Loneliness as an Interface Between Alzheimer's Disease and Suicidal Behaviour: A Systematic Review, Meta-Analysis and Meta-Analytic Factor Analysis.

Loneliness is an epidemic affecting mental health across all demographics. It is linked to mental disorders, such as anxiety and depression, and despair, highlighting a significant public health issue as persons feel more disconnected in a connected world. This study aims to investigate the relationship between loneliness, Alzheimer's disease and suicidal behaviour. This review was systematised in a dichotomous manner. Therefore, two systematic reviews were initially carried out following the PRISMA statement. The loneliness was understood as feeling lonely. One group searched for associations between loneliness and Alzheimer's disease and the other between loneliness and suicidal behaviour, with a consecutive meta-analysis. After that, it was searched for between the two groups to seek loneliness, such as an interface in meta-analytic factor analysis. Depression is the most studied and cited factor associated with loneliness as a link between Alzheimer's disease and suicide. Loneliness demonstrated association with Alzheimer's disease (OR = 1.89, 95% CI 1.57-2.28; p < 0.001); suicidal ideation (OR = 2.17, 95% CI 1.88-2.51; p < 0.001); suicidal planning (OR = 2.36, 95% CI 1.91-2.92; p < 0.001); suicide attempt (OR = 2.54, 95% CI 2.13-3.04; p < 0.001); and suicide (OR = 4.9, 95% CI 4.4-5.5; p < 0.001). Entrapment, hopelessness, insomnia and stress demonstrated significative correlation (r > 0.40; p < 0.001) with loneliness in the interface between AD and suicidal behaviour. Loneliness has been identified as a comorbid factor between AD and suicide. To prevent both AD and suicide, it is essential to monitor levels of stress, insomnia, feelings of entrapment and hopelessness. The triad of loneliness, hopelessness and insomnia seems to represent the greatest risk profile.