This completed observational cohort study evaluates a comprehensive set of clinical and molecular markers of kidney function in two established cohorts of Chinese adults aged 60 years or older. The study assesses markers reflecting glomerular filtration, kidney tubular transport, and kidney endocrine function and evaluates their associations with kidney failure, cardiovascular and cerebrovascular events, and all-cause mortality. It also compares approaches to estimating glomerular filtration rate and develops and internally validates an early-warning model for kidney function decline. Existing baseline and follow-up data and stored serum and urine specimens are used. No intervention or additional study-specific clinical procedure is administered.