Normal GFR varies according to age, sex, and body size; in young adults it is approximately 120 ml/min/1.73 m2 and declines in normal individuals with age. However, a decrease in GFR may also be a marker of kidney disease and precedes the onset of kidney failure; therefore a persistently reduced GFR is a specific diagnostic criterion for CKD. Below 60 ml/min/1.73 m2, the prevalence of complications of CKD increases, as does the risk of cardiovascular disease (CVD). This is a 50% reduction in GFR relative to that of a young adult.