1.1. Background and Rationale for these Guidelines
Dementia, a group of disorders characterized by a decline from a previously attained cognitive level that affects activities of daily living (ADL) and social functioning, poses one of the greatest global challenges for health and social care in the 21st century.
In 2015, dementia affected 50 million people worldwide (or roughly 5% of the world’s elderly population, i.e. those above the age of 60 years). The number of people with dementia is expected to increase to 82 million in 2030 and 152 million by 2050 with the estimated proportion of the population aged 60 and over with dementia at a given time between 5 to 8%1 because dementia rises exponentially during old age and the world’s population is ageing. These projections assume constant age- and sex-specific prevalence of dementia over time, and, accordingly, the steepest rises are expected especially in low- and middle-income countries (LMIC), where the demographic changes will be more marked.
Dementia is a major cause of disability and dependency among older people worldwide, and it has a significant impact not only on individuals but also on carers, families, communities and societies. Dementia accounts for 11.9% of the years lived with disability due to a noncommunicable disease (NCD) worldwide. Dementia leads to increased costs for governments, communities, families and individuals, and to loss in productivity for economies. The annual global cost of dementia is estimated to be US$ 818 billion (OECD, 2015; WHO, 2017b). Nearly 85% of costs are related to family and social, rather than medical, care (GBD 2015 Neurological Disorders Collaborator Group, 2017). Most health systems are ill-equipped and under-resourced to respond to the current needs associated with dementia. Thus, societal ageing and the associated increases in dementia prevalence will likely have major health-service implications for the care of people with dementia and support for affected families.
There are many different causes and types of dementia. Primary dementias include: dementia due to Alzheimer disease (AD), vascular dementia, dementia with Lewy bodies and frontotemporal dementia (in which the decline in cognitive abilities itself is mostly due to an underlying neurodegenera-tive process and not directly caused by other etiologies). Alzheimer disease is the most common, followed by vascular dementia and dementia with Lewy bodies. Mixed dementia with features of more than one type is also common, especially in older adults, while frontotemporal dementia is a less common form but relatively more frequent before old age.
Secondary dementias are those caused by, or closely related to, some other recognizable disease, such as HIV, head injury, multiple sclerosis, thyroid disorders or vitamin B12 deficiency. In these secondary dementias, cognitive impairment is typically accompanied by symptoms and signs in other organ systems and the treatment focuses on management of the underlying disease.
For the scope of these guidelines we refer to primary dementias. Though early treatment of some diseases may have the potential to prevent the onset of secondary dementias, we are not including these secondary dementias in the scope of these guidelines since there are prevention or appropriate management and treatment strategies for most of these specific diseases and conditions, which effectively reduce dementia-related signs and symptoms. However, late-onset dementia is a heterogeneous and multifactorial condition and some factors (i.e. head trauma, B12 deficiency earlier in life) may also contribute to the development of dementia later in life (not only secondary dementia).
Risk Factors for Dementia
Non-modifiable risk factors for dementia include gene polymorphisms, age, gender, race/ethnicity and family history. Crucially, while age is the strongest known risk factor for cognitive decline, dementia is not a natural or inevitable consequence of ageing. During the last two decades, several studies have shown a relationship between the development of cognitive impairment and dementia with educational attainment, and lifestyle-related risk factors, such as physical inactivity, tobacco use, unhealthy diets and harmful use of alcohol. Further, certain medical conditions are associated with an increased risk of developing dementia, including hypertension, diabetes, hypercholesterolemia, obesity and depression. Other potentially modifiable risk factors may include social isolation and cognitive inactivity. The risk factors included in the scope of these guidelines were chosen based on recent systematic reviews and guidelines, i.e. National Institute of Health and Care Excellence (United Kingdom) (NICE, 2015); the United States of America Agency for Healthcare Research and Quality (AHRQ) systematic review (Kane et al., 2017); the World Alzheimer report 2014 (Prince, et al., 2014) and the report by the Lancet Commission on Dementia Prevention, Intervention, and Care (Livingston et al., 2017). The current focus on modifiable risk factors is justified by their potential to be targeted for prevention of dementia, and/or the delay of the progression of cognitive decline.
Need for these Guidelines
The existence of potentially modifiable risk factors means that prevention of dementia is possible through a public health approach, including the implementation of key interventions that delay or slow cognitive decline or dementia.
In May 2017, the Seventieth World Health Assembly endorsed the Global action plan on the public health response to dementia 2017–2025 (WHO, 2017a). The vision of the action plan is a world in which dementia is prevented and people with dementia and their carers live well and receive the care and support they need to fulfil their potential with dignity, respect, autonomy and equality. The goal of the action plan is to improve the lives of people with dementia, their carers and families, while decreasing the impact of dementia on them as well as on communities and countries. The action plan includes seven strategic action areas, and dementia risk reduction is one of them. The action plan calls upon the WHO Secretariat to strengthen, share and disseminate an evidence base to support policy interventions for reducing potentially modifiable risk factors for dementia. This involves providing a database of available evidence on the prevalence of those risk factors and the impact of reducing them; and supporting the formulation and implementation of evidence-based, multi-sectoral interventions for reducing the risk of dementia. These current guidelines represent the first steps to support countries as they develop approaches to delay or prevent the onset of dementia.
The risk reduction guidelines for cognitive decline and dementia are aligned with WHO’s mandate to provide evidence-based guidance for a public health response to dementia. By supporting health and social care professionals, particularly by improving their capacity to provide evidence-based, multisectoral, gender and culturally appropriate interventions to the general population, including modifiable dementia risk factors that are shared with other NCDs, the risk of developing dementia can be potentially reduced, or its progression delayed. Thus, the guidelines align with WHO’s work in the area of prevention and management of NCDs, which aims to support countries to reduce the incidence, morbidity and mortality of NCDs. WHO has collaborated with a range of stakeholders, including international and national public health agencies working in the area of prevention of NCDs and dementia.
The guidelines are in close conceptual and strategic synergy with other WHO action plans and strategies, i.e. the Comprehensive mental health action plan 2013–2020,2
the Global action plan for the prevention and control of noncommunicable diseases 2013–2020,3 the Global strategy and action plan on ageing and health 2016–2020,4 the Global strategy to reduce harmful use of alcohol5 and the Global strategy on diet, physical activity and health.6 Furthermore, this work is aligned with the WHO move towards making health services more people-centred. Finally, the work will contribute to the attainment of Sustainable Development Goal 3, target 3.8, i.e. achieve universal health coverage, including financial risk protection, access to quality essential healthcare services and access to safe, effective, quality and affordable essential medicines and vaccines for all (UN, 2019).
