Dementia is an umbrella term for a range of neurological disorders usually characterised by the progressive loss of memory and cognitive abilities (Winblad et al., 2016; World Health Organization, 2017). The most common form of dementia is Alzheimer's disease (AD) which accounts for 60-70% of all dementia cases (World Health Organization, 2017). Other forms of dementia include vascular dementia, caused by impaired blood flow to the brain; Lewy body dementia, associated with an abnormal build-up of masses of proteins; and frontotemporal dementia (World Health Organization, 2017). While these forms of dementia together with AD are medically distinct, they often coexist and the boundaries between them are usually indistinct (World Health Organization, 2017).

Dementia has been recognised as a public health priority in both developed and developing countries. Dementia is currently the seventh leading cause of death among all diseases globally (GBD 2019 Collaborators, 2021) and in developed countries was ranked second in Australia in 2020 (Australian Bureau of Statistics, 2020), and sixth in the USA (Kochanek et al., 2020). Globally, an estimated 1.62 million people died from dementia in 2019 (GBD 2019 Collaborators, 2021). In Denmark, dementia is believed to be the fourth most common cause of death, after heart diseases, cancer and respiratory diseases (Taudorf et al., 2021b; Vestergaard et al., 2020). In 2015, 47.47 million people were living with dementia worldwide (World Health Organization, 2015). Currently, over 50 million people are living with dementia and the figure is expected to triple to 152 million in the next three decades (Alzheimer's Disease International, 2019). Dementia cases in European Union member states account for nearly 18.2% (or 9.1 million cases) of global cases (OECD/EU, 2018). An estimate from a recent study shows 126,734 people were living with dementia in Denmark in 2013 representing 4.5% of individuals aged 50 years and above (Fann et al., 2018). The risk factors for dementia are multifaceted including socioeconomic status, environmental risk exposures, biological and lifestyle and behavioural factors (Chen et al., 2017; GBD 2016 Dementia Collaborators, 2019; Mukadam, Sommerlad, Huntley, & Livingston, 2019; Murayama et al., 2019; Wimo et al., 2017).

Current dementia research has paid little attention to how individual and contextual socioeconomic factors and demographic factors inform the spatial risk distribution patterns of dementia. Understanding factors that contribute to an elevated risk of dementia based on where one lives is crucial for addressing spatial inequalities in health outcomes as well as designing intervention measures for tackling dementia. The longitudinal Danish registries provide a rich resource, enabled via individual data linkage to link health records and individual-level data from the population registers across the whole life course (Pedersen, 2011; Pedersen et al., 2006). The insights from using geospatial analytic techniques, such as Bayesian spatial disease mapping, are vital for enhancing our understanding of geographical differences in the risk of dementia.

In this study, we explore the spatial risk patterns of dementia across Denmark using individual-level data and geocoded residential addresses. Specifically, the study sought to examine the spatial risk pattern of dementia in Denmark, accounting for individual and neighbourhood-level socioeconomic factors.