Review study links physical disability to cognitive problems in MS
Correlation between body and mind strengthens in advanced stages
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Greater physical disability is associated with poorer cognitive performance in people with multiple sclerosis, particularly in those with more advanced disability, according to a large review.
- Greater physical disability is strongly associated with poorer cognitive performance in people with multiple sclerosis, a review found.
- This is particularly true at advanced disease stages, though cognitive difficulties can also occur in patients with mild physical impairment.
- Experts recommend integrating cognitive evaluations with traditional mobility measures to improve disease monitoring and patient care.
Greater physical disability is associated with poorer cognitive performance in people with multiple sclerosis (MS), particularly in those with more advanced disability, according to a large review and meta-analysis.
However, cognitive difficulties may also occur in patients with mild physical impairment, and go undetected by conventional disability assessments.
“Cognitive and physical disabilities in MS are interdependent, particularly in the advanced stages of the disease,” researchers wrote.
The study, “Cognitive Function and Disability in People with Multiple Sclerosis: A Systematic Review and Meta-Analysis,” was published in the journal Neuropsychology Review.
Cognitive function in MS poorly captured by disability rating scales
MS is a chronic inflammatory disease that damages the brain and spinal cord, causing symptoms that include muscle weakness, walking difficulties, and problems with memory, attention, and information processing. Cognitive impairment affects an estimated 40% to 65% of people with MS and can emerge early in the disease.
“Although it has a high prevalence and significant impact, cognitive function is poorly captured by conventional disability rating scales in PwMS [people with MS],” the researchers wrote.
The most commonly used disability measure in MS is the validated Expanded Disability Status Scale (EDSS). However, the scale does not adequately capture cognitive difficulties. As a result, someone experiencing problems with thinking or memory may still receive a relatively low EDSS score if their mobility is largely preserved, “leading to an inaccurate representation of their overall disability burden,” the researchers wrote.
Past research examining the relationship between cognitive impairment and physical disability have led to inconsistent conclusions.
Higher disability scores linked to poorer performance on cognitive tests
In this study, a team of researchers set out to better understand this association and determine whether the onset and course of cognitive and physical disability align or diverge over time in MS patients.
To do so, they systematically analyzed published studies reporting on the association between cognitive function and disability among people living with MS. A total of 223 studies, covering 300,911 MS patients (mean age, 46.4 years; 72.15% women), were included in the final analysis. The majority of studies were conducted in Italy and the U.S.
Participants had lived with the disease for a mean of 9.2 years, and had a mean EDSS score of 2.2, indicating mild disability, with no walking problems.
Of these studies, 93 had data suitable for a meta-analysis, which statistically combines findings from multiple studies.
Physical disability was predominantly assessed using the EDSS, while cognitive function was mainly evaluated using the Symbol Digit Modalities Test (SDMT), which measures how quickly people process information. Other cognitive tests included the Mini-Mental State Examination and Montreal Cognitive Assessment, which evaluate a broader range of thinking skills.
Pooled data showed that higher EDSS scores were significantly associated with poorer performance on all three cognitive tests.
It must be acknowledged that the correlations found may not reflect a direct relationship between physical and cognitive disability.
The largest analysis of a single cognitive test, drawing on 65 studies involving 7,823 patients, examined the association between EDSS and SDMT scores. Poorer performance on the SDMT was also significantly linked to greater difficulties on validated tests assessing hand coordination and walking, as well as greater disability reported by patients themselves.
Subgroup analyses showed that the association between physical disability and poorer cognitive performance was stronger in people with more advanced disability than in those with milder physical impairment. Age, disease duration, and MS type did not significantly change the strength of these associations.
Among the study limitations are differences in how studies were conducted and which measures were used, as well as concerns about participant selection. Furthermore, factors known to independently affect both cognitive performance and disability, including mood and fatigue, “were not accounted for … because they were inconsistently reported across the included studies,” the researchers wrote.
“Therefore, it must be acknowledged that the correlations found may not reflect a direct relationship between physical and cognitive disability,” they added.
Nevertheless, these results suggest that relying on physical disability measures alone may underestimate the overall burden of MS, particularly during earlier disease stages when cognitive problems may develop independently of mobility limitations.
“Redefining MS disability in a multidimensional framework, integrating cognition, fatigue, and upper limb function with traditional mobility measures” could improve disability monitoring, enable earlier identification of cognitive difficulties, and support more individualized patient care, the researchers concluded.
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