Dementia is a common disorder among the ageing population, particularly in developed countries (Asada, 2012; Currais et al., 2015). Previous studies have indicated an association between demographic structure and dementia (Fisher et al., 2011; Tom et al., 2015; van der Linde et al., 2010). For example, older people are a major vulnerable population with high prevalence of dementia, especially those with an unhealthy diet, low mobility and a low level of physical activity (Beydoun & Kivimaki, 2020; Najar et al., 2019). As activities of daily living as well as mobility could affect both dementia and quality of life (Beydoun & Kivimaki, 2020), numerous studies have also investigated the linkage between dementia and quality of life (Banerjee et al., 2009; Bowling et al., 2015; Hurt et al., 2008), specifically in the local context of how physical activities improve the wellbeing of older people with this disease (Algar et al., 2016; Scarmeas et al. 2009). In addition, human behaviors, activities of daily living and spatial mobility of older adults could also be affected by the neighboring environment of their residences (Cerin et al., 2013), therefore, this has also led to a research trend of investigating influences of built and social environments on the prevalence of dementia (Wu et al., 2015). For example, recent studies have found that green space as a built environmental factor reduces dementia and its associated diseases (de Keijzer et al., 2016; White et al., 2018; Wu et al., 2015). Some studies have also documented the adverse impacts of socioeconomic and racial problems on these diseases (Cadar et al., 2018; Chiao et al., 2014; Cook, 2019; Van De Vorst et al., 2016; Yaffe et al., 2013), and other studies have found that long-term air pollution (e.g. traffic-related air pollution) can negatively influence cognitive function (Chen et al., 2017a; Chen et al., 2017b; Lee et al., 2019; Hamid et al., 2010; Oudin et al., 2015; Power et al., 2010; Shin et al., 2018; Zhang et al., 2018). There are also studies describing the short-term risks of dementia, due to extreme weather or daily variation of temperature, and air quality (Ho & Wong, 2019; Linares et al., 2017; Wei et al., 2019). In the above-summarized literature, detailed linkages between exposure to such factors and dementia have been discovered.
Despite the research trend above, the fatal effects of dementia and its relationships with the social and geophysical environment have rarely been discussed, especially in the context of a high-density Asian city. Although mortality associated with dementia may not be as high as other chronic diseases such as respiratory diseases and cancers, there are still remarkable death counts due to dementia in high-density Asian cities. For example, approximately 2.1% of male deaths and 4.0% of female deaths were from dementia in 2016, based on Public Health Information and Statistics of Hong Kong (https://www.healthyhk.gov.hk). Furthermore, dementia was one of the two brain-related diseases recognized among the “ten leading causes of death” for both males and females in the same database. This indicates that dementia can be a significant factor causing fatal effects to those who are aged over 30 and whose dementia is not due to genetic issues. While it is still important to evaluate the survival population with dementia, it is also essential to study dementia mortality in order to better develop protocols for health surveillance and community planning.
Furthermore, as Hong Kong is a city with high-density living and a compact environment (Ho et al., 2019b; Peng et al., 2017), it is expected that “population stress” has been occurring due to the local population growing faster than the available land (Chi & Ho, 2018). Based on the perspective of human ecology, this population growth can also influence the change of urban form and natural environment (Clement et al., 2015). Therefore, it is important to enhance the understanding of the human-environment nexus across a high-density city, in order to create a “healthy city” that can protect all ages and all vulnerable populations (Ho et al., 2017; Woo et al., 2017), including people with dementia at different ages.
We hereby develop a territory-wide register-based study to evaluate the potential influences of social and environmental burdens on dementia mortality in a high-density Asian city (Hong Kong). The objectives of this study include evaluating the links between age-specific dementia mortality in Hong Kong and 1) individual-level socioeconomic characteristics, 2) community-level socioeconomic characteristics, 3) short-term environmental changes, and 4) long-term environmental deprivation.