Le grand âge donne lieu à des tableaux sémiologiques complexes, où se mêlent des pathologies variées, dont l’expression est liée à influence de l’histoire de vie. Les interrelations entre pathologies psychiatriques et neuro-dégénératives sont de ce fait particulièrement mal connues. Il est pourtant possible de préciser les relations entre état de stress post-traumatique et maladie d’Alzheimer, à travers la caractérisation des symptômes psychiatriques et cognitifs, ainsi que de l’autobiographie du patient. Cette approche est illustrée par le cas d’un homme, ancien combattant de 93 ans. Le recueil de l’histoire de vie, dont les attitudes liées au partage des informations sur les événements traumatogènes, ainsi que des caractéristiques psychopathologiques concernant les deux pathologies selon une perspective vie entière a permis de montrer qu’après plusieurs dizaines d’années d’adaptation aux souvenirs traumatiques, la perte d’autonomie cognitive était associée à l’émergence d’un état de stress post-traumatique retardé.

Old age leads to complex semiologies, mixing several diseases, whose expression is linked to the influence of life history. Accordingly, even if neurodegenerative diseases today constitute one of the main diseases affecting aging people, the interrelations between neurodegenerative and psychiatric disorders are particularly poorly understood. Two assumptions coexist about the interrelation between post-traumatic stress disorders and dementias. According to the first one, post-traumatic stress disorders contribute or worsen neurodegenerative disorders. The second one supposes that dementias lead to late-onset post-traumatic stress disorders. In the absence of regular life-long health follow-up, the entanglement of both symptomatologies in the oldest age people makes impossible to valid one or the other or both. It is however possible to clinically precise the relations between post-traumatic stress disorder and Alzheimer's disease through the characterization of cognitive and psychiatric symptoms, and also through the collection of patient's autobiography. This approach is illustrated by the case of a 93-year-old veteran, living in a nursing retirement home. His neurodegenerative disorder had altered his memory and his executive abilities. His discourse was coherent, with temporal distortions and intrusions of real recent events. He presented all diagnostic criteria for post-traumatic stress disorder, with numerous repetitions of intrusive memories of war events in which he was powerless, amnesia for some elements of the trauma, and major efforts to avoid thinking about wartime. Yet, he had demonstrated a willingness to share his memories with his family as soon as he returned from war. The collection of life story, including information sharing behaviors about the traumatogenic events, and psychopathology characteristics of both pathologies in a life-course perspective showed that the Alzheimer's disease revealed a post-traumatic stress disorder. After several decades of adaptation to traumatic memories, cognitive autonomy loss was associated with the emergence of late-onset post-traumatic stress disorder.