Researchers from the University of Washingto, Seattle, have found that the clinical course of diabetic kidney disease – a strong risk factor for cardiovascular disease among people with diabetes – as described in textbooks and literature has significantly changed.
The study findings, published in the Journal of the American Medical Associatio, show that kidney disease patients are presenting with different clinical features than they have in the past, which could have important implications for research and treatment.
Ian H de Boer, the senior author of the study, suggests that there has been especially a notable shift in the prevalence and chronological manifestation of two main risk indicators of diabetic kidney disease (DKD).
Those are the prevalence of elevated levels of albuminuria in the urine, which is thought to be the first sign of damage in DKD, and a reduced filtration of waste products (or glomerular filtration rate), which is typically a later manifestation of the disease.
According to the results of this study, the prevalence of albuminuria decreased while instances of low estimated estimated glomerular filtration rate (eGFR) has become more prevalent, suggesting a change in presentation of diabetic kidney disease.
De Boer and his colleagues made the discovery after conducting a cross-sectional study including 6251 adults aged 20 years and over who had diabetes and were part of the National Health and Nutrition Examination Survey (NHANES) from 1988 to 2014.
The authors indicated that a small proportion of participants had type 1 diabetes, so the results are primarily relevant to those with type 2 diabetes.
In order to evidence changes in the course of kidney disease progressio, the research scientists tested patients repeatedly for a persistence of albuminuria (here defined as urine albumin/creatinine ratio greater than 30 mg/g), reduced eGFR (greater than 60 mL/min/1.73 m2) or both.
The results first indicated that, over the past 30 years, the prevalence of diabetic kidney disease among the US-based population tested stayed about the same. It was 28.4 per cent in 1988-1994 and 26.2 per cent in 2009-2014.
The researchers have also been able to discern from the data variations in the prevalence ratio of albuminuria and reduced eGFR.
Albuminuria decreased from 20.8 per cent in 1988-1994 to 15.9 per cent in 2009-2014. On the other hand, reduced eGFR increased from 9.2 per cent in 1988-1994 to 14.1 per cent in 2009-2014.
Patients enrolled in the study self reported their age, gender, ethnicity, as well as duration of their diabetes prior to the study. The research team observed that participants with reduced eGFR generally had a long duration of diabetes along with other diabetes complications, like retinopathy and cardiovascular disease.
It is possible that eGFR may be a long-term consequence of diabetes. As for the improvements in albuminuria seen in the study, they occurred only in those aged 65 years or younger and primarily in Caucasians.
De Boer argues that the reduction in the prevalence of albuminuria could be related in part to better diabetes management, increased use of renin-angiotensin-aldosterone system (RAAS) inhibitors, and use of statins.
Overall, these findings make a strong statement that new therapies may be needed to lower the prevalence of reduced eGFR in diabetic kidney disease patients through new research, as current clinical trials commonly target patients with macroalbuminuria who don’t necessarily have concomitant reduced eGFR.