Population-based survey and analysis of trends in the prevalence of diabetic nephropathy in Type 1 diabetes

Aims To determine the prevalence of the various stages of diabetic nephropathy in Type 1 diabetes in a population-based survey. To make direct comparison with results from previous published studies to assess current trends. Methods Identification of all Type 1 patients using a population-based diabetes register. Urine samples for albumin assay were obtained at clinic visit and by postal request. Prevalence rates were calculated specifically for direct comparisons with previously published surveys. Results This study and European data from the 1990s show a clear reduction in the cumulative prevalence of microalbuminuria and established nephropathy compared with surveys from Copenhagen (1985), Pittsburgh (1986-8) and Boston (1992). In North Wales in 1999 the overall cumulative prevalence of microalbuminuria was 27.2% (95% confidence interval (CI) 24.3-30.1%) and established nephropathy was 9.6% (7.7-11.5%). Comparisons with data from EURODIAB and from Spain indicated similar results, although the prevalence of microalbuminuria was lower in North Wales than in the EURODIAB study. Significantly lower rates of nephropathy were seen in more recent Swedish cohorts. Diabetic nephropathy remains more common in males. Microalbuminuria before 10 years duration of diabetes was seen at all post-pubertal ages. Conclusions Rates of nephropathy in Europe in the 1990s are lower than a decade ago. Modern methods of management are therefore associated with demonstrable benefit at the population level. The lowest rates of nephropathy are associated with optimum glycaemic control in Swedish data, indicating the importance of metabolic in addition to haemodynamic factors.