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Would be helpful if this question pointed to a reference that showed Colorado has the highest rate of multiple sclerosis (MS). Regardless, is there data to support this assertion? Not exactly. Rather Colorado has a higher, not highest, MS prevalence.

  • Decades of observations show global MS prevalence tends to be higher among countries north of the 37o latitude (the 37th parallel) above the equator. Prevalence means proportion of population with the disease.
  • As such, US states above the 37th parallel (below, map on left) also tend to a higher prevalence of MS, as we see from Jason Alcorn’s 2012 US MS prevalence map, using data collected by the US National MS Society (below, map on right).
  • Darker the shade, higher the prevalence of MS.
  • In other words, Minnesota, Vermont and Washington highest.
  • Next, Idaho, Montana and Wyoming.
  • Then, Colorado, Connecticut, Massachusetts, Nebraska, North Dakota, Oregon, Rhode Island.

Questions also asks why.

  • Actual cause(s) of MS is still unidentified.
  • However, epidemiological studies have suggested numerous possible environmental factors.
  • Which of them are causal, not casual?
  • Recently, the most thorough ‘umbrella review’ of meta-analyses of thousands of MS epidemiology studies published through 2014 (Belbasis, Lazaros, et al. “Environmental risk factors and multiple sclerosis: an umbrella review of systematic reviews and meta-analyses.” The Lancet Neurology 14.3 (2015): 263-273) concluded only 3 such factors correlated most compellingly with MS. They are:
    • Circulating IgG antibodies against Epstein-Barr virus nuclear antigen (EBNA).
    • History of infectious mononucleosis.
    • Smoking.

Relationship between latitude (presumably UVB radiation or its effect on efficiency of Vitamin D synthesis) and the above three factors is as yet undeciphered.