Alzheimer/’s disease is strongly linked to biological aging and bioenergetic abnormalities. Systemic dysregulation of metabolism is a hallmark of the physiological decline of tissues with age. We aimed to explore untargeted metabolomic profiling of blood samples from amyloid-positive people to distinguish individuals who progressed to cognitive decline from those who remained cognitively intact despite having amyloid deposits in the brain. A minimal signature of 9 metabolites identified decliners and non-decliners of cognitive function in participants with an amyloid load. These findings are of clinical importance as they suggest that a metabolic fingerprint may help to predict patients who will develop cognitive decline. Due to the high prevalence of brain amyloid-positivity in older adults, identifying adults who will have cognitive decline will enable the development of personalized and early interventions. The present invention relates to an in vitro method for predicting cognitive decline in a subject comprising the step of determining the level of at least one metabolite selected in the group consisting of 3-hydroxybutyrate, acetone, triglyceride 48:3, glucose, citrate, succinate, methionine, serine, sphingomyelin d18:1/C26:0 in a biological sample obtained from the subject.