• Risk factors:
• Aging, even during the fifth decade of life, is associated with measurable cognitive decline and an increasing incidence of dementia (2). Thus, any study that follows older people longitudinally will observe cognitive decline and incident dementia (1).
• Critical illness after surgery is often associated with multi-organ dysfunction, including neurological impairment. When patients suffer a serious postoperative complication, such as pneumonia or acute renal failure, subsequent persistent cognitive decline, or incident dementia might be ascribed to the surgery, whereas the root cause of brain injury might be the pathological processes associated with critical illness (1).
• Underlying comorbidities, such as vascular disease, are associated with cognitive decline and dementia (3).

Future risks:

• Delirium: In the early postoperative phase, typically 24–96 h after surgery, patients often experience delirium, an acute and fluctuating cognitive dysfunction that is associated with morbidity and mortality, with reduced function and independence (4). Delirium occurs in 10–70% of patients older than 65 undergoing major surgical procedures (5).
• Early postoperative cognitive decline: POCD lasting up to 3 months occurs in up to 10% of elderly patients (6). Indeed, studies have suggested that early POCD affects all age groups, but resolves faster in younger patients (1).
• Persistent postoperative cognitive decline: persistent POCD is arbitrarily defined as POCD longer than 6 months. In general, the determination of persistent POCD is complicated by limitations of statistical analysis and length of follow-up (1).
• Postoperative cognitive improvement (POCI): POCI could conceivably occur when surgery improves health, enhances quality-of-life, decreases inflammation, or alleviates pain (1).