Geographic Distribution of Multiple 

 Sclerosis in Relation Geomagnetic 

 Latitude and Cosmic Rays* 



John S. Barlow 



Massachusetts General Hospital, 

 Boston, Massachusetts 



Introduction 



Despite the fact that multiple sclerosis has been known as a clinical 

 entity for over a century, its etiology is still an enigma (Schumacher, 1960). 

 Moreover, there is no specific treatment for the disease, which in its later 

 stages often results in severe crippling. The disability results from interfer- 

 ence with the processes of electrical conduction along nerve fibers in the 

 brain and spinal cord as the myelin sheath of the fibers degenerates in local- 

 ized regions; the term "demyelinating disease" is accordingly used. 



One of the interesting aspects of the disease is its geographic distribution. 

 It has been a clinical impression for some years (Steiner, 1938) that multiple 

 sclerosis does not have a uniform distribution throughout the world, and 

 several epidemiologic surveys have been undertaken to clarify this distribu- 

 tion (McAlpine et al., 1955: Hyllested. 1956: Kurland ct ai, 1957). The 

 disease appears to be appreciably more common in northern than in southern 

 latitudes in North .America and in Europe, but uncommon in the Orient, 

 South America. Africa, and the tropics and subtropics. 



There have been several possible explanations ad\anced for this geo- 

 graphic distribution, some of which I have re\iewed elsewhere (Barlow, 

 1960), but none has appeared to be consistent with all of the a\ailable 

 data for the distribution. More recently, Acheson et al. (1960) have found 

 that the geographic distribution of multiple sclerosis among veterans in the 

 United States correlates strongly in an inverse manner with the average solar 

 radiation of place of birth, and in particular with the December solar radia- 

 tion, the implication being that this agent may in some way act as a preven- 

 tive or protective agent against multiple sclerosis. When the distribution by 

 residence at onset of symptoms was examined, the correlation appeared best 



* This work was supported by the National Institute of Neurological Diseases and 

 BHndnesSj U.S. Public Health Service. 



123 



