Cognitive impairment affects 40-65% of people with MS. Why? In the past year, a number of studies have helped us build a better picture of the precise nature of cognitive problems that may affect multiple sclerosis sufferers:
Cognitive decline is common in those with multiple sclerosis, but not everyone is so afflicted. What governs whether an individual will suffer cognitive impairment? One proposed factor is cognitive reserve, and a new study adds to the evidence that cognitive reserve does indeed help protect against cognitive decline, as it does with age-related decline.
A study involving 187 children and adolescents with multiple sclerosis, plus 44 who experienced their first neurologic episode (clinically isolated syndrome) indicative of MS, has found that 35% of those with MS and 18% of those with clinically isolated syndrome were cognitively impaired. Cognitive assessment was done using a battery of 11 tests. The most common areas of impairment were fine motor coordination, visual-motor integration, and speeded information processing.
Problems with myelin — demyelination (seen most dramatically in MS, but also in other forms of neurodegeneration, including normal aging and depression); failure to develop sufficient myelin (in children and adolescents) — are increasingly being implicated in a wide range of disorders. A new animal study adds to that evidence by showing that social isolation brings about both depression and loss of myelin.
It’s estimated that 43%-70% of those with multiple sclerosis suffer from some level of cognitive impairment (yes, a very broad range! perhaps the finding of this study offers one clue why). Most commonly, this is seen in slower processing speed, impaired memory, impaired executive function, and poorer visuospatial processing. There are a number of factors that have been implicated in why some people suffer from cognitive impairment and others don’t, such as age of onset and male gender. As with dementia, depression also may be a factor, while cognitive reserve appears protective.
Multiple sclerosis typically starts in young adulthood, but about 5% start in childhood or adolescence. A study of 63 children under age 18 with MS has found that they more likely to have low IQ scores than healthy controls. Five of the children with MS had IQ scores of less than 70 (none of the controls did), 15 had IQ scores between 70 and 89 (compared to two of the controls), and 31% of the MS children met the criteria for cognitive impairment compared to less than 5% of the controls. Low IQs were correlated with younger age at onset. About 30% of the children with MS also had language difficulties, which is not common in adults with MS. It may be that children are particularly vulnerable to the effects of MS because their brain is still developing.
Lopez, M., Patti, F., Vecchio, R., Pozzilli, C., Bianchi, V., Roscio, M., … De Caro, M. F. (2008). Cognitive and psychosocial features of childhood and juvenile MS. Neurology, 70(20), 1891-1897. Retrieved from http://www.neurology.org/cgi/content/abstract/70/20/1891
http://www.eurekalert.org/pub_releases/2008-05/aaon-mca050608.php
A study of 140 Canadians with multiple sclerosis has found that those (10) who were defined as current marijuana users performed 50% slower on tests of information processing speed compared to matched MS patients who did not smoke marijuana. There was also a significant association between smoking marijuana and emotional problems such as depression and anxiety.
Ghaffar, O., & Feinstein, A. (2008). Multiple sclerosis and cannabis. A cognitive and psychiatric study. Neurology, 01.wnl.0000304046.23960.25 - 01.wnl.0000304046.23960.25. Retrieved from http://www.neurology.org/cgi/content/abstract/01.wnl.0000304046.23960.25v1
http://www.eurekalert.org/pub_releases/2008-02/aaon-smi020508.php
New research has revealed a previously unknown mechanism by which brain cells can be damaged during chronic neurodegenerative diseases such as Alzheimer's, multiple sclerosis, Parkinson's and dementia associated with HIV. When inflammation occurs in the brain, nerve impulses can become toxic. Instead of triggering the formation of memories, these impulses can inflict injury on neurons and disrupt neural function. Understanding this mechanism could provide a new path for drugs to treat the diseases, perhaps by chemical preconditioning to induce adaptations in nerve cells that would enable the cells to better withstand toxic attacks, prevent injury, and preserve function.
