At present, type 2 diabetics have a 10 years lower life expectancy due to the many often fatal complications they suffer, like stroke, heart attacks, heart failure, end stage renal failure, blindness, limb amputation etc. etc.
We know these complications are mainly related to people not having their diabetes controlled well, most type 2 diabetics have no symptoms, so subjectively will not feel they’re getting any better by having their diabetes controlled, thus treatment adherence very often is low, leading to above named potentially lethal complications. Docs are also partly to blame, since some (many?) of them don’t take type 2 diabetes as seriously as they do type 1 diabetes.
But in theory, if the diabetics involved kept to a healthy lifestyle like NOT SMOKING, keeping their blood pressure at an optimum level, not growing fat, exercising enough, keeping a healthy diet, limiting their alcohol intake (to 1 U/day in females, 2U/day in males), since according to these five low tech lifestyle modifications if started in the forties will raise a female’s life expectancy by 14 years, that of a male by 10.2 years.
