The 2024 Lancet Commission has found “compelling evidence” for two new modifiable risk factors for dementia: untreated vision loss and high LDL cholesterol, bringing the total to 14.

Professor Kaarin Anstey, director of the UNSW Ageing Futures Institute and lead of the Brain Health and Dementia Centre at NeuRA, says that while both factors have been known, the evidence is now much stronger.

“These are not new risk factors – the reason they have now made it into the ‘Lancet List’ is that the body of evidence has grown to the point where recommendations about them are stronger. More papers have been published from long-term cohort studies that replicate the associations shown in earlier work,” she explains.

Untreated vision loss

It appears that the cognitive impact occurs when vision loss is ‘untreated,’ she adds.

“It is complicated because there are different associations depending on the cause of the vision loss,” Professor Anstey says.

“Currently, evidence from observational studies indicates that associations are stronger for cataracts and diabetic retinopathy, but not for glaucoma or age-related macular degeneration.”

“There is growing evidence that having cataract extraction reverses or reduces the risk, although this hasn’t been confirmed in large scale randomised controlled trials.”

The bottom line is that maintaining optimal visual function brings cognitive benefits. That means that regular eye checks with their optometrist, interventions to correct vision and treatments for eye disease are important for cognitive health, Professor Anstey says.

High LDL cholesterol

“High LDL in midlife also increases the risk of dementia in late life, which indicates a need to detect and treat LDL in middle-aged adults,” Professor Anstey says.

The 2019 WHO guidelines for reducing risk of cognitive decline and dementia already recommended  managing high midlife dyslipidaemia, Professor Anstey notes. “There are no long term RCTs of statins commencing in mid-life, so this is based on observational data.”

Interestingly, high LDL in late life doesn’t seem to be a risk factor for dementia, she highlights. As such, the WHO guidelines state that treatment in older adults (65 +) should not be specifically initiated to prevent cognitive decline or dementia.

“If GPs are already managing midlife high LDL this should not change practice, but it may impact how GPs discuss high cholesterol with patients,” Professor Anstey says.

Cumulative effect of risk factors

“We know that cardiovascular risk factors cluster together, and that there are interrelationships between some of the risk factors,” Professor Anstey says. Diabetes can lead to vision loss, and both are risk factors for dementia. Some interventions may also address more than one risk factor. For example, physical activity can improve mental health, reduce blood pressure and help manage high cholesterol.

“The more risk factors you have, the greater your risk, but it doesn’t multiply; it is additive,” Professor Anstey explains.

The Lancet report calculates that modifying all 14 risk factors (less education, head injury, physical inactivity, smoking, excessive alcohol consumption, hypertension, obesity, diabetes, hearing loss, depression, infrequent social contact, air pollution, untreated vision loss and high LDL cholesterol) could prevent or delay 45% of dementia cases.

Dr Marita Long, a medical advisor to Dementia Australia, says the research highlights the importance of assessing risk in midlife “to help patients achieve a healthy life as opposed to just a longer life.” She recommends the CogDrisk tool (which was developed by Professor Anstey) and suggests using the 45-49-year-old health check as a Medicare subsidised opportunity to check midlife risk factors for dementia and other chronic diseases.