Bellizzi, M. J. (2005). Synaptic activity becomes excitotoxic in neurons exposed to elevated levels of platelet-activating factor. Journal of Clinical Investigation, 115(11), 3185-3192. Retrieved from http://www.jci.org/cgi/doi/10.1172/JCI25444
http://www.eurekalert.org/pub_releases/2005-11/uorm-ssh110305.php
A study of 39 MS patients found that those receiving ginkgo biloba were about 13% faster on a Stroop test (measures a person's ability to pay attention and to sort conflicting information). Such a difference would be comparable to differences in scores between healthy people ages 30 to 39 and those ages 50 to 59. The benefit appeared to be greatest for those who had certain problems with the Stroop test.
The study was presented at the American Academy of Neurology's 57th Annual Meeting in Miami Beach, Fla.
http://www.eurekalert.org/pub_releases/2005-04/ohs-osf042705.php
An estimated 50% of multiple sclerosis patients suffer some degree of cognitive impairment. A pilot study suggests that donepezil, a drug widely used for treating dementia in Alzheimer's patients, may improve memory and cognition in MS patients who are mild to moderately cognitively impaired. The trial involved 69 MS patients. Over 65% of those given donepezil showed cognitive improvement, compared to 32% of those receiving a placebo.
The study was presented by Laura Krupp at the American Academy of Neurology 56th Annual Meeting in San Francisco, Calif., on April 27.
http://www.eurekalert.org/pub_releases/2004-04/aaon-adi042004.php
A six-month double-blind, placebo-controlled pilot study of 23 individuals with mild multiple sclerosis found that patients who took the herb Ginkgo biloba performed better on neuropsychological tests compared to those who took the inactive placebo.
Corey-Bloom, J., Kenney, C. & Norman, M. 2002. Paper presented at the annual meeting of the American Academy of Neurology on April 18 in Denver, Colorado.
http://www.eurekalert.org/pub_releases/2002-04/uoc--gbs041202.php
Cognitive problems affect up to 60% of patients with multiple sclerosis. Treatment of MS has until now paid little attention to this aspect of the disease. A preliminary study of 17 patients with advanced MS and severe cognitive impairment found that a drug currently used to treat mild to moderate dementia from Alzheimer’s disease was noticeably effective in improving the cognitive functioning in many of the MS patients. A study of 240 patients at 21 hospitals and medical centers is now about to commence.
http://www.eurekalert.org/pub_releases/2001-06/UoRM-Dtmd-1706101.php
People who suffer from cognitive difficulties related to Multiple Sclerosis (MS) may have a slower driving reaction time and increased risk of accidents. The study compared 13 people with MS who exhibited cognitive difficulties, 15 people with MS who did not exhibit cognitive difficulties, and 17 people without MS. Based on two computerized driving tests, those with MS who exhibited cognitive difficulties had a slower response time by 1,721 milliseconds than the other MS participants. In addition, 29 percent of these people tested as high risk for accident involvement.
Schultheis, M. T., Garay, E., & DeLuca, J. (2001). The influence of cognitive impairment on driving performance in multiple sclerosis. Neurology, 56(8), 1089-1094. Retrieved from http://www.neurology.org/content/56/8/1089.abstract
http://www.eurekalert.org/pub_releases/2001-04/AAoN-Daai-2304101.php
A study involving 50 people with MS (aged 18-65), of whom half used marijuana for pain relief, has found that marijuana users performed significantly worse on tests of attention, speed of thinking, executive function and visual perception of spatial relationships between objects. Those who used marijuana were also twice as likely as non-users to be classified as globally cognitively impaired.
Memory and learning problems often occur in multiple sclerosis, but bewilderingly, are only weakly associated with the severity of the disease. A study involving 44 people around the age of 45 who had MS for an average of 11 years has found that those with a mentally active lifestyle had good scores on the tests of learning and memory even if they had higher amounts of brain damage. The findings suggest that, as with Alzheimer’s disease, 'cognitive reserve' protects against cognitive impairment.
A study involving 236 persons with multiple sclerosis has found that only 7% of those with secondary-progressive MS showed sufficient vitamin D in their blood, compared to 18.3% of patients with the less severe relapsing-remitting type, and that higher levels of vitamin D3 and its byproducts were associated with better scores on cognitive tests (especially reasoning and planning), and less brain atrophy and fewer brain lesions. Lower-than-normal vitamin D status is known to be associated with a higher risk of developing MS