Background: The relationship between kidney function and depressive symptoms among elderly people has been rarely investigated in settings of the general population. The aim of our study was to examine the association of serum cystatin C (cysC) and impaired kidney function with geriatric depressive symptoms among older people living in a rural community in China.

Methods: This population-based cohort study included 1440 individuals (age60years) who were recruited for the Confucius Hometown Aging Project in 2010-2011; of the 1124 persons who were free of depressive symptoms, 669 (59.5%) were re-examined in 2014-2016. At baseline, data on demographics, lifestyle factors, health conditions, and medical history were collected through interviews, clinical examinations, and laboratory tests. We defined impaired kidney function as the cystatin C-based estimated glomerular filtration rate (eGFR(cysC)) <60ml/min/1.73m(2), and depressive symptoms as a score5 on the 15-item Geriatric Depression Scale. Data were analyzed using multiple logistic and Cox proportional-hazards models.

Results: Of the 1440 participants, 316 (21.9%) were defined to have geriatric depressive symptoms at baseline. Serum cysC levels of 1.01-1.25 and>1.25mg/L (vs. 1.00mg/L) were associated with a multiple-adjusted odds ratio (OR) of 1.41 (95% CI 1.01-1.97) and 3.20 (2.32-4.41), respectively, for having geriatric depressive symptoms (P-trend<0.001). Of the 669 people who were free of depressive symptoms at baseline, 157 had incident depressive symptoms at the follow-up examination. The multiple-adjusted hazard ratio (HR) for incident depressive symptoms were 2.16 (95% CI 1.43-3.27) for serum cysC >1.25mg/L (vs. <1.00mg/L). Impaired kidney function was cross-sectionally (multiple-adjusted OR=2.95; 95% CI 2.22-3.92) and longitudinally (multiple-adjusted HR 1.54; 95% CI 1.03-2.30) associated with an increased risk of geriatric depressive symptoms.

Conclusion: Elevated serum cysC levels and impaired kidney function are associated with an increased risk of geriatric depressive symptoms among Chinese older people living in a rural community.