Dementia could be prevented or delayed by 40 per cent by targeting 12 risk factors throughout life

Experts have increased the number of lifestyle factors known to influence our risk of developing dementia from nine to 12. Taking action on these factors across the life course could delay or prevent the condition in 40 per cent of people who would otherwise develop dementia.

Professor Clive Ballard, of the University of Exeter, is an author on an update to The Lancet Commission on dementia prevention, intervention, and care, which is being presented at the Alzheimer’s Association International Conference (AAIC 2020).

The report highlights nine recommendations for policymakers and individuals to help reduce risk, including providing primary and secondary education for all children, decreasing harmful alcohol drinking, preventing head injury, using hearing aids, protecting ears from high noise levels, and urgently improving air quality.

The potential to reduce the number of people developing dementia is high, and the biggest impact is likely to be seen in low- and middle-income countries where the average age of the population is increasing more rapidly.

The three new risk factors to be added are excessive alcohol intake and head injury in mid-life, and exposure to air pollution in later life. Combined, they are associated with six per cent of the risk of developing dementia– with an estimated three per cent of risk attributable to head injuries in mid-life, one per cent of risk to excessive alcohol consumption (of more than 21 units per week) in mid-life, and  two per cent to exposure to air pollution in later life.

The remaining risk factors are associated with 34 per cent of the risk. These include effectively treating hypertension, diabetes and obesity from mid-life, and exercising from mid-life. The factors associated with the greatest proportion of risk in the population are less education in early life, hearing loss in mid-life, and smoking in later life (seven per cent, eight per cent, and five per cent, respectively). 

Professor Clive Ballard, Dean and Pro-Vice Chancellor of the University of Exeter, said: “Our findings present an exciting opportunity to improve millions of lives across the world by preventing or delaying dementia, through healthier lifestyle to include more exercise, being a healthy weight and stopping smoking; and good medical treatment of risk factors like high blood pressure.  

“One important less well known risk factor is hearing loss in mid-life, with emerging evidence that wearing hearing aids may be protective. This presented an important public health message – if you’re having hearing problems, getting tested in mid life and wearing a hearing aid if needed could have multiple benefits.

“This analysis shows there’s real potential to improve brain health by taking action here in the UK, and to an even greater extent in low and middle-income countries.”

Professor Ballard is one of 28 world-leading dementia experts to author the report, which builds on the nine risk factors identified in the 2017 Lancet Commission, and provides an up-to-date analysis of the best evidence on the prevention of dementia. The new report calls for nations and individuals to be ambitious about preventing dementia and lays out a set of policies and lifestyle changes to help prevent dementia.

Worldwide, around 50 million people live with dementia, and this number is projected to increase to 152 million by 2050, rising particularly in low-income and middle-income countries (LMIC) where around two-thirds of people with dementia live. Dementia affects individuals, their families, and the economy, with global costs estimated at about US$1 trillion annually.

In certain countries, however, the proportion of older people with dementia has fallen, probably due to improvements in education, nutrition, health care, and lifestyle changes, demonstrating the possibility of reducing dementia through preventative measures.

“Our report shows that it is within the power of policy-makers and individuals to prevent and delay a significant proportion of dementia, with opportunities to make an impact at each stage of a person’s life,” says lead author Professor Gill Livingston, University College London, UK. “Interventions are likely to have the biggest impact on those who are disproportionately affected by dementia risk factors, like those in low- and middle-income countries and vulnerable populations, including Black, Asian and Minority Ethnic communities.”

Professor Livingston continued:  “As societies, we need to think beyond promoting good health to prevent dementia, and begin tackling inequalities to improve the circumstances in which people live their lives. We can reduce risks by creating active and healthy environments for communities, where physical activity is the norm, better diet is accessible for all, and exposure to excessive alcohol is minimised.”

To address dementia risk, the authors call for 9 ambitious recommendations to be undertaken by policymakers and by individuals:

• Aim to maintain systolic blood pressure of 130 mm Hg or less in midlife from around age 40 years.
• Encourage use of hearing aids for hearing loss and reduce hearing loss by protecting ears from high noise levels.
• Reduce exposure to air pollution and second-hand tobacco smoke.
• Prevent head injury (particularly by targeting high risk occupations and transport)
• Prevent alcohol misuse and limit drinking to less than 21 units per week.
• Stop smoking uptake and support individuals to stop smoking (which the authors stress is beneficial at any age).
• Provide all children with primary and secondary education.
• Lead an active life into mid, and possibly later life.
• Reduce obesity and diabetes.

These actions are especially important in LMICs where dementia rates are rising more rapidly than in high-income countries. This is a result of increasing life expectancy, and a higher frequency of certain dementia risk factors – such as lower rates of education; high rates of hypertension, obesity, and hearing loss, and rapidly growing rates of diabetes.

Based on their past model including 9 risk factors, the authors estimated that many more cases of dementia could be prevented in LMICs, compared to globally. While globally the 9 risk factors were estimated to contribute to 35 per cent of all dementia incidence, in China they might account for 40, 41 per cent in India and 56 per cent in Latin America.

The authors warn that estimates could be even higher, as they used conservative estimates for the prevalence of these risk factors in these populations, and because they do not account for the three new risk factors. The authors also note that nearly all the evidence for dementia is from studies in high-income countries, so risks might differ for LMICs and interventions might require modifying to best support different cultures and environments. 

The authors note that the modelling for their prevention estimates globally and in LMICs assumes that there is a causal relationship between risk factors and dementia, but were careful to only include risk factors with strong evidence for a causal link.

Report co-author, Professor Adesola Ogunniyi, University of Ibadan, Nigeria, says: “In low- and middle-income countries, the higher prevalence of dementia risk factors means an even greater proportion of dementia is potentially preventable than in “higher-income countries”. In this context, national policies addressing dementia risk factors, like primary and secondary education for all and stopping smoking policies, might have the potential for large reductions in dementia and should be prioritised. We also need more dementia research coming from low- and middle-income countries, so we can better understand the risks particular to these settings.”

In the final section of the report, the authors advocate for holistic and individualised evidence-based care that addresses physical and mental health, social care, and support that can accommodate complex needs. Keeping people with dementia physically healthy is important for their cognition but they often have other illnesses which they may struggle to manage on their own, resulting in potentially harmful preventable hospitalisations.

They note that people with dementia are particularly at risk from COVID-19 (due to age and having pre-existing illnesses, such as hypertension), and that physical-distancing measures can be challenging for dementia patients, who may find it difficult to adhere to the guidelines or distressing to be unable to have contact with carers and family. The authors call for people with unknown COVID-19 status to not be admitted to care homes to protect the existing residents, regular testing of staff and asymptomatic as well as symptomatic residents when there is exposure, not moving staff or residents between homes, and more research into how to protect dementia patients during the current pandemic and future public health emergencies.