UNCHANGED INCIDENCE OF DIABETIC NEPHROPATHY IN IDDM PATIENTS

Recently, a dramatic decline in the cumulative incidence of diabetic n ephropathy (10% after 25 years of diabetes) has been reported in insul in-dependent diabetes mellitus (IDDM) patients diagnosed before the ag e of 15 years be between 1961 and 1980. In a clinic-based study, we as sessed recent trends; in the incidence of diabetic nephropathy. All 35 6 patients in whom IDDM-was diagnosed before the age of 41 years betwe en 1965 and 1979, identified in 1984, were followed until 1991 or unti l death. All patients were Caucasians and resided in Copenhagen. The c umulative incidences (life-table method) of diabetic nephropathy (urin ary albumin excretion greater than or equal to 300 mg/24 h in two out of three consecutive samples) after 15 years of diabetes and in 1991 w ere 18 +/- 4 and 35 +/- 5% (cumulative incidence +/- SE; onset of diab etes 1965-1969, n = 113), 20 +/- 4 and 35 +/- 5% (onset of diabetes 19 70-1974, n = 130), and 16 +/- 5% (onset of diabetes 1975-1979, n : 113 ), respectively (NS at 15 years). The prevalence of persistent microal buminuria (31-299 mg/24 h) at time of follow-up was 24% (95% confidenc e interval: 16-33) in the group with onset of diabetes in 1966-1969, 2 8%, (20-36) with onset of diabetes in 1970-1974, and 19% (13-28) with onset of diabetes in 1975-1979 (NS). The mean +/- SE HbA(1c) measured yearly beginning in 1984 was higher in patients with nephropathy (9.4 +/- 0.1%) and persistent microalbuminuria (8.9 +/- 0.1%) than in patie nts with normoalbuminuria (8.5 +/- 0.1%; P < 0.001). Our study reveale d no evidence suggesting a so-called calendar effect, i.e., declining cumulative incidence of diabetic nephropathy with increasing calendar year of diabetes onset. The lack of calendar effect may in part be exp lained by poor metabolic control and a high and unchanged prevalence o f smoking (58-71%).