In the MODEM cohort study, three-hundred and seven people with clinically diagnosed dementia and their carers were recruited on a quota basis to provide equal numbers of people with mild (standardised Mini-Mental State Examination (sMMSE), n = 110), moderate (sMMSE 10–19, n = 100), and severe (sMMSE 0–9, n = 97) cognitive impairment. Participants had a medical diagnosis of dementia made by a specialist mental health service. To be eligible the person with dementia needed to have an identifiable family (or friend) carer or other informant (e.g. a formal/professional carer). There were no exclusion criteria based on comorbidities, age, or type of dementia. The carer was required to self-identify themselves as a carer for the person with dementia. There were no other inclusion or exclusion criteria. Participants were recruited from memory services in Sussex, UK, or self-referral from a national electronic database (Join Dementia Research; https://www.joindementiaresearch.nihr.ac.uk/), community groups, and care homes in the South East of England. People with dementia and their carers were provided with information about the research and invited to participate in the study. A pair of researchers then visited the participants in their home (or another location convenient for the participant). The capacity of the person with dementia was formally assessed by a trained researcher. If the person with dementia did not have capacity to consent, a personal consultee (family member/friend) was identified to advise on whether the person with dementia should take part. For those with capacity, informed consent was obtained. The two researchers then completed a series of measures with the person with dementia and the carer in parallel. For the person with dementia, the following measures were collected: self-reported quality of life (DEMQOL, EQ-5D-3L, CASP-19); proxy-reported quality of life (DEMQOL-Proxy, EQ-5D-3L); severity of cognitive impairment (sMMSE, ADAS-COG); neuropsychiatric symptoms (NPI), depression (Cornell scale); activity limitation (BADLS, OARS); and comorbidities (CCI). Measures collected for the carer were: self-reported measures of quality of life (EQ-5D-3L, SF-12); social isolation (SIS); carer burden (ZCBI); and mental well-being (GHQ). Data were also collected on the use of services and level of help received by formal and unpaid carers and provided by the carer (CSRI) and demographic characteristics of the person with dementia and carer.Dementia has enormous impacts on health and quality of life for people with the illness, their families and other people who care for them. Many people with dementia need care in many areas of their lives, and use a range of health and social care services, as well as getting support from their unpaid carers. Many people with dementia eventually move into care homes. The costs of caring for people with dementia can therefore be high. As the UK population ages over the coming decades, the number of people with dementia will increase considerably. A big challenge facing the country is how to provide high-quality treatment and support to these individuals in ways that are acceptable to them and at a cost considered by society to be affordable. In England, care and support arrangements are guided by the National Dementia Strategy; there are similar commitments in Scotland, Wales and Northern Ireland. Dementia is now getting unprecedented attention: it is a high priority for government, the NHS and local councils. Our research feeds new evidence into this national debate to help decision-makers at many levels in health and social care systems to meet the needs and respond to the preferences of people with dementia and their carers in ways that make best use of the country's resources. We examined existing data to get a clearer understanding of the links between a number of factors: the characteristics of individuals and families, their dementia-related and other needs for care and support, and the services and treatments that could be available to them. We looked at the effects of care, support and treatments on outcomes for individuals and carers - how those interventions can improve their health and wellbeing - and also on the costs of support. With this information we first made projections of how many people there will be with dementia over the period to 2040, what family or other unpaid support they are likely to have available, and what it will cost to provide care services. Second, we examined whether there are better ways to support people with dementia and their carers by introducing new forms of care and treatment. For this part of the research we relied on previous studies that have examined whether these interventions improve health and wellbeing, and at what cost. We identified those 'new ways' by reviewing previous studies of dementia care and treatment (and also reviewing ways to prevent or delay dementia). We looked for evidence on, e.g., medications, cognitive stimulation and other therapies, exercise programmes, nutrition advice, telecare, community initiatives, respite and training for carers. We collected new data from 307 of dyads of people with dementia and their carers, looking at their lives, needs and care at two time points over 12 months. We did not test any interventions with these people. Instead we collected information to help make the best use of data that we could draw from previous studies. We also conducted interviews and focus groups so that we could get 'experiential' evidence, including information on people's preferences. We pulled all this evidence together to simulate what would be likely to happen if interventions with proven benefits for people with dementia and/or their carers were more widely adopted nationally over the coming decades. We were particularly interested in the economic implications: how the future costs of care might be reduced while health and wellbeing are improved. We developed a publicly available tool (accessible via the Web) to enable commissioners, providers, charities, individuals and families to use our evidence to make projections of future costs under different assumptions about population needs, services and treatments. We worked with people with dementia, carers and other potential users of our research at all stages of the project.

Participants had a medical diagnosis of dementia made by a specialist mental health service. To be eligible, the person with dementia needed to have an identifiable family (or friend) carer or other informant (e.g. a formal/professional carer). There were no exclusion criteria based on comorbidities, age, or type of dementia. We recruited 307 dyads of persons with dementia, interviewed them and their carers face-to-face, and followed them up after one year. We used quota sampling to generate balanced numbers: 110 were classified as having mild dementia (scoring 20+ on the standardised Mini-Mental State Examination; sMMSE), 100 had moderate (score 10–19), and 97 severe cognitive impairment (score 0–9). Participants were recruited from memory services in Sussex, UK, or self-referred from a national electronic database (Join Dementia Research; https://www.joindementiaresearch.nihr.ac.uk/), community groups, and care homes in the South East of England. The people with dementia were formally assessed by a researcher to assess capacity to consent to participate in the study. Informed consent was obtained from those persons with dementia with capacity to do so. If they lacked capacity to consent, a personal consultee (family member or friend) was identified to advise on whether the person with dementia should take part. Interviews of the person with dementia and their carer took place simultaneously, with two researchers visiting them in their own household or other agreed location. Capacity to consent was formally evaluated again at the follow-up interview one year later. A series of measures were completed at baseline and one year later: A range of socio-demographic information was collected, including the age and gender of the person with dementia, the type of dementia, their education level and whether they lived in an urban or rural area, the relationship of the carer to the person with dementia, and whether or not the carer was co-resident. Cognitive function - the standardised Mini-Mental State Examination (sMMSE) was used to measure of cognitive impairment, completed by the person with dementia. Neuropsychiatric symptoms - the Neuropsychiatric Inventory (NPI) was used to obtain a carer report of the severity and frequency of 12 neuropsychiatric symptoms associated with dementia. Quality of life – the disease-specific instruments DEMQOL and DEMQOL-Proxy and the generic QoL instruments EQ-5D-3L and EQ-5D-3L-Proxy were used. As stipulated in its manual, only persons with mild or moderate dementia were asked to complete DEMQOL, while all carers were asked to complete DEMQOL-Proxy. People with mild and moderate dementia also completed the CASP-19, a self-report measure of QoL, and carers completed the Short Form Health Survey (SF-12). Activity limitations - carers were asked to assess the level of functioning of the cared-for person using the Bristol Activities of Daily Living Scale (BADLS), rating the person’s ability to complete activities of daily living (ADLs), such as eating and bathing, and instrumental activities of daily living (IADLs), such as cooking and taking medication. Carer burden – the Zarit Carer Burden Inventory (ZCBI) scale was completed by carers. Carer mental wellbeing – the General Health Questionnaire (GHQ-12) was completed by carers reporting on themselves.