NPPB and heart failure: There is evidence that cystatin C levels (and their changes with age), a potentially better measure of renal dysfunction than creatinine based measures,15 are associated with physical capability in older adults.16,17 NT-proBNP (N-terminal pro-B-type natriuretic peptide) is a marker of cardiac stress or damage that is associated with cardiovascular disease and heart failure risk across its entire range of measurement,18–21 and with physical activity,22,23 but to our knowledge has not been examined in relation to objective measures of physical capability.