Maria J. Marques ^1,2* Bob Woods ³ Hannah Jelley ³ Liselot Kerpershoek ⁴ Louise Hopper ⁵ Kate Irving ⁶ Anja Bieber ⁷ Astrid Stephan ⁷ Anders Sköldunger ⁸ Britt‐Marie Sjölund ⁸ Geir Selbæk ⁹ Janne Røsvik ⁹ Orazio Zanetti ¹⁰ Daniel M. Portolani ¹⁰ João Marôco ¹¹ Niels Janssen ⁴ Eva Y.L. Tan ^12,4 Marjolein de Vugt ⁴ Frans Verhey ⁴ Manuel Gonçalves-Pereira ^13,2

• ¹ NOVA National School of Public Health, NOVA University Lisbon, Lisbon, Portugal
• ² Comprehensive Health Research Center (CHRC), Laboratório Associado REAL, Lisbon, Portugal
• ³ Dementia Services Development Centre (DSDC) Wales, School of Medical and Health Sciences, Bangor University, Bangor, United Kingdom
• ⁴ Department of Psychiatry and Neuropsychology and Alzheimer Centre Limburg, School for Mental Health and Neurosciences, Maastricht University, Maastricht, Netherlands
• ⁵ School of Psychology, Dublin City University, Dublin, Ireland
• ⁶ School of Nursing, Psychotherapy and Community Health, Dublin City University, Dublin, Ireland
• ⁷ Institute for Health and Nursing Science, Martin Luther University Halle-Wittenberg, Halle (Saale), Germany
• ⁸ Division of Neurogeriatrics, Department of Neurobiology, Care sciences and Society, Karolinska Institutet, Sweden, Stockholm, Sweden
• ⁹ Norwegian National Centre for Ageing and Health, Vestfold Hospital Trust, Tønsberg, Department of Geriatric Medicine, Oslo University Hospital, Faculty of Medicine, University of Oslo, Oslo, Norway
• ¹⁰ IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy
• ¹¹ William James Center for Research, Instituto Superior de Psicologia Aplicada – Instituto Universitário (ISPA-IU), Lisboa, Portugal, Lisboa, Portugal
• ¹² Institute for Mental Health Care, GGzE, Eindhoven, Eindhoven, Netherlands
• ¹³ Faculdade de Ciências Médicas, NOVA Medical School, NOVA University Lisbon, Lisbon, Portugal

Objective: The quality of the relationship between persons with dementia and family carers influences health and quality of life outcomes. Little is known regarding those at higher risk of experiencing a decline in relationship quality, who could potentially benefit the most from interventions. We aimed to identify these risk profiles and explore the underlying factors. Methods: We applied a latent profile analysis to relationship quality data from a 1-year follow-up of 350 dyads of persons with dementia and their informal carers from the Actifcare cohort in eight European countries. Assessments included sociodemographic, clinical, functional, psychosocial and quality of life measures. Relationship quality was assessed with the Positive Affect Index. A discriminant analysis explored factors influencing the risk profiles. Results: There were two relationship quality profiles among persons with dementia (gradually decreasing, 74.0%; low but improving, 24.6%) and two among carers (steadily poor, 57.7%; consistently positive, 42.3%). The ‘gradually decreasing’ profile (persons with dementia) was related to their levels of dependence and unmet needs, along with carers’ social distress and negative feelings, lower baseline RQ and sense of coherence. The ‘steadily poor’ profile (carers) was influenced by their social distress and negative feelings, lower sense of coherence and perceived social support. These two predominant profiles showed significant decreases in quality-of-life over one year. Conclusions: Specific profiles of persons with dementia and their carers are at risk of worse relationship quality trajectories. By considering modifiable related factors (e.g., carers’ stress), our findings can help develop tailored, effective interventions.