Background and objectives: Low socioeconomic status confers unfavorable health, but the degree and mechanisms by which life course socioeconomic status affects kidney health is unclear.
Design, setting, participants, & measurements: We examined the association between cumulative lifetime socioeconomic status and CKD in black Americans in the Jackson Heart Study. We used conditional process analysis to evaluate allostatic load as a potential mediator of this relation. Cumulative lifetime socioeconomic status was an age-standardized z-score, which has 1-SD units by definition, and derived from self-reported childhood socioeconomic status, education, and income at baseline. Allostatic load encompassed 11 baseline biomarkers subsuming neuroendocrine, metabolic, autonomic, and immune physiologic systems. CKD outcomes included prevalent CKD at baseline and eGFR decline and incident CKD over follow-up.
Results: Among 3421 participants at baseline (mean age 55 years [SD 13]; 63% female), cumulative lifetime socioeconomic status ranged from -3.3 to 2.3, and 673 (20%) had prevalent CKD. After multivariable adjustment, lower cumulative lifetime socioeconomic status was associated with greater prevalence of CKD both directly (odds ratio [OR], 1.18; 95% confidence interval [95% CI], 1.04 to 1.33 per 1 SD and OR, 1.45; 95% CI, 1.15 to 1.83 in lowest versus highest tertile) and via higher allostatic load (OR, 1.09; 95% CI, 1.06 to 1.12 per 1 SD and OR, 1.17; 95% CI, 1.11 to 1.24 in lowest versus highest tertile). After a median follow-up of 8 years (interquartile range, 7-8 years), mean annual eGFR decline was 1 ml/min per 1.73 m2 (SD 2), and 254 out of 2043 (12%) participants developed incident CKD. Lower cumulative lifetime socioeconomic status was only indirectly associated with greater CKD incidence (OR, 1.04; 95% CI, 1.01 to 1.07 per 1 SD and OR, 1.08; 95% CI, 1.02 to 1.14 in lowest versus highest tertile) and modestly faster annual eGFR decline, in milliliters per minute (OR, 0.01; 95% CI, 0.00 to 0.02 per 1 SD and OR, 0.02; 95% CI, 0.00 to 0.04 in lowest versus highest tertile), via higher baseline allostatic load.
Conclusions: Lower cumulative lifetime socioeconomic status was substantially associated with CKD prevalence but modestly with CKD incidence and eGFR decline via baseline allostatic load.
Keywords: African-Americans; United States; allostasis; allostatic load; biomarkers; child; chronic renal insufficiency; female; follow-up studies; glomerular filtration rate; humans; incidence; income; kidney; kidney disease; kidney diseases; life course; longitudinal studies; prevalence; self report; social class; socioeconomic status.
Copyright © 2020 by the American Society of Nephrology.