In areas near the equator, MS occurs in fewer than 1 out of 100,000 people. In areas
farther from the equator—such as northern Europe and northern North America—MS
occurs in around 30 to 80 out of 100,000 people.1 When moving south of the equator, the number of people
with MS is less dramatic, but the same trend is seen.
There are four types:
Relapsing-remitting. This is the most common form. You have flare-ups followed by periods without symptoms, called recovery.
Primary-progressive. With this type, you do not get the ups and downs. Your symptoms get worse over time.
Secondary-progressive. You get flares and recovery periods at the start, then symptoms steadily worsen.
Progressive-relapsing. This form is very rare. Symptoms worsen from the start. You experience...
Some evidence suggests that people who move from a high-risk to a
low-risk area before the age of 15 reduce their chances of developing MS.
But the same is true in reverse. In those who move from a low-risk area to
a high-risk area before the age of 15, the risk of getting MS increases. Those
older than 15 when they move to a new area retain the risk associated with
their old area.1
Most experts agree that this unusual relationship between geographic
location and MS suggests that an environmental factor is partly responsible for
causing the disease.