Plasma Klotho and Mortality Risk Among Nursing Home Residents: Results From the SENIOR Cohort

Several authors suggest that circulating klotho, a single-pass transmembrane protein, could be associated with longevity. ^{,  ,  ,}  This study aimed to test the relationship between the level of plasma Klotho and mortality among a specific population of nursing home residents. To address this objective, we measured plasma klotho levels in a longitudinal cohort of 662 nursing home residents, the SENIOR cohort. A sample of 443 subjects from the SENIOR cohort with archived blood samples available at the point of enrollment was included in the current study. This is focused on biomarkers (ie, α-Klotho) at baseline and mortality risk during 2 years of follow-up. The serum levels of α-Klotho were determined according to a solid-phase sandwich enzyme-linked immunosorbent assay kit (Immuno-Biological Laboratories, Takasaki, Japan). The primary outcome was all-cause mortality. The occurrence of death was monitored and recorded over a 24-month follow-up period. Deaths were collected from the medical records, computerized or otherwise, available in the institutions. Other sociodemographic and clinical data were also collected; age, gender, comorbid condition, and drugs consumed were obtained from the subjects' medical record. Anthropometric measurements, such as weight and height, were performed by a clinical research assistant and the body mass index (BMI) was calculated. Smoking status was self-reported. Frailty was measured by the Fried definition. Serum cystatin C was measured by a particle-enhanced nephelometric immunoassay on the BNII nephelometer (Siemens Healthcare Diagnostics, Marburg, Germany) to estimate glomerular filtration rate with the Full Age Spectrum (FAS) equation (FAS_cys).