Dementia is a well-known syndrome (a group of related symptoms) related with an ongoing decline of brain functioning. It has many different causes, and there are many different types. Research shows over 850,000 individuals in the UK and around 50 million worldwide live with dementia, and the number of people with dementia is increasing because people are living longer. The number of older people, including those living with dementia, is on the increase, as younger age mortality declines. However, the age-specific incidence of dementia has fallen in many countries, most likely due to improvements in education, nutrition, healthcare, and lifestyle changes.
In 2017, The Lancet Commission released a report of their findings on Dementia Prevention, Intervention and Care. They found that 9 lifestyle factors were responsible for 35% of dementia burden, and these risk factors are less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, and low social contact. Overall, an increasing amount of evidence supports the 9 potentially modifiable risk factors for dementia modelled by the 2017 Lancet Commission on dementia prevention, intervention, and care.
The original 2017 Lancet Commission has recently been updated to identify the evidence for advances likely to have the greatest impact since the 2017 paper and build on its work. And as a result, 3 additional risk factors for dementia have been added with newer, convincing evidence. These factors are excessive alcohol consumption, traumatic brain injury, and air pollution. The researchers on the 2020 report 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 potential for prevention is high and might be higher in low-income and middle-income countries (LMIC) where more dementias occur. In LMIC, not everyone has access to secondary education, there are higher rates of hypertension, obesity, and hearing loss, and the prevalence of diabetes and smoking are growing, and so an even greater proportion of dementia is potentially preventable in LMIC.
From both the 2017 and 2020 reports, the mentioned specific actions for risk factors across the life course include:
- Aim to maintain systolic BP of 130 mm Hg or less in midlife from around age 40 years (antihypertensive treatment for hypertension is the only known effective preventive medication for dementia).
- Encourage use of hearing aids for hearing loss and reduce hearing loss by protection of ears from excessive noise exposure.
- Reduce exposure to air pollution and second-hand tobacco smoke.
- Prevent head injury.
- Limit alcohol use, as alcohol misuse and drinking more than 21 units weekly increase the risk of dementia.
- Avoid smoking uptake and support smoking cessation to stop smoking, as this reduces the risk of dementia even in later life.
- Provide all children with primary and secondary education.
- Reduce obesity and the linked condition of diabetes. Sustain midlife, and possibly later life physical activity.
- Encourage social, cognitive, and physical activity across the life course for all.
- Addressing other putative risk factors for dementia, like sleep, through lifestyle interventions, will improve general health.
Risk factors in early life (education), midlife (hypertension, obesity, hearing loss, traumatic brain injury, and alcohol misuse) and later life (smoking, depression, physical inactivity, social isolation, diabetes, and air pollution) can contribute to increased dementia risk. Good evidence exists for all these risk factors although some late-life factors, such as depression, possibly have a bidirectional impact and are also part of the prodrome and early stages of dementia.
This Commission is the most comprehensive analysis to date and gives a hopeful picture with an estimate of around 40% of all cases of dementia being associated with 12 potentially modifiable risk factors. Although a need for more evidence is apparent, recommendations should not wait, as clear indications of ways to reduce the chances of developing dementia without causing harm will also lead to other health and wellbeing benefits.
Original Source: Livingston G, Huntley J, Sommerlad A, Ames D, Ballard C, Banerjee S, et al. (2020) “Dementia prevention, intervention, and care: 2020 report of the Lancet Commission.” The Lancet.