A major shift in medical thinking has transformed the view on dementia from an unavoidable fate to a condition that can be substantially influenced by lifestyle and medical interventions. The WHO's latest guidelines mark a sharp departure from a 2010 National Institutes of Research conference, which stated there was no moderate-quality evidence linking any modifiable factor to reduced Alzheimer's risk.
Hearing loss and high cholesterol are now identified as the two biggest known modifiable factors, according to the Lancet Commission, each representing a potential seven per cent drop in risk if addressed. The WHO guidelines note that untreated hearing loss contributes to decreased social engagement, mental wellbeing and physical activity, which can increase the risk of cognitive decline. Similarly, high levels of low-density lipoprotein (LDL) cholesterol can cause vascular damage and an increase in amyloid and tau proteins in the brain.
Other significant factors include high blood pressure, stroke, diabetes, obesity and untreated vision loss, which has recently been recognised as a risk factor. Many of these conditions are treatable through lifestyle changes, medication, glasses and hearing aids.
Professor Henry Brodaty, Senior Australian of the Year and director of the University of NSW's Centre for Healthy Ageing, said the change in understanding has been dramatic: from "half a page in textbooks" in the 1970s to the world's largest dementia research conference attracting more than 10,000 attendees this year. "If you think there's nothing you can do to prevent dementia, think again - because there's plenty you can do," he said.
Professor Anstey expects the proportion of modifiable risk will grow as more factors are identified. Associate Professor Dr Marita Long, a GP and honorary medical advisor at Dementia Australia, has advocated for dementia risk assessments to become a standard part of primary care.