Abstract
INTRODUCTION: Associations of dietary sodium (Na) and potassium (K) with blood pressure (BP) show conflicting results, with limited data in individuals of African ancestry. We examined cross-sectional associations of 24-hour urine Na (UNa(24h)) and K (UK(24h)), proxies for dietary intake, with BP and proteinuria in CKD cohorts in West Africa and USA. METHODS: We analyzed participants in the Diet, CKD and ApolipoproteinL1 (DCA) study, an ancillary of the Human Hereditary and Health in Africa (H3Africa) Kidney Disease Study; and the Chronic Renal Insufficiency Cohort (CRIC) study. The exposures included calibrated UNa(24h), UK(24h) and UNa(24h)-to-UK(24h) ratio. The outcomes were systolic and diastolic BP (SBP and DBP), and 24-hour urine protein at baseline. Using mixed-effect linear regression, we calculated crude and adjusted effect sizes (b coefficients) and 95% confidence intervals. RESULTS: Median UK(24h) excretion was lowest in DCA (36, interquartile range: 28-48) compared with Black (45, interquartile range: 34-57 mmol/24 h) and non-Black CRIC participants, (63, interquartile range: 50-78 mmol/24 h) (all P < 0.001). Median UNa(24h) excretion was lowest in DCA participants. UK(24h) was associated with lower DBP (Q4 vs. Q1, -2.18 [-3.90 to 0.45]) in Black CRIC participants. The association of UK(24h) with DBP was directionally consistent but not significant in the DCA or non-Black CRIC participants. Higher quartiles of UNa(24h) and UNa(24h)/ UK(24h) were associated with higher DBP in non-Black CRIC participants. UNa(24h) was associated with higher proteinuria in all participants. CONCLUSION: The reasons for the differences in associations may arise from Na sensitivity, differences in UK(24h) excretions, and dietary Na-K imbalance. The implications of lower UK(24h) in African populations require future studies.