Overview:
There are about 400,000 patients suffering from Multiple Sclerosis in the United Sates Of America today. In the United Kingdom (England) it is estimated that over 120,000 people suffer from the condition. In Australia over 23,000 people, nearly 100,000 in Canada at a rate of nine times the global average for population. Almost 70% of patients manifest symptoms between ages 21 and 40. The disease rarely occurs prior to 10 or after 60 years of age. However, patients as young as 3 and as old as 67 years of age have occurred.
It is estimated that 2.4 million people suffer from multiple sclerosis globally and the number is on the rise.
Geography of MS:
Statistics show there is clearly a link between geography and risk of multiple sclerosis (MS). The further an individual is away from the Earth’s equator the greater the statistical odd’s of onset of the disease. The connection between geographic location and onset of the disease remains elusive. Many researchers show a link between vitamin D and onset of MS. A natural source of vitamin D is sunlight. The further one moves away from the equator the less sunlight is received. Further, there is a very specific geographic distribution of this disease around the world.
A significantly higher incidence of the disease is found in the northernmost latitudes of the northern and the southern hemispheres compared to southernmost latitudes. This observation is based on the incidence of the disease in Scandinavia, northern United States and Canada, as well as Australia and New Zealand.
Studies indicate that immigrants and their descendants tend to take on the risk level — either higher or lower — of the area to which they move. The change in risk, however, may not appear immediately. Those who move in early childhood tend to take on the new risk themselves. For those who move later in life, the change in risk level may not appear until the next generation. While underlining the complex relationship between environmental and genetic factors in determining who develops MS, these studies have also provided support for the opinion that MS is caused by early exposure to some environmental trigger in genetically susceptible individuals.
Data from migration studies (people moving) shows that if the exposure to a higher risk environment occurs during adolescence (before 15 years of age,) the migrant assumes the higher risk of the environment. This concept is nicely illustrated in studies of native-born South African white population with low incidence of the disease versus high incidence of MS among white immigrants from Great Britain, where the disease is much more prevalent.
Epidemics of MS have been reported and these provide further evidence of importance of environmental factors in MS. The most notable “epidemic” was described on the Faroe Islands after they were occupied by British troops in W.W.II. Similar increases in incidence of the disease were seen on Shetland and Orkney Islands, in Iceland, and in Sardinia. A specific “point agent” for these “epidemics” never was identified.
There are also population studies that show difference in susceptibility to MS between different populations. Lapps in Scandinavia appear to be resistant to the disease, contrary to the expectations based on their geographic distribution. Native Americans and Hutterites very infrequently suffer from MS, as opposed to other residents of the North America. MS is uncommon in Japan, China and South America. It is practically unknown among the indigenous people of equatorial Africa and among native Inuit in Alaska. When the racial differences are correlated, White populations are at greater risk than Asian or African populations. Research can not yet explain these obvious inconsistencies in disease distribution, but the knowledge of them may be helpful in assessing specific patient.
MS occurs in most ethnic groups, including African-Americans, Asians and Hispanics/Latinos, but is more common in Caucasians of northern European ancestry.
MS is at least two to three times more common in women than in men, suggesting that hormones may also play a significant role in determining susceptibility to MS. And some recent studies have suggested that the female to male ratio may be as high as three or four to one.
However:
Recent findings are also showing increases in numbers of people with MS in other regions of the world, China, India, South America, Iran and the Middle East for example. It may simply be in the past the disease went unreported or misdiagnosed. Thus now the question becomes exactly how much MS exists in the world. What is known is more people are acquiring multiple sclerosis. This is not a disease on the wane, numbers are rising not falling.
While Vitamin D and distance geographically from the Sun may well be an impacting mechanism towards onset of MS until real tangible numbers can be tallied from all nations globally it is really difficult to say how great an impact geography plays in MS.
Summary:
Current research mindsets clearly display there is linkage between geographic living locations and risk of multiple sclerosis. However the actual causes for this linkage remain unclear. Vitamin D, genetics, environmental factors and other factors may influence risk of onset of the disease.
A recent study in South America by researchers showed more diagnosis of MS seasonally. During seasonal change they have suggested that melatonin levels are altered. Melatonin is a hormone produced by all living animals and that this factor as well may contribute to onset of the disease.
Research continues to try and pin down how geographic location alters the risk factors involved in multiple sclerosis but concrete answers remain elusive.
