18% of oral contraceptive users developed macroalbuminuria compared with 2% of nonusers.
The use of oral contraceptives and accompanying activation of the renin angiotensin system (RAS) appears to be a risk factor for diabetic nephropathy. Dr. Sofia B. Ahmed of Brigham and Women’s Hospital, Boston and colleagues note that the strong association between RAS and diabetic nephropathy led them to investigate a possible connection with oral contraceptive use.
The researchers initially studied 12 diabetic oral contraceptive users and 10 nondiabetic oral contraceptive users. Dr. Ahmed’s team also included 29 diabetic and 41 nondiabetic subjects who did not use oral contraceptives. Renal plasma flow in response to captopril was used as an index of RAS activity.
The nondiabetic nonusers showed a "minimal" increase compared to a significantly greater increase in nondiabetic oral contraceptive users. Diabetic nonusers also had a significantly greater and anticipated increase, but the vasodilator response was greatest in the diabetic oral contraceptive users.
The renal plasma flow responses to captopril, and to ACE inhibitors in a subset of subjects, "were highly correlated," suggesting, say the researchers, "clear involvement of the RAS."
The researchers then went on to gauge the impact of oral contraceptive use in a cohort of 114 women with newly diagnosed type I diabetes.
After a median of 20.7 years of follow-up, 18% of oral contraceptive users developed macroalbuminuria compared with 2% of nonusers. After adjustment for age at onset and blood pressure, oral contraceptive use remained a significant predictor of development of the condition (relative risk, 8.9).
Diabetes Care 2005;28:1988-1994.