[Definition, epidemiology and prognosis of undernutrition in adults].

DEFINITION, EPIDEMIOLOGY AND PROGNOSIS OF UNDERNUTRITION IN ADULTS Undernutrition is a pernicious and very frequent disease, particularly in hospitals (30 to 40% of adults) where it tends to worsen during the stay. The Covid-19 epidemic has further increased its prevalence. Its pernicious nature is that it is often considered as a symptom accompanying a pre-existing acute or chronic illness and not a disease in its own right. Even in 2022, in addition to the lack of prevention in at-risk populations, it very often remains undetected and/or insufficiently treated. However, it is accompanied by excess mortality and an increased risk of multiple complications: poorer healing, more frequent infections (particularly nosocomial), reduced immunity, increased prevalence of pressure sores, fistula in surgery, poorer quality of life, loss of autonomy, increased duration of artificial ventilation, and more difficult recovery from a pathology, particularly in the elderly. To this must be added an additional cost of care for one given disease or a group of given diseases. Its early diagnosis and management have proven to be effective: reduction of mortality, comorbidities and societal costs.