FNDC5 and sarcopenia: Exploratory additional biomarkers will be measured at the same time points in a subgroup of 100 subjects: BDNF, ghrelin, IGF-1, irisin and redox status in plasma as markers of sarcopenia/senescence and oxidative stress, gamma-H2AX in PBMCs as marker of senescence, and amyloid beta aggregates in plasma, urine and erythrocytes as supportive markers of AD.