Dementia is now the leading cause of death for Australian women and is highly prevalent at older ages, with approximately 30 per cent of adults aged over 85 being diagnosed with the condition and a total of 6 – 8 per cent of adults over the age of 65. Currently there are no effective treatments or cures for the diseases that cause neurodegenerative changes leading to dementia syndromes. In late-life it is recognised that most dementias are ‘mixed’. This means that vascular and Alzheimer’s pathology are likely to be present and possibly other causes of neurodegeneration.
Risk reduction has been recognised by the World Health Organization as a key strategy in reducing future incident dementia, given the number of modifiable risk factors for which there is accumulating observational and clinical trial evidence. While significant gaps remain in our knowledge, the public health benefits of dementia risk reduction are incontrovertible, because several modifiable risk factors overlap with other key chronic disease areas such as heart disease, stroke, diabetes and cancer. Risk reduction for dementia is likely to also promote healthier ageing and reduce risk of frailty.
Whilst the mantra of ‘what’s good for the heart is good for the brain’ is largely true, there are some nuances in the evidence regarding cardiovascular risk factors and brain health that distinguish dementia risk reduction from cardiovascular risk reduction. For example, long-terms studies show that having high cholesterol, hypertension or being overweight in midlife increase the risk of dementia in late life. However, the association between these risk same factors and risk of dementia when they are present in older adults, is less clear.
Obesity in old age, for example, does not appear to increase risk of dementia. Some of the complexity in interpreting the evidence stems from ‘reverse causation’ – that is changes that occur in the risk factors due to accumulation of neuropathology and brain changes that are prodromal to dementia. Weight loss may precede Alzheimer’s disease by up to eight years which confounds observations in cohort studies. This two-way interaction between neurodegenerative disease and vascular risk factors is an area of current investigation.
With the burgeoning of evidence on dementia being published, and some of it being inconsistent or from populations with different characteristics, it can be at times difficult to know where to focus, which studies to pay attention to and which evidence is applicable here in Australia. Our team has therefore focused on establishing the quality of the evidence base and risk factors for which there are solid systematic reviews that show replication of the risk factors in different populations.
We examined factors such as the source of the evidence, the age at which the populations were first examined for risk factors and the length of time over which they were followed for dementia outcomes. We also consider factors such as potential reverse causation and related guidelines for risk factors for multiple chronic disease areas.
The recent publication of guidelines on dementia risk reduction in primary care was based largely on our review of the observational evidence published in 2019. We also took into account clinical trial evidence for medications.
In summary, the guidelines recommend the following lifestyle advice:
- smoking cessation
- advise consumption of alcohol according to NHMRC guidelines
- increase physical activity according to national guidelines
- healthy diet following the national guidelines with nutrient pattern similar to the Mediterranean diet
- increase social engagement and cognitively stimulating activities, if these are low.
The guidelines recommend the following medical advice for reducing medical risk factors for dementia:
- treat sleep disorders as appropriate
- treat depression
- advise maintaining weight in the normal BMI range, particularly in middle age
- treat diabetes, hypertension, atrial fibrillation as per clinical recommendations as these all increase risk of late-life dementia
- apart from antihypertensives, no other medicines have RCT evidence to show they reduce risk of cognitive decline or dementia
- These medicines are not indicated for cognitive symptoms (HRT, statins, anti-inflammatories).
- Benzodiazapenes and anticholinergic medicines have been shown to increase risk of late-life cognitive decline or dementia and should be deprescribed where possible.
Finally, this is an area of active research and we expect the guidelines to be refined regularly. For more information click here.
Prof Kaarin Anstey and Dr Ruth Peters
Dementia Centre for Research Collaboration
University of New South Wales and Neuroscience Research Australia
