Trends in persistent proteinuria in adult-onset diabetes - A population-based study

OBJECTIVE- This study investigates temporal trends in the prevalence and in cidence of persistent proteinuria among people with adult-onset diabetes (a ge greater than or equal to 40 years). RESEARCH DESIGN AND METHODS- The complete community-based medical records o f all Rochester, Minnesota, residents with a diagnosis of diabetes or diabe tes-like condition from 1945 through 1989 were reviewed to determine whethe r they met National Diabetes Data Group (NDDG) criteria. All confirmed diab etes cases residing in Rochester on 1 January 1970 (n = 446), 1980 (n = 647 ), and/or 1990 (n = 940) were identified. The medical records of these prev alence cases were reviewed from the time of the first laboratory urinalysis value to the last visit, death, or 1 April 1992 (whichever came first) for evidence of persistent proteinuria (two consecutive urinalyses positive fo r protein, with no subsequent negative values), Similarly, the medical reco rds of all 1970-1989 diabetes incidence cases (n = 1,252) were reviewed to investigate temporal changes in 1) the likelihood of having persistent prot einuria before the date NDDG criteria was met, i.e., baseline; 2) the risk of persistent proteinuria after baseline; and 3) the relative risk of morta lity associated with persistent proteinuria. RESULTS- The proportion of diabetes prevalence cases with persistent protei nuria on or before the prevalence date declined from 20% in 1970 to 11% in 1980 and 8% in 1990, Among the 1970-1989 diabetes incidence cases, 77 (6%) had persistent proteinuria on or before baseline; the adjusted odds decline d by 50% with each 10-year increase in baseline calendar year (P < 0.001). Among individuals free of persistent proteinuria at baseline, 136 subsequen tly developed persistent proteinuria; the estimated 20-year cumulative inci dence was 41% (95% CI 31-59); the adjusted risk did not differ as a functio n of baseline calendar year. Survival of individuals with persistent protei nuria relative to those without was reduced but did not differ by baseline calendar year. CONCLUSIONS- The prevalence of persistent proteinuria among people with adu lt-onset diabetes in Rochester, Minnesota, declined 60% between 1970 and 19 90. The decline appears because of a decrease in the proportion of diabetes incidence cases with persistent proteinuria before baseline rather than se cular declines in the risk of persistent proteinuria after baseline or secu lar increases in the risk of mortality associated with persistent proteinur ia, Similarity over time in age and fasting glucose at baseline, and at pre valence dates, is evidence that earlier detection of diabetes is not the so le explanation for the decline.