Demographic characteristics of Canadian and US study participants in comparison to their respective national population characteristics.

12011 population data for individuals 18 years and older in Canada was obtained from Statistics Canada [44].
22010 population data for individuals 18 years and older in the US was obtained from the US Census Bureau [46].
3Regions were:
Midwest (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin);
Northeast (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont);
South (Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, West Virginia);
West (Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming).
42006 education data for individuals 20 years and over in Canada (most current and available data) [43].
52010 education data for individuals 18 years and over in the US [45].
*Significant at p<0.01.
+An additional Fisher’s exact test was conducted to take into account of the small sample size in some Provinces and Territories; the results remain unchanged with no statistically significant relationship between the study population and the national population distributions (p = 1.000).
∧MD – Doctor of Medicine degree, DVM – Doctor of Veterinary Medicine degree.