Le vieillissement de la population pénale en France pose un véritable problème de santé publique. Or, il existe très peu de recherches sur la santé mentale des détenus âgés. L'objectif de cette étude était d'évaluer l'effet de l'âge et de la durée de détention sur les troubles mentaux et sur les performances cognitives de sujets âgés incarcérés. Nous avons recruté 138 détenus de sexe masculin âgés de 50 ans et plus dans sept établissements pénitentiaires français. Le protocole de recherche comprenait un entretien semi-directif, le Mini International Neuropsychiatric Interview (MINI DSM-IV) pour l'évaluation des troubles mentaux ainsi que la Batterie Rapide d'Efficience Frontale (BREF) et le Mini Mental State Examination (MMSE) pour l'évaluation des performances cognitives. Les résultats ont mis en évidence une prévalence très élevée des troubles mentaux, notamment de la dépression et de l'anxiété, et des troubles cognitifs. Toutefois, la probabilité de survenue de certains diagnostics psychiatriques diminue avec l'avancée en âge (épisode dépressif majeur, agoraphobie, état de stress post-traumatique et anxiété généralisée). Par ailleurs, les estimations effectuées par régression logistique n'ont montré aucun lien significatif entre la durée de détention et les troubles mentaux. En revanche, il existe un lien significatif entre la durée de détention et la déficience cognitive. Ces résultats mettent en évidence une très grande vulnérabilité des détenus âgés sur le plan de la santé mentale et soulignent la nécessité de mettre en œuvre des mesures adaptées de dépistage et de soins pour répondre aux besoins spécifiques de cette frange de la population pénale. Inmate aging is considered to start at the age of 50, which is early in relation to aging in the general population. The aging of the criminal population in France poses a real public health problem. There is very little research on the mental health (mental and cognitive disorders) of older inmates. The objective of this study was to evaluate the effect of age and time spent in prison on mental disorders and cognitive performance of elderly prison inmates. We put forward the hypothesis that age and amount of time spent in prison are associated with the deterioration of older inmates' mental health, that is, an increase in the prevalence of psychiatric disorders and a decrease in cognitive performance. We recruited 138 men aged 50 and over in seven French prisons. The research protocol included a semi-directive interview, the Mini International Neuropsychiatric Interview (MINI DSM-IV) for the assessment of mental disorders, as well as the Rapid Battery for Frontal Efficiency (BREF) and the Mini Mental State Examination (MMSE) for the evaluation of cognitive performance. The average age of the inmates (N = 138) was 59.7 years (range 50–84, SD = 8.02). The average sentence was approximately 13.5 years (SD = 7) and the average time spent in prison was 6.9 years (SD = 5.9). The results showed a very high prevalence of mental disorders, notably depression and anxiety, and cognitive disorders. However, the probability of occurrence of certain psychiatric diagnoses decreases with age (major depressive episode, agoraphobia, post-traumatic stress disorder and generalized anxiety). In addition, logistic regression estimates showed no significant relationship between time spent in prison and mental disorders. However, there is a significant link between time spent in prison and cognitive impairment. Our hypothesis is partially validated. Indeed, age is not associated with mental or cognitive disorders. However, the amount of time spent in prison has an effect on the deterioration of certain cognitive functions. It appears that after the age of 50, it is not chronological age but environmental factors that mainly explain cognitive decline. Our study shows that the longer the detention period, the greater the inmate's cognitive decline. These results highlight the very high vulnerability of elderly prisoners in terms of mental health and emphasize the importance of implementing appropriate detection and care measures to address the needs of this segment of the criminal population. Routine screening for cognitive impairment in all older prisoners should be carried out by caregivers in penitentiary institutions. Furthermore, better follow-up and cognitive assessment of prisoners aged 50 or more and whose length of incarceration exceeds five years could make it possible to detect subjects at risk and to propose appropriate activities to reduce and/or delay the effects of aging in detention. [ABSTRACT FROM AUTHOR]