Looking at the Chinese as a population has been very useful when studying chronic diseases.

According to Multiple Sclerosis International, the prevalence of MS in China is between one and 50 for every 100,000 people. The situation, however, changes when looking at immigrants who have come to Canada from countries where the exposure to the sun is different.

Canadians of Chinese origin were 10 times more likely to have MS than people in China, Savoie said. "Some of them have more severe MS than Canadian counterparts of Caucasian origin and that may tell us something about the fact that when you move across the globe, you're reacting, in fact, to these changes in the environment, including changes in exposure to vitamin D."

http://news.xinhuanet.com/english2010/health/2011-08/26/c_131077336.htm 

Vitamin D is obviously a very important component in this discussion, as most of Canada is at a northern latitude compared to China.  But the Chinese are also have problems with vitamin D deficiencies in their own country--

Subclinical vitamin D deficiency was widespread among Beijing adolescent girls in winter. Low plasma 25-hydroxyvitamin D concentrations in summer, low calcium intake, and low plasma calcium concentrations in winter were the main risk factors for vitamin D deficiency in winter.

http://www.ajcn.org/content/74/4/494.short

What else changes for Chinese people who move to Canada?  What other factors are new to them?

The western diet.  

This has been studied in relationship to the endothelium and heart disease by Dr. T. Colin Campbell.

Six years ago a small Texas publisher released an obscure book written by a father-son research team. The work, based on a series of studies conducted in rural China and Taiwan, challenged the conventional wisdom about health and nutrition by espousing the benefits of a plant-based diet.

T. Colin Campbell, Ph.D.

To everyone’s surprise, the book, called “The China Study,” has since sold 500,000 copies, making it one of the country’s best-selling nutrition titles. The book focuses on the knowledge gained from the China Study, a 20-year partnership of Cornell University, Oxford University and the Chinese Academy of Preventive Medicine that showed high consumption of animal-based foods is associated with more chronic disease, while those who ate primarily a plant-based diet were the healthiest.

http://well.blogs.nytimes.com/2011/01/07/nutrition-advice-from-the-china-study/

MS researchers need to look beyond vitamin D and latitude as the only environmental factor creating growing numbers of MS patients.  We need to study the vasculature and the affects of the western diet.  I do not write this to start debates or arguments on one diet over another....I write this because I've seen the relationship of endothelial dysfunction and diet in my husband's health, a Californian man who has spent his entire life in sunshine, and has the vitamin D levels and basal cells to show for it!   I hope to encourage others to look into the connection....however that manifests in your own situation.  

be well,

Joan