40% of dementia cases could be prevented or delayed by targeting 12 risk factors throughout life, says study
Experts have added excessive alcohol intake, head injury in midlife and exposure to air pollution in later life to a list of key modifiable risk factors for dementia
Around 50 million people live with dementia worldwide and this number is projected to increase to 152 million by 2050, rising particularly in low-income and middle-income countries (LMICs) where around two-thirds of people with dementia live. An international research team, however, estimates that by modifying or targeting 12 risk factors throughout life, one could prevent or delay 40% of dementia cases. Dementia is a syndrome, usually of a chronic or progressive nature, in which there is deterioration in memory, thinking, behavior and the ability to perform everyday activities.
Led by 28 leading dementia experts, the report builds on the nine risk factors identified in the 2017 Lancet Commission. Excessive alcohol intake, head injury in midlife, and exposure to air pollution in later life have now been added to the list of key modifiable risk factors for dementia, thus expanding the number of preventable causes from nine to 12 factors that span from childhood to later life.
Combined, the three new risk factors are associated with 6% of all dementia cases -- with an estimated 3% of cases attributable to head injuries in midlife, 1% of cases to excessive alcohol consumption (of more than 21 units per week) in midlife, and 2% to exposure to air pollution in later life. The remaining risk factors are associated with 34% of all dementia cases. The factors associated with the greatest proportion of dementia cases in the population are less education in early life, hearing loss in midlife, and smoking in later life -- 7%, 8%, and 5%, respectively.
“Overall, a growing body of evidence supports the nine potentially modifiable risk factors for dementia modeled by the 2017 Lancet Commission on dementia prevention, intervention, and care: less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, and low social contact. We now add three more risk factors for dementia with newer, convincing evidence. These factors are excessive alcohol consumption, traumatic brain injury, and air pollution,” write authors in the analysis published in The Lancet. “We have completed new reviews and meta-analyses and incorporated these into an updated 12 risk factor life-course model of dementia prevention. Together the 12 modifiable risk factors account for around 40% of worldwide dementias, which consequently could theoretically be prevented or delayed,” the team suggests.
Dementia affects individuals, their families, and the economy, and the latest estimates suggest that the cost of dementia is $1 trillion annually. According to the authors, the proportion of older people with dementia has fallen in certain countries, probably due to improvements in education, nutrition, healthcare, and lifestyle changes, demonstrating the possibility of reducing dementia through preventative measures. They have called for nations and individuals to be ambitious about preventing dementia and lays out a set of policies and lifestyle changes to help prevent dementia.
“Our report shows that it is within the power of policymakers 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. 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,” says lead author Professor Gill Livingston, University College London, UK. “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 minimized,” adds Professor Livingston.
To address dementia risk, the report recommends ambitious goals to be undertaken by policymakers and by individuals. This includes the aim to maintain systolic blood pressure of 130 mm Hg or less in midlife from around age 40 years, encouraging the use of hearing aids for hearing loss and reducing hearing loss by protecting ears from high noise levels. Reducing exposure to air pollution and second-hand tobacco smoke, preventing head injury (particularly by targeting high-risk occupations and transport), as well as preventing alcohol misuse and limiting drinking to less than 21 units per week, are other suggestions. “Stop smoking uptake and support individuals to stop smoking, provide all children with primary and secondary education, lead an active life into mid, and possibly later life, and reduce obesity and diabetes,” the authors emphasize.
Such actions are especially important in low-income and middle-income countries where dementia rates are rising more rapidly than in high-income countries, say experts. 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, hearing loss and rapidly growing rates of diabetes, they explain.
Based on their past model, including the nine risk factors, the authors estimated that many more cases of dementia could be prevented in LMICs, compared to globally. While globally the nine risk factors were estimated to contribute to 35% of all dementia cases, in China they might account for 40% of cases, 41% in India, and 56% in Latin America. The researchers, however, 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 the risks might differ for LMICs, and interventions might require modifying to best support different cultures and environments.
“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 prioritized. We also need more dementia research coming from low- and middle-income countries, so we can better understand the risks particular to these settings,” suggests co-author, Professor Adesola Ogunniyi, University of Ibadan, Nigeria.
The report advocates for “holistic and individualized 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 hospitalizations, it suggests. “Knowledge about risk factors and potential prevention, detection, and diagnosis of dementia is improving although significant gaps remain. Interventions, including organization of the complex physical illness and social needs, to support people affected by dementia can have a huge effect when taken as a whole,” say researchers.