Associations Between Change in Kidney Functioning, Age, Race/Ethnicity, and Health Indicators in the Health and Retirement Study

Background: The aging process is accompanied by decline in kidney functioning. It remains unknown to what extent age-related decline in kidney functioning can be attributed to health indicators, and whether rate of decline differs across sociodemographic groups. Methods: Using data from the Health and Retirement Study from 2006/2008 through 2014/2016, we estimated kidney functioning trajectories, determined by cystatin C, among adults aged over 51 over 8 years. We evaluated the role of age, health conditions/behaviors, and genetics in the decline and also examined sociodemographic differentials. Results: Kidney function declined with age and accelerated at older ages, even after adjusting for health conditions/behaviors and genetic differences (eg, 0.019 mg/L annual increase in cystatin C among 70-79 compared to 0.007 mg/L among 52-59 at baseline). Decline occurred faster among those with uncontrolled diabetes (0.008, p =.009), heart conditions (0.007, p <.000), and obesity (0.005, p =.033).Hispanic participants (0.007, p =.039) declined faster than non-Hispanic White persons due to diabetes, heart conditions, and obesity; non-Hispanic Black participants had worse baseline kidney functioning (0.099, p <.000), but only one fourth of this Black-White difference was explained by investigated risk factors. People with higher education experienced slower decline (-0.009, p =.004). Conclusions: Age was a significant predictor of decline in kidney functioning, and its association was not fully explained by health conditions/ behaviors, or genetics. Better management of diabetes, heart conditions, and obesity is effective in slowing this decline. Baseline differences in kidney functioning (eg, between non-Hispanic White and Black persons; those with and without hypertension) suggest disparities occur early in the life course and require early interventions.