40% of dementia cases could be prevented by targeting 12 risk factors
Modifying 12 risk factors over the lifecourse could delay or prevent 40% of dementia cases, according to 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).
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 mid-life, 1% of cases
to excessive alcohol consumption (of more than 21 units per week) in mid-life,
and 2% to exposure to air pollution in later life.
The remaining risk factors are associated with 34% of all dementia cases [1].
The factors associated with the greatest proportion of dementia cases in the
population are less education in early life, hearing loss in mid-life, and
smoking in later life (7%, 8%, and 5%, respectively).
Led by 28 world-leading dementia experts, the report builds on the 9 risk
factors identified in the 2017 Lancet Commission [2], 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. [3] Dementia affects individuals, their families, and the economy, with global costs estimated at about US$1 trillion annually.(3)
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.
Professor Livingston continues, "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." [4]
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% of all dementia cases, in China they might account for 40% of cases, 41% in India and 56% 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 dementiaand 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." [4]
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.