed worse in the MIST test, but only time-prospective memory (not event-based) was significantly impaired relative to the control group.
Researchers also found that a longer cue-intention delay was relevant for a worse performance. For instance, MS patients performed significantly worse at remembering tasks with a 15-minute delay compared to a two-minute delay.
“These results suggest that Time-PM [prospective memory] is disproportionately impaired relative to Event-PM in MS, and that these effects are exacerbated by longer delays” they wrote.
By comparing MIST and AR test results, the team observed that time-based MIST subclasses were linked to poor measures of overall performance, performance errors, and time to completion. Moreover, deficits in time-based prospective memory were associated with poorer executive function and worse motor scores, which may reflect a link between this memory impairment and MS disease severity.
“Poor prospective memory hinders the ability to perform a broad range of everyday life activities, which undermines individuals’ independence,” Erica Weber, PhD, the study’s lead author, said in a press release.
“Our findings indicate that developing strategies that improve time-based functioning may help individuals with MS improve their prospective memory, and support their efforts to maintain their independence,” she added.