Subnormal Kidney Function Mortality Risk Is Stronger With Central Obesity

A large observational study indicates that mild reductions in kidney function are associated with an increased risk of death in middle-aged and older adults, with the elevated risk being particularly pronounced among individuals exhibiting higher levels of central obesity. Published in the International Journal of Obesity, the investigation evaluated how different measures of body fat alter the relationship between subnormal estimated glomerular filtration rate and all-cause mortality over an extended observation period.

The study focused on subnormal kidney function, defined specifically as an estimated glomerular filtration rate between 60 and 90 milliliters per minute per 1.73 square meters. Growing epidemiological evidence indicates that even mild reductions in estimated glomerular filtration rate are linked to adverse kidney outcomes. Researchers sought to examine how excess weight modifies physiological resilience to such early renal declines, given that obesity can disrupt energy balance and metabolic regulation.

To investigate these dynamics, researchers analyzed prospective data from 136,028 participants enrolled in the UK Biobank who presented with baseline subnormal kidney filtration levels. The cohort had a mean age of 59.5 years with a standard deviation of 7.2 years at entry. Over a median follow-up span of 14.7 years, with an interquartile range extending from 13.8 to 15.4 years, researchers documented a total of 12,396 deaths across the study population.

The analytical design utilized fixed-effects Cox proportional hazards regression models to evaluate both linear and nonlinear relationships linking changes in subnormal kidney function to participant survival. To capture complex interactions, investigators implemented tensor product interaction functions to model the joint effects of filtration changes and adiposity, generating two-dimensional exposure–response functions across three primary indicators: waist circumference, body mass index, and waist-to-height ratio.

Within the fully adjusted regression model, every 10-unit decline in estimated glomerular filtration rate was associated with a 9.1 percent increase in excess mortality risk, with a 95 percent confidence interval ranging from 6.6 percent to 11.7 percent. While this baseline association demonstrated a measurable hazard across the entire study sample, the strength and pattern of the association exhibited substantial heterogeneity depending on the specific obesity metric evaluated.

The statistical analyses revealed that central adiposity metrics, represented by waist circumference and waist-to-height ratio, showed markedly stronger modifying effects than general body mass index. Two-dimensional exposure–response surfaces demonstrated a forward shift in mortality risk thresholds among participants with higher central adiposity, indicating that individuals carrying excess abdominal fat experience diminished physiological adaptability when confronting even modest decreases in renal filtration.

The authors concluded that subnormal estimated glomerular filtration rate presents a notable mortality hazard in aging populations that is intensified by central fat accumulation. These findings highlight the potential clinical importance of early detection of subnormal renal decline alongside targeted management of central obesity to sustain metabolic resilience as populations age.

Subject of Research: Association between subnormal estimated glomerular filtration rate, obesity metrics, and mortality

Article Title: Effect of subnormal estimated glomerular filtration rate on mortality varies by obesity metrics: a two-dimensional exposure–response analysis

Article References: Zuo, Q., Wu, J., Li, P., Shang, S., & Zhang, L. (2026). Effect of subnormal estimated glomerular filtration rate on mortality varies by obesity metrics: a two-dimensional exposure–response analysis. International Journal of Obesity. https://doi.org/10.1038/s41366-026-02256-3

Image Credits: AI Generated

DOI: 10.1038/s41366-026-02256-3

Keywords: estimated glomerular filtration rate, subnormal eGFR, central obesity, waist circumference, waist-to-height ratio, body mass index, all-cause mortality, UK Biobank, exposure-response functions, Cox regression, kidney dysfunction, metabolic regulation, tensor product interaction, epidemiology, middle-aged adults, older adults