In the UKPDS, each 1% decrease in annual mean A1C level reduced the risk of microvascular complications by 37%, peripheral vascular disease (PVD) by 43%, myocardial infarction (MI) by 14%, stroke by 12%, heart failure by 16%, and cataract extraction by 19%.
These data indicate that over time there is a quantifiable relationship between the risk of complications of diabetes and glycemia.
Reference
Stratton IM, Adler, AI, Neil HA, et al. Association of glycemia with macrovascular and microvascular complications of type 2 diabetes (UKPDS 35): prospective observational study. BMJ. 2000; 321:405-412.