1: Risk and protective factors for dementia
Risk factors are attributes or exposures that increase the likelihood of a person developing a health condition. Risk factors can be grouped into 2 broad categories: non-modifiable (meaning they cannot be modified in any way) and modifiable (meaning they can be altered or treated with changes in behaviour). Diseases and injuries can also act as risk factors.
Risk factors for dementia include:
- non-modifiable (Chen et al. 2009, AIHW 2023):
- advancing age
- genes associated with dementia (for example, apolipoprotein Eɛ4)
- family history
- modifiable (AIHW 2023, Desmarais et al. 2020, Günak et al. 2020):
- low levels of education in early life
- obesity in midlife
- high blood pressure in midlife
- tobacco smoking
- excessive alcohol consumption
- physical inactivity
- high cholesterol
- high homocysteine
- social isolation
- air pollution
- post-traumatic stress disorder (PTSD)
- diseases and injuries (AIHW 2023):
- cardiovascular disease (including coronary heart disease stroke, and atrial fibrillation)
- chronic kidney disease
- hearing loss in midlife
- traumatic brain injury.
There are several other risk factors that may be associated with an increased risk of developing dementia, but more research is needed on these. They include various lifestyle and biomedical factors (such as prolonged stress, diet, inadequate sleep, and various health conditions) and environmental risks (Anstey et al. 2019). Repeated head injuries can lead to chronic traumatic encephalopathy (CTE) which is a type of brain degeneration that is associated with the development of dementia (Alzheimer’s association). CTE can only be diagnosed after death by examining microscopic changes in the brain and is often identified in brains donated to brain banks such as the Australian Sports Brain Bank (Suter et al. 2022).
The Australian Veterans’ Brain Bank, a sister organisation to the Australian Sports Bank, commenced in 2023 to examine the effect of head injury in veterans (NSW Health 2023). The Australian Former Elite Level Athlete Brain Health Research Program is a longitudinal study that is evaluating how much modifiable risk factors may contribute to the risk of poor health outcomes (AIS 2023). CTE researchers are still learning about its risk factors, causes, symptoms, progression and prevalence. Investigating data sources that could help better understand CTE and its relationship with dementia in Australia would be an important first step to improve data in this area.
Protective factors decrease the chance of a person developing a health condition or may help slow its progression. Protective factors for dementia include higher levels of education and maintaining a socially and cognitively active lifestyle (ADI 2009; Seeher et al. 2011). Actions to address modifiable risk factors include reducing high blood pressure and high cholesterol, eating a Mediterranean style diet, ceasing smoking, limiting alcohol, ensuring sufficient physical activity, healthy sleep patterns and taking protective actions to minimise head injury (Dementia Australia 2021).
Addressing the data gap and improving data
Monitoring dementia risk and protective factors by demographics such as sex, age, geography and cultural background is crucial to understand a population’s risk profile and how this impacts the rate of dementia and trends over time. Having robust and up-to-date information on risk and protective factors is needed to inform primary prevention policies. While effective policies across the entire disease pathway are important, reducing risk and increasing protective factors can reduce, delay or prevent dementia (Alzheimer's Association 2018).
Improved data on dementia risk factors includes better data on the prevalence of risk factors, the strength of association between the risk factor and development of dementia, and research into new risk factors and how risk factors work together. Potential sources for reporting dementia risk and protective factors at a national level are listed below and further sources may emerge over time.
- The Australian Bureau of Statistics (ABS) National Health Survey collects data on population-level health risk factors, including some risk factors for dementia (such as level of highest educational attainment, obesity, physical inactivity, hypertension, smoking, hearing loss and diabetes). National data on other risk factors such as social isolation, head injuries and genetic risk factors are lacking.
- The ABS 2021 Census asked questions on long-term health conditions, including dementia, for the first time. The Census also includes some data relating to dementia risk factors, such as highest educational attainment and household composition (a possible indicator of social isolation).
- The Sax Institute’s Analysis of Population Traits and Risk Factors (ADAPTOR) study links longitudinal data from over 200,000 participants from the 45 and Up Study with data on their use of prescription medications, and hospital, general practitioner (GP) and other health services. It will identify people with dementia and the risk factors that may have contributed to their dementia.
- The Centre for Healthy Brain Ageing is leading the establishment of Dementias Platform Australia. This platform aims to facilitate data sharing between dementia researchers to enhance productivity and reusability of data from contributing studies to enable the development of new insights into ageing, ageing-related diseases and dementia risk.
Genetic testing is currently not a routine part of dementia diagnosis and is usually only performed in rare cases where there is a strong family history of younger onset dementia, to assess a person’s risk of developing dementia. This may change in the future as the understanding of the association between genes and dementia increases (Dementia Australia 2022).
Genetic tests assessing a person’s risk of developing certain types of dementia are not covered under the Medicare Benefits Schedule (MBS), but de-identified data from pathology clinics offering genetic testing could be a potential future data source (subject to relevant privacy provisions) contributing to understanding genetic risk factors and their association with dementia diagnosis, clinical pathways, and outcomes.
