It could be a "racial" trait. Australian Aboriginals and those of Torres Strait descent are high on the list. having diabetes makes sufferers susceptible to immune dysregulation with opens people to infection generally. It is only rational to screen those with diabetes for tuberculosis. This is not currently done.
It is not known if dysregulation is the cause of problem. Historical data is not much help because diabetes was not an identifiable disease while TB was, in past centuries. Research is being done to find find the reason for it. Reduce the prevalence of diabetes and cases of TB fall. It is as simple as that.
◆ Science by Ty Buchanan ◆