Inability to Multitask in MS Indicator of Depression Severity

Damian McNamara

April 30, 2018

LOS ANGELES — People with multiple sclerosis (MS) who have greater difficulty multitasking are more likely to have more severe depression, according to findings that suggest interventions to treat mood could improve cognition in this patient population.

In addition, investigators linked a lower ability to multitask to smaller volumes of the rostral prefrontal cortex (PFC), an area of the brain involved in higher-order executive functioning.

Both studies were presented here at the American Academy of Neurology (AAN) 2018 Annual Meeting.

Novel Assessment Tool

"MS patients with depression frequently report cognitive dysfunction. However, when we send them for neuropsychiatric evaluation, the results are often average or normal," said Daniel Kurz, MD, a fellow at the Corinne Goldsmith Dickinson Center for Multiple Sclerosis at the Icahn School of Medicine at Mount Sinai in New York City. "We thought perhaps current testing procedures do not accurately reflect the dysfunction and disability our patients are reporting."

As an alternative, Kurz and his team evaluated whether a new tool developed by colleague James Sumowski, MD, would offer better discrimination. They assessed 150 participants in the RESERVE Study of Early Multiple Sclerosis using Sumowski's Decision Speed Task.

Patients look at rows of four objects, represented by emojis, and choose the one that is the largest in real life. Investigators recorded the number of correct responses in 100 seconds for each participant.

Researchers next combined the Decision Speed Test with a simultaneous auditory task, one where participants had to note when they heard certain words (the one-back test). Again, they calculated performance based on the number of correct answers in 100 seconds. They adjusted results for factors including age, IQ, and education.

Higher depression scores on the Beck Depression Inventory, the Mental Health Index, and the Stroop task correlated with fewer correct answers. In addition, in a stepwise regression, they found "that multitasking was the only independent predictor of worse depression," Kurz said.

When researchers stratified patients by depression severity — none, mild, moderate, or severe — the relationship still held. Again, more severe depression correlated with fewer correctly identified objects on the multitasking evaluation, he said.

"We could look at this in the future to see if an intervention for depression could affect or improve cognitive impairment, which has been difficult to treat in MS patients."

Commenting on the findings for Medscape Medical News, poster discussion session moderator Nancy L. Sicotte, MD, director of the Multiple Sclerosis Program at Cedars-Sinai Medical Center in Los Angeles, California, said they are "clinically useful in the sense that what we hear from patients is that they are having a hard time with multitasking. And it makes sense because the disease is a white matter disease and that is what is connecting all the different areas of the brain. What their study is showing — and this is a bit different — is that this is also related to depression."

"We've done some work in our lab looking at the hippocampus, a very important cortical structure for memory as well as cognitive function," she said. "We know that depression is really common [and] we know that cognitive problems are very common, and we've shown that those come together in the hippocampus."

An unanswered question from the current research is whether MRI findings would show a correlation between brain structural changes and worse depression in patients with MS, she added.

Early Screen for MS?

Worse performance at multitasking was also associated with smaller volumes of the rostral PFC on three-dimensional T1 MRI, according to a separate poster presented at the AAN conference.

A smaller volume of the rostral PFC independently predicted worse multitasking performance (rp = 0.333; P < .0001). Rostral PFC volumes were also smaller among patients who were normatively impaired in multitasking compared with unimpaired participants (t [129] = 2.27; P = .025).

A lot of neurocognitive science literature attributes the PFC and the rostral portion in particular with higher-order functioning. This executive functioning includes tasks such as planning and divided attention, said Christina Lewis, BS, head research coordinator for the RESERVE Early MS Cohort at the Icahn School of Medicine at Mount Sinai.

"I was curious if our multitasking task, which is a very difficult task, had any correlation with our patients' gray matter in that area, and it did," she said.

A total 131 patients performed the primary task as fast and as accurately as they could, and then repeated it alongside a secondary auditory one-back task. "We looked at the difference in the accuracy scores, which I call the 'performance cost.' Basically, there was less performance cost the larger that Brodmann area 10 [also known as the rostral PFC] volume."

"People were definitely not able to perform as well if there was more than one thing going on," she said.

When asked whether the findings could contribute to an early screen for MS, she said, "That's the hope. One of the aims of the whole RESERVE study is looking at total gray matter volume as a potential biomarker."

Both studies were supported through National Institutes of Health grants. Kurz and Lewis have disclosed no relevant financial relationships.

American Academy of Neurology (AAN) 2018 Annual Meeting. Abstracts P4.196 and P5.028. Presented April 25 and 26, 2018.

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