Proposed data improvement activities
There are 2 main activities proposed to improve available data on dementia risk and protective factors. These include activities to:
- investigate known and emerging risk and protective factors for dementia and their impacts
- expand dementia risk factors included in Australian Burden of Disease Study analysis.
These activities may involve single projects, or multiple projects aimed at improving data on dementia risk and protective factors. Each activity provides information on the intended outcome, priority rating, level of investment required, timeframe for completion of the activity and who is responsible for undertaking the activity.
This activity involves projects aimed at investigating and analysing dementia risk and protective factors using existing data, and work to develop new data if required. For example, this could include an activity that uses linked data (such as the National Health Survey and 2021 Census within the Multi-Agency Data Integration Product (MADIP) and the ADAPTOR study that capture risk factors that contribute to dementia), existing epidemiological studies and data-sharing platforms (such as Dementias Platform Australia). Risk and protective factors for dementia incidence and progression would be analysed for different population groups and compared to those from large/pooled international studies to appreciate variability across populations groups within (and across) countries.
Relative risks would be calculated, and prevalence of risk factor exposure estimated. The overall contribution of each risk factor on dementia prevalence and mortality (if applicable) in Australia could be estimated. Work to augment existing data collections and specific data developed to assess dementia risks among priority population groups may also be needed where no data are currently available.
Outcome: More comprehensive estimates of the contribution of each risk factor on dementia prevalence and mortality in Australia and how this may change over time, and enable monitoring of risk factors following preventive health initiatives
|Priority Group Data
- Alignment: highly important as provides data on risk and protective factors to estimate the burden of dementia attributable to risk factors in future versions of the Australian Burden of Disease Study (ABDS)
- Foundational data: improves breadth and accuracy of risk factors to improve ABDS and projected prevalence data
- Dependencies: data from external groups and linkage
- Priority group reporting: likely
Level of investment: Low–Medium
Low investment is needed for activities that plan to use existing data. More investment is needed for activities that aim to augment existing data collections, analyse more complex risk factors (such as social determinants of health and diseases-as-risks), or explore risks in priority population groups where greater data development is required.
Timeframe: Short term (<2 years)
Activities could commence now.
Responsible stakeholder: Academic researchers; organisations holding potential sources for reporting dementia risk and protective factors at a national level.
The ABDS 2018 estimated the dementia burden attributable to 6 modifiable risk factors (tobacco use, overweight and obesity, physical inactivity, high blood pressure in midlife, high blood plasma glucose, and impaired kidney function). This is not an exhaustive list of risk factors linked to dementia and only includes risk factors that were measured in the ABDS 2018.
To include additional risk factors in the study, risk factor exposure data are required at the Australian population level (or which could be applied to the Australian population), as well as estimates of the additional risk of developing or dying from dementia (relative risks). Only risk factors that have these data available will be able to be included in this study. Where possible, new data and information developed from the previous activity addressing this data gap would be incorporated into this activity.
Undertaking a specific dementia risk factor burden analysis that includes a broader range of established risk factors for dementia (such as low education levels, air pollution and depression), would allow the contribution of modifiable risk factors to dementia burden in Australia to be better understood. This information can be used to prioritise public health efforts to reduce the incidence of dementia. It should be noted that burden of disease analysis has stringent evidence requirements, which means that evidence accepted in other scientific disciplines may not be included in the ABDS. Further, additional work would be required to assess whether the risk factors and available data used for estimating dementia burden due to risk factors in the general population are applicable for estimating this among First Nations people.
Outcome: Greater inclusion of dementia risk and protective factors data in burden of disease studies allowing greater appreciation of burden and avoidable burden to inform policy and prevention programs
|Priority Group Data
- Alignment: highly important as provides improved data on the contribution of modifiable risk factors for dementia to disease burden in Australia
- Foundational data: for understanding contribution of risks to burden
- Dependencies: outcomes from the first data improvement activity (Activity 1a) would provide data for this activity; this activity is also dependant on ABDS timing and updates
- Priority group reporting: likely – the ABDS currently provides risk factor information by socioeconomic groups, so this work would impact reporting by these population groups; this work could also improve estimates of dementia burden due to risk factors among First Nations people
Level of investment: Low
This activity requires low investment as it utilises existing data and methods developed by the ABDS.
Timeframe: Short term (<2 years)
This activity could commence now and be updated when more evidence and data become available.
Responsible stakeholder: AIHW (National Centre for Monitoring Dementia and teams undertaking the ABDS).
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Suter C, Affleck A, Lee M, Pearce A, Iles L and Buckland M (2022) ‘Chronic traumatic encephalopathy in Australia: the first three years of the Australian Sports Brain Bank’, Medical Journal of Australia, 216:530–531, doi:10.5694/mja2.51420.