EPIDEMIOLOGY OF PRIMARY GLOMERULAR-DISEASES IN A FRENCH REGION - VARIATIONS ACCORDING TO PERIOD AND AGE

Between January 1, 1976 and December 31, 1990, histological diagnosis of primary glomerular diseases (PGD) was made in 480 patients born and living at the time of diagnosis in a region of France, comprising 410,664 inhabitants, of whom 390,574 were aged from 10 to 80 years. The prevalence of PGD during a 70 year exposure to risk (10 to 80 years of age) was evaluated to 5.7 in 1000 (7.6 in 1000 males and 3.8 in 1000 females). The most common PGD was IgA nephropathy with a prevalence of 1.9 in 1000 (3.3 in 1000 males, 1 in 1000 females). The annual incidence of the disease was evaluated separately for three consecutive five-year periods: period A (1976-80), period B (1981-85), and period C (1986-90). Within each of these three periods the number of patients with PGD was 179, 170 and 131, respectively, and annual incidence was 9.3, 8.8 and 6.7 in 100,000. The incidence of IgA nephropathy remained the same throughout the three periods: 2.6, 3.1 and 2.5 in 100,000. The incidence of membranoproliferative glomerulonephritis decreased from 1981 onward (0.9, 0.5 and 0.15 in 100,000), while that of membranous nephropathy increased slightly (1.2, 1.6 and 1.7 in 100,000). Acute streptococcal glomerulonephritis virtually disappeared during periods B and C. Lipoid nephrosis was less frequent in period C and idiopathic proliferative glomerulonephritis with crescents slightly increased (0.3, 0.4 and 0.6 in 100,000). There was no significant difference between the three periods regarding the incidence of other PGD. The incidence of IgA nephropathy was three- to fourfold higher in the adult aged from 20 to 59 years than in the elderly. In contrast, membranous nephropathy was threefold more frequent in the elderly than in the adult. Therefore, only some histopathological forms have a different incidence according to age, but the major information furnished by this study is that the risk of occurrence of a PGD is similar in the population living in the area, whatever the age group (10 to 19 years, 6.4 in 100,000 inhabitants; 20 to 39, 7.1 in 100,000; 40 to 59, 8.4 in 100,000; 60 to 79, 8.4 in 100,000). We also confirm that the most common PGD going to end-stage renal disease is IgA nephropathy, particularly under 60 years of age (0.8 in 100,000). In contrast, membranous nephropathy is a less frequent cause of ESRD (0.2 in 100,000).