Background: Rapid kidney decline is associated with mortality and cardiovascular disease, even in the absence of chronic kidney disease. American Indians (AI) have particularly high burden of kidney disease, cardiovascular disease, and stroke. This study aims to examine extreme loss in glomerular function in this population in association with clinical outcomes.
Methods: The Strong Heart Study, a large longitudinal cohort of adult AI participants, collected plasma creatinine at 3 examination visits between 1989-1999. Intraindividual regressions of estimated glomerular filtration rate (eGFR) provided linear estimates of change in kidney function over this time period. Surveillance with physician adjudication identified mortality and cardiovascular events between visit 3 through 2017.
Results: Mean change in eGFR was loss 6.8 mL/min over the ten year baseline (range: -66.0 to +28.9 mL/min). The top 1 percentile lost approximately 5.7 mL/min/year. Participants with extreme eGFR loss were more likely to have diabetes (95% vs 71%), hypertension (49% vs 33%), or longer smoking history, among smokers (19 pack years vs 17 pack years). CKD (eGFR<60 mL/min) was associated only with mortality, independent of slope: HR 1.1 (95% CI 1.0-1.3). However, extreme loss in eGFR (>20 mL/min over baseline period) was associated with mortality, independent of baseline eGFR: HR 3.5 (95% CI 2.7-4.4), and also independently associated with composite CVD events and CHF: HR 1.4 and 1.7 (95% CI 1.1-1.9 and 1.2-2.6), respectively.
Conclusion: This is the first examination of decline in eGFR in association with mortality and CVD among AIs. The implications of these findings are broad: clinical evaluation may benefit from evaluating change in eGFR over time in addition to dichotomous eGFR. Also, these findings suggest there may be aspects of renal function that are not well-marked by clinical CKD, but which may have particular relevance to long-term renal and vascular health.