From study[1]: "Our dataset includes 1 749 400 individuals with records at New York-Presbyterian/Columbia University Medical Center born between 1900 and 2000 i

From study[1]: "Our dataset includes 1 749 400 individuals with records at New York-Presbyterian/Columbia University Medical Center born between 1900 and 2000 inclusive." They also compare some of their data to data from Denmark. So it's all Northern hemisphere, mid-latitudes. [1] http://jamia.oxfordjournals.org/content/jaminfo/early/2015/06/01/jamia.ocv046.full.pdf http://jamia.oxfordjournals.org/content/jaminfo/early/2015/0...