The incidence of multiple sclerosis is TRIPLE in the PNW. Is sunlight the problem?

Brooke Carmen

Author: Brooke Carmen, PT, DPT: Doctor of Physical Therapy and Blog Contributor.  Loves fun informational gems.  Fitness addict and wannabe foodie. Emphasizes patient-specific treatment style and promotes goal-oriented care. Learn more about Brooke on here.

Did you know that the prevalence of MULTIPLE SCLEROSIS (MS) is higher in the Pacific Northwest than other parts of the country?  MS is linked to a deficiency of VITAMIN D. Vitamin D is linked to sunlight. Is it a coincidence that MS is higher in our region which is known to have less sunlight?

Vitamin D

MS is a disease in which the conduction of your nerves are disrupted from a degeneration-like presentation of the sheaths around them. Effects of MS can vary, but it can present as muscle weakness, vision disruptions, psychiatric problems, sensation deficits, and coordination difficulty. MS is an AUTOIMMUNE DISEASE (when your good cells attack your own good cells) with no known cause. The cause is thought to be from both ENVIRONMENTAL and GENETIC FACTORS.

Rainy Day

One proposed theory of an environmental factor is a deficit of vitamin D which is linked to sunlight. This theory is one on the top of the lists of researchers looking into MS. Why is it that MS up to three times higher in the PNW? As some billboards have said, “Is it the trees? Is it the rain?” Unfortunately, the answer is we don’t know.

Dr. Jim Bowen, an MS specialist in the NW who works in the Swedish Medical Center in Seattle notes that there is a higher prevalence of MS in the NW. In fact, our state just directly below us, California, has a lower prevalence of MS. Dr. Jim Bowen can’t give a solid answer to why, but he does state that “It’s more common in certain ethnic groups, especially those from northern European backgrounds.” There are many Scandinavian immigrants in the PNW which could be the answer, rather than the lack of sunlight. [1]

What we do know about MS is that it is seen in high clusters on the 49th parallel. [1] The further away from the equator, the more common. Dr. Bowen has looked into environmental factors, such as soil, rainfall, and pollution contributions, yet none have been directly linked to MS thus far, sunlight included. [1]

Scientists haven’t found out how to prevent MS, however, there is some speculation about reducing your risk. That’s where Vitamin D comes into play. We know that you can get Vitamin D from sun, fatty fish, milks, supplements, and some cereal products. [2] So, having a healthy intake of Vitamin D as well as all of your other vitamins is a good idea. Interestingly, some studies have found that coffee and red wine intake decrease your MS likelihood. [2] I would have to research this more before betting my life on it.

Things that do increase your likelihood of MS?  Smoking and a first-degree relative with MS (parent, sibling, child). Those are facts. Another argument against smoking.

I didn’t write this to scare you about living in the PNW. I wrote it to increase your awareness of a disease prevalent in our region. The answer is, we don’t know why MS is more prevalent here. The good news is, it’s not sunlight alone. Maybe if you are a smoker with an European background living in the PNW, you carry the genetic mutation for MS. If you don’t have a history of MS in your family, you are likely not in the high running for developing it.

If you have any questions regarding the topics in this blog, I would love to chat with you directly. You can email me at Please see the list below for definitions of capitalized terms above.


MULTIPLE SCLEROSIS (MS): “an unpredictable, often disabling disease of the central nervous system that disrupts the flow of information within the brain and between the brain and body” [3]

VITAMIN D:  refers to a group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, iron, magnesium, phosphate, and zinc. In humans, the most important compounds in this group are vitamin D₃ and vitamin D₂ [4]

AUTOIMMUNE DISORDER: a disease in which the body produces antibodies to attack its own tissue

ENVIRONMENTAL FACTOR:  also known as “ecological factor.” Any factor that influences a living organism. Examples include pH, sunlight, pollution, and soil.

GENETIC FACTOR:  referring to genetics, genes, or inheritance.


[1] By Knkx on Fri, 12/16/2011 - 09:56. "Is It Really True That There Is More MS in the Northwest?" I Wonder Why ... ? from KPLU. N.p., 16 Dec. 2011. Web. 06 Oct. 2016.

[2] "Can You Prevent Multiple Sclerosis?" N.p., 12 Aug. 2016. Web. 06 Oct. 2016.

[3] "What Is MS?" National Multiple Sclerosis Society. N.p., n.d. Web. 06 Oct. 2016.

[4] "Vitamin D." Wikipedia. Wikimedia Foundation, n.d. Web. 06 Oct. 2016.