Changing incidence of glomerular disease in Olmsted County, Minnesota: a 30-year renal biopsy study

Area of Science:

• Nephrology
• Epidemiology
• Internal Medicine

Background:

• Membranous nephropathy (MN) was historically the most common cause of nephrotic syndrome in white adults.
• Recent studies suggested an increasing incidence of focal segmental glomerulosclerosis (FSGS), but data often came from specialized centers.
• The general population's incidence trends for glomerular diseases (GN) required validation.

Purpose of the Study:

• To investigate the population-based incidence trends of various forms of glomerular disease (GN) in Olmsted County, MN.
• To validate and clarify the rising incidence of FSGS and other GN subtypes in a general population.
• To determine the current leading causes of nephrotic syndrome in white adults.

Main Methods:

• Retrospective review of kidney biopsy data from Olmsted County residents diagnosed with non-diabetic glomerular disease between 1974 and 2003.
• Categorization of biopsies into specific GN types: FSGS, MN, minimal change, lupus nephritis, MPGN, IgAN, crescentic/necrotizing GN, and other.
• Calculation of age- and gender-adjusted annual incidence rates per 100,000 population, comparing early (1974-1983) and late (1994-2003) periods.

Main Results:

• Overall GN incidence more than doubled between the two periods (P < 0.001).
• FSGS incidence increased 13-fold (P < 0.001), and IgA nephropathy (IgAN) incidence increased threefold (P = 0.002).
• From 1994-2003, IgAN was most frequent (25%), followed by FSGS (20%) and MN (11%), with FSGS being the leading cause of nephrotic syndrome.

Conclusions:

• The incidence of glomerular disease is increasing in the general population.
• Focal segmental glomerulosclerosis (FSGS) shows a dramatic rise in incidence and is now the leading cause of nephrotic syndrome in white adults.
• Population-based studies are crucial for accurately assessing trends in kidney diseases like FSGS and IgAN.