Associations between multimorbidity and kidney function decline in old age: A population-based cohort study.

Background: Individual chronic conditions have been linked to kidney function decline; however, the role of multimorbidity (the presence of ≥2 conditions) and multimorbidity patterns remains unclear.

Methods: A total of 3094 individuals from the Swedish National study on Aging and Care in Kungsholmen (SNAC-K) were followed for 15 years. Multimorbidity was operationalized as the number of chronic conditions and multimorbidity patterns identified using latent class analysis (LCA). Joint models and Cox regression models were used to explore the associations between multimorbidity, and subsequent absolute and relative (≥25% decline from baseline) changes, respectively, in the estimated glomerular filtration rate (eGFR) calculated using the creatinine-based Berlin Initiative Study equation.

Results: Mean age of the sample was 73.9, and 87% had multimorbidity. There was an independent dose-response relationship between the number of chronic conditions, and absolute (β [95% confidence interval, CI] = -0.05 [-0.07; -0.03]) and relative (hazard ratio, HR [95% CI] = 1.23 [1.17; 1.29]) declines in eGFR. Five patterns of multimorbidity were identified. The Unspecific, low burden pattern had the lowest morbidity burden and was used as the reference category. The Unspecific, high burden, and Cardiometabolic patterns showed accelerated absolute (β [95% CI] = -0.15 [-0.26; -0.05] and -0.77 [-0.98; -0.55], respectively) and relative (HR [95% CI] = 1.45 [1.09; 1.92] and 3.45 [2.27; 5.23], respectively) declines. Additionally, the Cognitive and Sensory pattern showed accelerated relative decline (HR [95% CI] = 1.53 [1.02; 2.31]). No associations were found for the Psychiatric and Respiratory pattern.

Conclusion: Multimorbidity is strongly associated with accelerated kidney function decline in older age. Individuals with cardiometabolic multimorbidity exhibit a particularly increased risk. Increased monitoring and timely interventions may preserve kidney function and reduce cardiovascular risks in individuals presenting with conditions that are characteristic of high-risk multimorbidity patterns.