Recent data found that American Indians were the only group in the United States with a significant decline in age-adjusted diabetic ESKD incidence despite their apparent increasing diabetes prevalence [37
]. Efficacious treatments and practices to reduce risk factors for diabetic ESKD may have contributed to the decline [38
]. Other ethnic groups experienced a slower increase or a plateau in the incidence of diabetic ESKD. Perhaps differences in access to care or physicians’ awareness of increased risk in minority populations may, in part, explain this difference. Similarly, the decline in the age-sex–adjusted incidence of ESKD among diabetic Pima Indians coincided with the introduction and widespread use within this community of new hypoglycemic medicines and medicines that block the renin-angiotensin system (RAS) [39
]. The decline in diabetic ESKD incidence in the Pima Indians occurred primarily in those ≥ 45 years old. The lack of decline in ESKD in younger diabetic Pima Indians may be due to less aggressive management of DN in younger patients or lower death rates from competing causes of death, such as CVD, or both. Conversely, despite improvements in blood pressure, glycemic control, and cholesterol control, the age-sex–adjusted incidence of proteinuria increased from 24.3 cases/1000 person-years in 1967 to 1978 to 38.9 cases/1000 person-years in 1991 to 2002. The incidence of proteinuria remained largely unchanged, however, when those of similar duration of diabetes were compared, indicating that the incidence increased because of an increasing average duration of diabetes in the population [39
]. Thus, newer DN treatments may slow its progression but not its onset.
A substantial proportion of persons with diabetes and microalbuminuria spontaneously regress to normoalbuminuria, implying that microalbuminuria may represent an initial phase of dynamic and reversible kidney injury rather than the onset of an inevitable progression to ESKD. The proportion of diabetic Pima Indians who regressed from microalbuminuria to normoalbuminuria during a median follow-up of 2.4 years was 24%, whereas 19% progressed to macroalbuminuria [40
]. With more advanced kidney disease, fewer persons regressed; most individuals with macroalbuminuria remained in this category (85%) at the second ACR measurement, whereas 15% regressed to microalbuminuria or normoalbuminuria [40
]. Nevertheless, although past measurements predicted progression to ESKD, they did not add to the predictive power when the current measurement was considered. A low current ACR value is associated with good prognosis, regardless of whether earlier values were higher, the same, or lower [40