The relationship between exposure to glycemia over time and incidence of microvascular and macrovascular complications was evaluated in a prospective observational study of 4,585 patients with type 2 diabetes. These patients had been recruited for the UKPDS clinical trial and had A1c measured 3 months after the diagnosis of diabetes. Glycemia exposure over time for each individual was determined from the updated mean of annual A1c measurements made each year during follow-up. Subjects were grouped according to their updated mean A1c concentrations into the following categories: <6%; 6% to <7%; 7% to <8%; 8% to <9%; 9% to <10%; and >=10%.
After adjusting for age, sex, ethnicity, and duration of diabetes, the incidence of microvascular and macrovascular complications increased with each higher category of updated A1c. This slide shows the adjusted incidence of any diabetes-related endpoint relative to the updated mean A1c for white men aged 50 to 54 years at diagnosis with a mean duration of diabetes of 10 years. Diabetes-related complications increased threefold over the range of A1c from <6% to >=10%. Notably, there was no evidence of a threshold for A1c with respect to incidence of diabetes-related complications.

Stratton IM, et al. BMJ. 2000;321:405-412.