Diabetic Nephropathy: Incidence, Prevalence, and Treatment

Diabetic nephropathy represents a significant risk for morbidity and mortality within all patient populations with diabetes (1,2). Major efforts have been mounted to address the increasing incidence of both type I and type II diabetes and for all diabetic patients the incidence of microand/or macrovascular complications. Despite the progress in demonstrating a clear benefit of optimal glycemic control in affecting the complications of diabetes as denned by papers emanating from the Diabetes Control and Complications Trial (DCCT) Study Group (3,4), a substantial number of patients still experience diabetic renal disease, extending from the presentation of microalbuminuria to significant clinical diabetic nephropathy and finally to end-stage renal failure. The large number of diabetic patients undergoing dialysis and/or transplantation attests to the inability to apply intensive diabetic therapy to many patients. The beneficial application of antihypertensive agents to retard or arrest the progression of diabetic nephropathy (5,6) arises from a primary failure to prevent diabetes and a secondary inability of routine diabetic therapy to alter the course of diabetic nephropathy. Within the last decade several papers from epidemiological and/or populationbased studies have determined the incidence and prevalence of diabetic nephropathy, as documented by various measurements and at different stages of disease (1,7-11). One of the most recent studies from a national perspective calculated the incidence and prevalence of Finnish hospital admissions for diabetic nephropathy over 2-3 decades (11). This study, like some of the others, advantageously used one of the rich databases within the national health systems in Scandinavia, each capable of tracking the health care of each individual within the population. Without attempting to address the possible inconsistencies within the Finnish system of classification of diseases summarized in a thoughtful manner by the authors, I wish to contrast current data with those previously reported from Denmark (8,10), also reflecting a recent unchanged incidence in diabetic nephropathy, and uniquely from Sweden, wherein a decline in the incidence of this major complication was reported (9). The currently reported data from hospital admissions in Finland resemble those reported from Denmark by Rossing et al. (10) on the unchanged incidence of diabetic nephropathy in a very large and highly effective regional referral clinic. The contrast lies with the study by Boestig et al. (9) in a very carefully monitored and implemented system of delivering health care to a largely pediatric population in the Linkoping area of Sweden. The discussion sections of both the Danish and Finish studies are highly informative about why differences may exist between their experiences and the Linkoping diabetic population. The bottom line lies with the level of glycemic control achieved in Linkoping, contrasted with the Danish (10), Finnish (11), and even other Swedish populations (12). The results of the Stockholm Diabetes Intervention Study provide great insight into this issue (12). Their achievement of a difference in mean HbAlc in their intensive versus standard treatment groups nearly matches that of the DCCT (Table 1) (1). From my own perspective within the DCCT Study Group, the capacity to achieve such consistently low HbAlc levels over an extended period of time is a significant accomplishment. Thus, the "routine" management of patients reported by Boestig et al. (9) in Linkoping equaled the "intensive" HbAlc values at other sites (Table 1). In turn, these results would expectedly lower the incidence and prevalence of diabetic complications, as demonstrated by the North American (3) and Swedish (12) trials. What is the impact of these several messages for the physician trying his or her best to deliver the best possible care to all diabetic patients and thereby to diminish the possibility of complications against an increasing risk of hypoglycemia (1,13)? Under nearly all circumstances in the routine practice of diabetic medicine, the delivery of DCCT or Stockholm Study intensive management presents the major practical challenge of implementation. Most health care delivery teams cannot do so, even in Scandinavia as shown by the recent Danish (10) and Finnish (11) studies and earlier from the group in Linkoping (14) wherein HbA: levels averaged 10% (HbAlc, —8%). The bad news potentially relates to the "disparity" in the most recent Linkoping experience with the rest of Scandinavia and therefore much of the world. Taken to a logical conclusion, the incidence of diabetic nephropathy is not declining. The total health care burden of diabetic complications is increasing substantially with the increase in the combined incidence in the various types of diabetes. However, the good news lies with the emphasis on the well-described benefits of intensive diabetic management in lowering the incidence of albuminuria and the delivery of better diabetic management to all patients. We know where we need to travel, but we do not know which vehicles will practically transport us to our goals. Hopefully, those institutions that have achieved "intensive" results in routine practice will share their findings and protocols most assiduously with others in the peer-reviewed literature.