Disproven Theories About the Causes of MS and Its Flare-ups
You may hear about a lot of potential causes of multiple sclerosis, the progressive, incurable disease that damages the brain, spinal cord and optic nerves. Theories have ranged from genetic to environmental triggers, some as simple as living with a pet.
In reality, it's difficult to say exactly what causes the condition. "If there were just one thing that caused MS, I believe we would have figured it out by now," says Dr. Robert Shin, a professor of neurology at MedStar Georgetown University Hospital.
[See: 9 Ways to Boost Your Immune System.]
Understanding MS
MS starts when the body's immune system mistakenly attacks the nerves and their protective covering. "I use the analogy of friendly fire. It's like we have soldiers in the field fighting the enemy. Sometimes they can get confused and accidentally shoot allies," Shin says.
The damage interrupts the signals being transmitted throughout the body, resulting in symptoms ranging from numbness and tingling in the extremities to vision problems, muscle weakness, trouble walking and even paralysis.
The disabling nature of the condition has motivated scientists to try to pinpoint why the immune system takes aim at a healthy central nervous system. Researchers are also seeking to understand what causes people with the most common type of MS -- called relapsing-remitting MS -- to experience symptom flare-ups periodically.
Eliminating MS Causes
It was only the 1960s when scientists began unraveling how the MS disease process works, according to the National Institutes of Health. In the six decades since, researchers have studied many potential causes of MS, and come up with few answers.
Scientists are at least beginning to understand what doesn't lead to MS onset. For example, scientists suspected for years that a virus carried by dogs, called canine distemper, was associated with the onset of MS in dog owners. A 1982 New York Times article recounts how two neurologists made the connection after three sisters developed MS in 1974, not long after the family's dog contracted distemper.
But there has not been enough clinical evidence to support a link between MS and canine distemper, reports the National Multiple Sclerosis Society.
The group notes that there is also a lack of evidence supporting an association between MS and:
-- Environmental allergens (allergies).
-- Exposure to the heavy metals mercury, lead or manganese.
-- Consumption of the artificial sweetener aspartame.
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Nixed Relapse Triggers
When Dr. Colin Bamford began researching MS in 1976, scientists already knew the immune system was involved in the development of MS. But it wasn't clear what triggered MS relapses or the progression of disability.
One question, Bamford recalls, was whether physical trauma could lead to deterioration. "There was even a hypothesis put forward that the more trivial the physical trauma, the more likely it would exacerbate MS. The patient might have been involved in a minor fender bender. But how far do you take that? A breeze? A ping-pong ball?" says Bamford, a neurologist at Banner-University Medical Center in Tucson, Arizona.
Research conducted by Bamford and his colleagues at the University of Arizona, published in 1991, suggested there was no association between mild to moderate physical trauma and MS relapses or progression of disability. Similar studies supported the findings. "I'm comfortable in saying we've eliminated mild and moderate trauma as a cause of deterioration. But we did not get a clear answer about whether severe injuries to certain parts of the brain could have a negative impact," he says. "We didn't have it then, and we don't have it now."
He says the observational nature of recording relapse triggers can be misleading. "People have a tendency to remember and blame events just prior to a worsening of MS," Bamford explains. "For example, they'll remember the breakfast before the relapse, but forget all the other breakfasts that had no effect on MS."
In other words, what one person reports as a "cause" of his or her deterioration is likely unrelated to what actually triggered it.
Where Does That Leave Us?
While some causes have been eliminated, others are gaining credibility.
According to the Multiple Sclerosis Association of America, we do have evidence that the risk for developing MS may be associated with:
-- Smoking.
-- Reduced sunlight exposure.
-- Too much saturated fat in the diet.
But it may be a combination of factors that actually sets MS in motion. "People may have different predispositions to developing MS based on genetics or family history," Shin explains, "but a predisposition doesn't mean you'll get MS. There has to be something that triggers this immune system error. What's most likely is that the triggers are different for everyone."
Possibilities currently being investigated include consumption of salt; slow-acting viruses, such as measles or herpes; and whether geography plays a part, since the likelihood of developing MS is much higher in temperate and colder latitudes than in hot, tropical ones.
"Some people are interested in the role of hormones in MS," Shin says. "Women are more affected by MS than men. The age in which women are commonly diagnosed, between 20 to 40, is the time when women are typically most fertile. That hints that estrogen or hormones may play a part in MS."
The Hygiene Hypothesis
Another theory about what causes MS focuses on hygiene. It applies to the developed world, where people frequently wash their hands, use hand sanitizer and sterilize baby bottles.
Shin explains that some scientists theorize human beings have evolved in an environment that is dirty; if we're exposed to parasites, viruses or bacteria at young ages, then perhaps our immune systems adapt to fight those agents. If we're too clean, the theory goes, the immune system may attack other targets and make mistakes.
[See: 5 Rare Diseases You've Never Heard of (Until Now).]
"People have observed that we seem to have an increased incidence of immune-mediated disorders in the developed world. I don't think it's crystal clear that hygiene is behind this for MS. It's worth investigation, but I'd argue that for MS, the causes are multifactorial and the interactions are complex," Shin says.
The Takeaway
Shin points out we've come a long way in understanding MS, especially in the last two decades. "Twenty-five years ago, MS was a completely untreatable disease. We had no idea how to help people. Yet here we are with more than a dozen treatment options that are getting increasingly effective," he says.
The National Multiple Sclerosis Society notes that scientists continue investigating how MS occurs, and how to develop new approaches to repair and protect the nervous system against it. Ultimately, the search for answers may one day help scientists zero in on ways to prevent or cure the disease.
Heidi Godman is a freelance health reporter for U.S. News. Her work has appeared in dozens of online and print publications, including the Harvard Health Letter (where she serves as executive editor), the Chicago Tribune, Baltimore Sun, Orlando Sentinel and Cleveland Clinic Heart Advisor. Heidi also spent more than 20 years as a TV news anchor and health reporter. She's interviewed surgeons in operating rooms, scientists in laboratories and patients in all phases of treatment. Heidi has earned numerous awards for outstanding health reporting and was the first TV broadcaster in the nation to be named a journalism fellow of the American Academy of Neurology. Email Heidi at health@heidigodman.com.
