#960 Trends in eGFR and ultra-processed food intake in relationship to income among United States adults

Abstract

Abstract Background and Aims Ultra-processed foods (UPF) are formulations of ingredients that are mostly of exclusive industrial use and may contain additives like artificial colors, flavors, or stabilizers. The sale and consumption of these foods has been increasing despite their associations with increased risk for several non-communicable diseases including chronic kidney disease. Ultra-processed foods are widely accessible, more shelf-stable and convenient while tending to be more affordable and lower in nutritional quality. The aim of this study was to evaluate trends in kidney function and UPF intake and temporal effect of income among United States (US) adults. Method We used dietary intake data collected with 24-hour dietary recalls from 35160 US adults across 8 cycles of the National Health and Nutrition Examination Survey (NHANES) (from 2003-2004 to 2017-2018 cycles) to categorize intake using the Nova processed food classification system. Poisson regression models were used to assess the 15-year trends in populations at risk for kidney function decline (measured by estimated glomerular filtration rate [eGFR]) and higher percentage of calories from UPF (PC-UPF) consumed along with the temporal effect of income in select subpopulations and adjusted for age and gender and non-linear effects of income and age). Results Over the past 15 years eGFR, PC-UPF, and self-reported income continue to increase among US adults. However, the associations between eGFR, PC-UPF and income are quite complex, vary by subpopulation and non-linearly depend on age. Specifically, among Black adults adjusted for age (age2) and gender, eGFR was the lowest (85 mL/min/1.73 m2, 95% CI: 84.9, 85.0 mL/min/1.73 m2) among those with the lowest ($2,500) and highest ($125,000) income (p = 0.0000000579 for a quadratic term of income), respectively. Hispanic and Mexican Americans also have similar pattern eGFR with the lowest and highest income though the eGFR is consistently higher than White and Black Americans. Across cycles, White Americans with the lowest income ($2,500) have the highest PC-UPF (range: 57-62%, p <2e-16; mean: 59.4%, 95% CI: 59.3, 59.6%) while Black Americans with the lowest ($2,500) and highest income ($125,000) have the highest PC-UPF (range: 53-58%, p <2e-16; mean: 54.8%, 95% CI: 54.3, 55.4%). Income levels does not predict PC-UPF among Mexican Americans. Overall, the PC-UPF is steadily increasing in all population subgroups. Conclusion Among Non-White US adults, higher eGFR was associated with higher income until reaching a group-specific threshold when the relationship reversed. We observed a similar threshold pattern in the association between PC-UPF and income among Black and Hispanic Americans. These complex non-linear relationships between eGFR, PC-UPF and income are driven in part by age-related association and warrant further exploration.