Introduction/Background: Suicide in older people is a historically neglected research area. Local audits had suggested that Cornwall had a higher than average suicide rate, and people aged 75 years and over appeared to be at particularly high risk. Heterogeneity between studies and variations in presenting suicide statistics can make comparison of rates difficult. Aims: The study aimed to explore in depth the epidemiology of suicide in elderly people in Cornwall, to develop an understanding of the risk factors (including sources of stress), suicide methods, locations, and warnings, and consequently to identify potential preventive strategies. Methods: A mixed methods approach was taken, combining quantitative epidemiological study of suicide using Office for National Statistics (ONS) Public Health Mortality Files with qualitative retrospective case study analysis using coroner’s records and local audit database. All completed suicides (and some systematically selected open verdicts) in people aged 75 years and over occurring in Cornwall between 2006 and 2010 were included. A questionnaire survey of rural community dwelling people aged 75 years and over (n = 49) in a part of Cornwall was also carried out to identify the main sources of stress associated with ageing in the local area. Results: Some discrepancies in the number of open verdicts reported by the coroner and ONS were noted. Although suicide in the over 75 age group was responsible for only 0.3 % of all-cause mortality in males and 0.1 % in females, the overall suicide rate in this age group in Cornwall was significantly higher than the average for the UK, with a Standardised Mortality Ratio of 172 (95 % CI 123 to 236). Males aged between 75 and 84 years had the highest suicide rate in Cornwall (mean of 25.8 deaths per 100,000 population, 95 % CI 1.1 to 50.5). Jumping from a height and suffocation were the most frequently used methods, accounting for 8 and 7 of the 34 deaths respectively. 28 of the 34 suicides took place at home. Depressive illness, physical illness and bereavement were the most commonly identified risk factors. Concerns revealed in survey responses were closely related to suicide risk factors, including fear of losing independence, bereavement, physical illness, isolation, and fear of becoming a burden. Warnings included previous self-harm or attempted suicide, suicide ideation or plans, behavioural changes and researching euthanasia. Discussion: As persons aged 75 and over are at significantly higher risk of suicide in Cornwall than other regions, there is a need to reduce the number of suicides in this group. Possible preventive measures include reducing access to means (in particular for jumping incidents), earlier detection of depression in the physically ill, bereavement counselling, more social groups and support groups in rural areas, helping people to retain their independence, and a change in societal attitudes towards elderly people. There may also be a need to improve the accuracy of suicide statistics. Conclusion: Health services, councils, voluntary groups and the community as a whole should work together to prevent suicide in older people. Future controlled studies should assess the effectiveness of interventions and focus more on differences between subgroups of elderly people.

L’acier inoxydable est un alliage important pour le développement technique d’une société moderne; cela a été découvert au début du 20ème siècle. Cependant, leur système d'alliage de base, Fe-Cr, est affecté par une lacune de miscibilité à basse température (<600 °C) présent dans le diagramme de phases. Les alliages présentant une lacune de miscibilité dans leur diagramme de phase ont tendance à se décomposer. Ce phénomène également connu sous le nom de "fragilisation à 475 °C", est d’une importance technique, car la décomposition modifie les propriétés mécaniques de ces alliages; dans ce cas présente, par la perte de ductilité et de résistance aux chocs. La tendance à la décomposition augmente avec la diminution de la température, ce qui limite la température de service supérieure à environ 300 °C, limitant ainsi la durée de vie de ces alliages. Étant donné que la fragilisation peut provoquer une défaillance soudaine de ces alliages, cet aspect nuit à leur utilisation en tant que composants structurels dans les secteurs du transport et de l’énergie. La décomposition des alliages Fe-Cr pose un défi aux techniques de caractérisation traditionnelles, car les variations de composition se produisent à l'échelle nanométrique. Par conséquent, la sonde atomique tomographique de pointe a été utilisée pour étudier ces variations de composition à l'échelle atomique en 3D. La modélisation atomistique corrélative a été utilisée pour améliorer davantage la compréhension du processus de décomposition dans ces alliages ; ce modèle était basé sur la théorie de la fonction de densité atomique. Pour émuler la décomposition améliorée du matériau, causée par la température et/ou une charge externe, la décomposition dans ce projet est stimulée par une température de service supérieure à la normale. Dont la nécessité de connaître la limite exacte de la lacune de miscibilité. Ainsi, la nécessité d'évaluer la limite supérieure de température de cette décomposition dans le système Fe-Cr est née de résultats non concluants des analyses de la littérature existant. Par conséquent, un four de haute précision en combinaison avec une sonde atomique tomographique a été utilisé pour étudier la décomposition et l’agglomération dans le système Fe-Cr d’une manière plus précise que jamais. En outre, d’explorer en détail l’emplacement de la limite de la lacune de miscibilité. La décomposition de ces alliages au cours du vieillissement modifie les propriétés mécaniques. Ainsi, en raison de leur utilisation en tant que composants structurels, le comportement de décomposition dû au vieillissement a été étudié, ainsi que le vieillissement dû à la charge externe. Cette dernière situation se rencontre également dans des applications réelles pendant le service, émulées par le vieillissement dû à la pression en utilisant une simple force de traction. Afin d'examiner en détail l'effet de la pression externe, l'orientation du grain par rapport à la direction de traction a été prise en compte lors d'un simple vieillissement thermique et lors de l’application d’une force de traction continue. Ainsi, l'orientation cristallographique et les niveaux de charge ont été pris en compte pour leur effet sur le processus de décomposition/dégradation. / Stainless steel is an important alloy for the technical development of a modern society, they were discovered in the early 20th century. However, their base alloying system, Fe-Cr, is affected by a low temperature (<600°C) miscibility gap present in the phase diagram. Alloys with a miscibility gap in their phase diagram tend to decompose. This phenomenon is also known as the “475°C embrittlement”, it is of technical importance as decomposition alters the mechanical properties of these alloys, in this specific case, by loss of ductility and impact toughness. The tendency to decompose increases with decreasing temperature, restricting the upper service temperature to around 300°C and limiting the service lifetime of these alloys. Because embrittlement can cause sudden failure of these alloys, this phenomenon is detrimental to their use as structural components in transportation and energy industry. The decomposition of Fe-Cr alloys poses a challenge for traditional characterisation techniques, as composition variations occur at the nanoscale. Therefore, the state-of-the-art atom probe tomography have been utilised to study these composition variations at the atomic scale in 3D. Correlative atomistic modelling has been used to further enhance the understanding of the decomposition process in these alloys, this model was based on atomic density function theory. To emulate enhanced decomposition of the material, caused by temperature and/or an external load, decomposition in this work is stimulated by a higher than the normal service temperature. Hence, a need to know the exact limit of the miscibility gap. Thus, a need to evaluate the upper-temperature limit of this decomposition in the Fe-Cr system arose from inconclusive results in the literature. Hence, a high precision furnace in combination with atom probe was utilised to study decomposition and clustering in the Fe-Cr system more accurately than ever before. Furthermore, to explore in detail the location of the limit of the miscibility gap. The decomposition of these alloys during ageing alter the mechanical properties. Thus, due to their use as structural components, the decomposition behaviour during ageing was investigated, as well as ageing during external load. This last situation is also encountered in real applications during service, mimicked by stress-ageing using a simple tensile force. In order to in detail investigate the effect of the external stress, grain orientation with respect to the tensile direction was considered during simple thermal ageing, and during the constantly applied tensile force. Thus, crystallographic orientation and load levels were considered for their effect on the decomposition process.