Multiple sclerosis, also known as MS, is a chronic disease that attacks the central nervous system, i.e. the brain, spinal cord and optic nerves. In severe cases, the patient becomes paralyzed or blind while in milder cases there may be numbness in the limbs.
Over 350,000 people have MS in the US. The Cleveland Clinic says that MS-related health care costs are thought to be over $10 billion per year in the US.
According to the British National Health Service, approximately 100,000 people live with multiple sclerosis in the UK. Symptoms usually appear between 15 and 45 years of age. Women are twice as likely to get MS than men.
Contents of this article:
Fast facts on multiple sclerosis
Here are some key points about multiple sclerosis. More detail and supporting information is in the main article.
- More than 350,000 Americans have MS
- Multiple sclerosis attacks the central nervous system
- The myelin sheath of MS patient's nerves is steadily degraded
- Multiple sclerosis can affect people of all ages
- Women are more commonly affected by MS than men
- Multiple sclerosis is more common the further a population lives from the equator
- Many believe MS is an autoimmune disease
- A genetic predisposition is involved in MS
- Month of birth appears to be a factor in the development of MS
- Diagnosis of multiple sclerosis is still a difficult process.
What is multiple sclerosis?
MS degrades the nerve's myelin sheaths.
The term multiple sclerosis comes from the Latin multus plus plica meaning "fold", and the Greek sklerosis meaning "hardening".
With multiple sclerosis, the central nervous system (CNS) is attacked by the person's own immune system. That is why MS is known as an auto-immune disease.
Nerve fibers are surrounded by myelin, which protects them. Myelin also helps conduct electrical signals (impulses) - i.e. myelin facilitates a good flow of electricity along the nervous system from the brain. Myelin regulates a key protein involved in sending long-distant signals.
The myelin of a patient with MS disappears in multiple areas. This leaves a scar (sclerosis). Multiple sclerosis means "scar tissue in multiple areas." The areas where there is either not enough or no myelin are called plaques or lesions. As the lesions get worse the nerve fiber can break or become damaged.
When a nerve fiber has less myelin the electrical impulses received from the brain do not flow smoothly to the target nerve - when there is no myelin the nerve fibers cannot conduct the electrical impulses at all. The electrical impulses are instructions from the brain to carry out actions, such as to move a muscle. With MS, you cannot get your body to do what your brain wants it to do.
Risk factors for multiple sclerosis:
- Multiple sclerosis can affect people of all ages
- It is more common among people aged from 20 to 50 years
- More women develop MS than men
- People of European descent are more likely to develop MS, compared to other people. However, people of all ancestries can get it
- You can inherit a greater susceptibility of getting MS from your parents
- In 2007, the World Health Organization (WHO) estimated that approximately 2.5 million people had multiple sclerosis
- Multiple sclerosis rates are higher the further away you live from the equator. This leads many to believe that exposure to sunlight impacts on MS risk.
Causes of multiple sclerosis
Although experts are still uncertain, most of them say that the person's own immune system attacks the myelin as if it were an undesirable foreign body - in the same way our immune system might attack a virus or bacteria.
Why might our immune system attack the myelin?
The reasons could be:
- Genetic - some studies have shown that the genes we inherit from our parents may, in part, impact on our risk of developing multiple sclerosis. If you have a parent, sibling, or grandparent who has/had MS, your risk of developing it yourself is greater than average.
Several genes are most likely involved in influencing multiple sclerosis risk, experts say. Scientists believe that a set of gene variants we are born with, plus exposure to some environmental trigger(s), affect the immune system of some people which eventually leads to MS symptoms.
We are probably not that far from identifying those gene variants. The largest multiple sclerosis genetic study ever undertaken, involving 250 scientists from around the world and led by the Universities of Cambridge and Oxford, reported in the journal Nature in August 2011 that over 50 genes had been identified and associated with MS
- Environmental - MS prevalence varies according to geographical area and population groups. Multiple sclerosis is much more common in northern Europe than southern Europe, northern USA than southern USA.
It seems that the more exposure to sunlight we have, the lower our MS risk is.
Italian scientists explained in July 2012 at the 22nd Meeting of the European Neurological Society (ENS) in Prague, Czech Republic, that people with high vitamin D levels are less likely to develop MS
In the USA, white people have a higher risk of developing multiple sclerosis than other racial groups; regardless of geographical location.
Studies indicate that people who move from a higher-risk area to a lower-risk one only acquire the risk of the new area if they move before they reach adolescence. This means that there is something in the environment we are exposed to early in life which influences risk.
Exposure to a toxic substance, such as a heavy metal or solvent has been suggested, but no clear conclusions have been reached.
People with MS are less likely to suffer from gout. MS patients have lower-than-average levels of uric acid in their system, which leads scientists to believe that uric acid protects from multiple sclerosis
It is unlikely there is just one trigger, experts say, but rather multiple sclerosis is probably triggered by multiple factors.
- Infections - doctors and researchers have often mentioned viruses, such as Epstein-Barr (mononucleosis), varicella zoster, as possible MS triggers; however, this theory has not been backed up scientifically
- Too much salt - too much salt may trigger the immune system, causing autoimmune diseases, researchers from the Massachusetts Institute of Technology reported in the journal Nature (March 2013 issue). The excessive consumption of salt might increase our risk of developing multiple sclerosis.
Sunlight and Vitamin D appear to play a role in MS.
Does your birth month influence your multiple sclerosis risk?
Scientists found that English babies born in May have lower levels of vitamin D and higher levels of autoreactive T-cells compared to those born in November. Vitamin D and T-cell levels influence a person's risk of developing autoimmune diseases such as multiple sclerosis.
The researchers, from Queen Mary, University of London and the University of Oxford, explained in the journal JAMA Neurology (April 2013 issue) that their study gives a possible biological platform as to why a human's risk of developing MS is impacted by the month they were born.
Co-author Dr. Sreeram Ramagopalan, said:
"By showing that month of birth has a measurable impact on in utero immune system development, this study provides a potential biological explanation for the widely observed "month of birth" effect in MS. Higher levels of autoreactive T-cells, which have the ability to turn on the body, could explain why babies born in May are at a higher risk of developing MS.
The correlation with vitamin D suggests this could be the driver of this effect. There is a need for long-term studies to assess the effect of vitamin D supplementation in pregnant women and the subsequent impact on immune system development and risk of MS and other autoimmune diseases."
On the next page, we look at the symptoms and diagnosis of multiple sclerosis.