Measuring and Mapping MS

Multiple sclerosis prevalence

/ Author:  / Reviewed by: Robert Carlson, M.D

Multiple sclerosis (known commonly as MS) is a long-term, chronic disease with symptoms ranging from mild and frustrating to severe and life-altering.

The disease affects the central nervous system, a complicated system that includes the brain, the spinal cord and the optic nerves used for sight.

Symptoms and prognosis for MS vary greatly from patient to patient. The rate of people affected by this disease also varies from location to location around the world.

New research is aiming to better understand both how this disease functions and why its prevalence varies based on geography.

Understanding MS

According to the National Multiple Sclerosis Society (NMSS), though the disease effects the central nervous system, its root is in the immune system. In MS, the immune system attacks the nervous system components, causing the variety of symptoms seen.

As the immune system turns against the central nervous system, the fatty substance protecting nerve fibers (myelin) is damaged, eventually leading to damage of the nerve fibers the myelin is meant to protect.

As this injury occurs in the myelin and nerve fibers, the messages or nerve impulses sent along the spinal cord to and from the brain may be interrupted. This interruption of messages causes the wide range of potential MS symptoms.

According to NMSS, “One person may experience abnormal fatigue and episodes of numbness and tingling. Another could have loss of balance and muscle coordination making walking difficult. Still another could have slurred speech, tremors, stiffness and bladder problems.”

In some cases, symptoms might appear and then disappear, with the patient regaining normal function, and in other cases the disease results in permanent symptoms.

Though the disease can result in paralysis, this does not occur in the majority of cases. NMSS reports that two-thirds of all MS patients do remain able to walk, though some may require the aid of tools like canes.

Furthermore, most people with MS see a normal or near-normal life expectancy, despite the disease diagnosis.

According to the Multiple Sclerosis Trust (MST), a United Kingdom-based charity, for these patients, the treatment of MS focuses on managing individual symptoms through medication, therapies and management strategies.


One aspect of MS that is yet to be completely understood is its seeming prevalence based on location.

MST estimates that 2,500,000 people around the world have MS, though the distribution based on location, gender and ethnicity is not even.

In terms of current rates in the US, NMSS reports that around 400,000 people in the United States have multiple sclerosis and a new diagnosis occurs about every hour.

The disease strikes women more frequently, and there is about three women with MS for every one male patient.

Furthermore, the disease seems to be far more common in certain locations. According to MST, “Generally, the prevalence increases as you travel further north or south from the equator.”

Thus, the regions in America, Africa and Asia that lie around the equator have extremely low MS rates, while Canada and Scotland have very high rates of the disease.

However, even in these locations with high rates, certain ethnic groups appear to have much lower rates than others.

“For instance, the Sami or Lapps of northern Scandinavia and the Inuits in Canada have very low rates of MS. A similar pattern is observed amongst the Maoris of New Zealand,” despite living in regions with a high prevalence of MS, reports MST.

Despite this and despite the higher rates in Caucasians of Northern European descent, NMSS reports that the disease does occur in most ethnic groups, including African Americans, Asians and Hispanics.

The exact reasons for these varying rates are still being explored and yet to be determined conclusively, though there are theories.

Location, Location, Location?

MST reports that since the highest MS rates occur in Northern Europe, North America, Australia and New Zealand, some scientists have theorized that European colonists and settlers carried the disease around the world. This may also explain why some native ethnic groups in these regions have managed to avoid high rates of the disease.

According to The Multiple Sclerosis Resource Centre (MSRC), another MS charity organization based out of the UK, there are several other theories proposed.

Some scientists propose that, based on the higher rates of MS in locations farther away from the equator, sun exposure may play a role in MS.

“The mechanism by which sun exposure would influence MS risk is believed to involve vitamin D – sunlight and UV radiation in particular drives endogenous vitamin D production,” says MSRC (meaning vitamin D produced within the organism).

Questions about age at time of high sun exposure, plus cultural differences like sunscreen use are being explored in research studies related to the development of MS in certain regions.

Other environmental and cultural factors like diet, tolerance to bacteria and cigarette smoking are all being explored as having potential links to the regional differences in MS diagnoses. Time will tell which factor is found to be most relevant, or if a cause yet to be explored is responsible for the geographical differences.

Moving Forward

Regardless of the reasons, with 2.5 million people around the world diagnosed with multiple sclerosis, research about not only why it strikes some more than others, but how to better treat the disease and how to better cope as a patient are sure to continue.

Undergoing medical treatment and practicing self-management of symptoms can help many with MS lead comfortable lives. Furthermore, "In meeting the challenges of living with MS, people often find strength and courage that they did not know they had," says MST.

New research will continue to aim to help support these patients as they cope with life with MS.

Review Date: 
November 8, 2012