Multiple sclerosis is a strange and destructive disease. It is an autoimmune and also a neurological disease, a condition where the body’s immune system attacks the central nervous system. This vital system includes the brain, spinal cord and nerve network — and although the largest components are in the center of the body, ultimately the central nervous system controls almost everything. And when a patient’s complex control center is disrupted, everything can change.

Dr. Tamara Miller, medical director and CEO of Advanced Neurology of Colorado, MS Center of the Rockies and Advanced Neurosciences Research, has been studying the disease and treating patients for over two decades. As principal investigator in over 70 clinical MS trials, she’s a well-known expert in the field. In an interview, she discussed the complex condition and what it’s like for patients who have MS.

The Symptom Set Varies

The body’s main defense mechanism, the immune system, may attack any part of the central nervous system. When this happens, a patient experiences a MS exacerbation, or relapse. Miller said she can often determine the location of inflammation in patients with relapses based on their symptoms.

“I had a patient come in with double vision, dizziness and speech problems,” she said. “I know his inflammation is in the brain stem. If he had an MRI, that’s where the lesion would be.”

This doesn’t work for every symptom, and sometimes patients have inflammatory lesions show up on an MRI, but they don’t have physical symptoms. “We call that invisible disease activity,” Miller said.

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The Vitamin D Connection

Low levels of vitamin D are both a risk factor for developing the disease and a complication for MS patients, Miller explained.

“I check patients with MS, and without MS, for vitamin D, in fact, I even tested my kids,” she added.

“Vitamin D is a type of hormone, and it’s a powerful player in immune function,” said Miller. But the connection isn’t quite that simple. “The strongest genetic factor for MS is a specific gene, HLA DRB1*1501, and its activity appears to be influenced by vitamin D. So people with this gene and low vitamin D levels seem to have more of a risk for MS.”

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The Latitude Factor

There is a significant geographic component to MS, but it usually comes into play long before any symptoms occur.

“The farther away from the equator, your chances of getting MS increases,” said Miller.

This risk factor is in play until age 15, so Miller asks all new patients where they grew up. After that, latitude doesn’t seem to make a difference in a MS diagnosis or a patient’s symptoms, aside from heat-related ones.

“So something happens as [patients are] growing, developing. That’s why we think there’s an environmental agent, a genetic agent and an infectious agent,” she said.

The exact cause is unknown and these are all theories, Miller emphasized, but evidence strongly points toward the interplay of all three risk factors.

The Demographics of the Disease

MS is two to three times more common in women than in men, and it’s also diagnosed more often in people of Caucasian and Northern European descent. About 2 million people worldwide have MS, with a disproportionate number — about 1 in 5 or 400,000 — of them living in the U.S. People are generally diagnosed between the ages of 20 and 45, making it the most common neurological disease in younger adults.

Miller advises her MS patients to eat a healthy diet and to stay active because that seems to keep symptoms in check for many people. Plus, healthful habits can help people avoid obesity, “which is a problem for any disease,” she said.

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Women with MS find that pregnancy and breast-feeding can dramatically reduce relapses, and many find it may also reduce symptoms.

“We know there’s a protective effect. We don’t know why that is, it could be hormonal,” said Miller, adding that research is being conducted on a possible link.

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“There’s a lot of [MS] research going on,” Miller noted, and there’s “a lot of hope right now.”

Lacie Glover writes for NerdWallet Health, a website that helps people reduce their medical bills.