The Lancet commission on “Dementia Prevention, Intervention, and Care” has identified essential measures that will reduce the risk of the disease.
In an article published last July in The Lancet, an expert commission has defined the main risk factors for dementia and has pointed out the most effective methods to prevent and treat this disease.
Dementia affects nearly 50 million people in the world (47 millions were estimated in 2015). As our longevity increases, this number is bound to triplicate by 2050 if we don’t take any preventive measure. Dementia generally occurs in people older than 65 years.
The key point, as stated by the expert panel, is that “dementia is by no means an inevitable consequence of reaching retirement age, or even of entering the ninth decade”.
In other words: dementia can be prevented.
Prevention requires reducing dementia risk factors during the whole course of life.
What is dementia?
There are different types of dementia, with distinct physical causes and biological features. The most common forms of the disease are: Alzheimer’s disease, vascular dementia, dementia with Lewy bodies, mixed dementia (with traits of more than one forms), dementia associated with brain traumas, infections, alcohol abuse.
The most common symptoms of dementia are: cognitive decline (memory loss, difficulties in speech and in critical thinking), frequent mood changes from depression to euphoria, agitation, psychosis (delusions, delirium, sometimes hallucinations), sleep disturbances.
Mild cognitive decline is not dementia.
Mild cognitive decline occurs in about one fifth of people older than 65 years. It is characterized by some memory impairment and decreased quickness of thought, but it allows people who are affected to go on with their normal activities, which will require just a bigger effort or some new strategies.
However, mild cognitive decline is a risk factor for dementia and, as such, it must be treated to prevent its progression.
Risk factors for dementia
The main risk factor for dementia is age, which, of course, is not modifiable. However, its power might be reduced by acting on other factors.
In other words, it might be possible to push further the age at which dementia occurs today – i.e. beyond 65 years – by mitigating other risk factors for the disease.
Genetic factors linked to some forms of dementia are not modifiable at present.
Modifiable risk factors for dementia prevention. Dementia prevention implies reducing its risk factors.
What risk factors can be modified?
The Lancet commission has identified 9 risk factors that, when present, significantly increase the possibility of dementia in old age. All these 9 risk factors can be targeted and reduced:
MODIFIABLE risk factors for dementia
|LESS EDUCATION (none or primary school only)||HYPERTENSION||HEARING LOSS|
It is possible to prevent dementia by modifying the above risk factors and, thus, by increasing the brain cognitive reserve.
Dementia prevention and cognitive reserve
The brain cognitive reserve is the functional capacity of the brain, i.e. the brain’s capacity to activate and regulate the neural circuits that mediate cognitive processes: memory, imagination, reasoning, and so on.
A large cognitive reserve increases the brain’s ability to perceive reality and adequately react to it: it endows the brain with a more diverse array of neural circuits that can be modulated and coordinated to carry out everyday tasks and to respond to challenges. A brain with a large cognitive reserve can better adapt to, and manage different situations: it is more resilient.
The brain cognitive reserve is modifiable because the brain is plastic: its cells (neurons) can form new connections (synapses) and establish new circuits that regulate our cognitive functions throughout life.
Cognitive reserve and the risk factors for dementia
By increasing our cognitive reserve, we reduce our risk of dementia in late life.
A resilient brain has more functional options: if one neural circuit gets damaged, it is able to activate alternative circuits that can efficiently substitute for the damaged one.
How to increase the cognitive reserve? The Lancet commission explains that it’s possible to increase the cognitive reserve by taking on behaviors that limit or reduce the 9 risk factors indicated above.
These behaviors should become habitual and thus constitute a lifestyle, that ideally should be adopted since childhood.
Possible preventive interventions
Education: school education, study, and reading increase the cognitive reserve because they stimulate critical thinking and thus brain plasticity. It should be protracted beyond school years. Education also means teaching healthy habits, from healthy nutrition to regular physical activity.
Hypertension, obesity, diabetes must be controlled because they may cause directly (hypertension) or indirectly (obesity and diabetes) vascular damage in the brain and thus compromise its function, with a reduction of the cognitive reserve.
Hearing loss: several scientific studies have shown that hearing loss since midlife is associated with increased risk for dementia. This is probably due to multiple causes, including changes in brain activity because of reduced sound stimuli, and difficulties in social interactions and consequently a tendency to social isolation and possibly depression. Hearing aids and initiatives that promote social interactions can help stabilize and improve the cognitive reserve.
Physical exercise: Various studies have observed that the practice of physical exercise is inversely related to the risk of dementia: more regular physical activity throughout life is associated with lower risk of dementia in old age. In addition, older people who regularly engage in physical exercise have a higher probability to maintain normal cognitive abilities than people who are physically inactive.
The importance of physical exercise in dementia prevention
A series of scientific studies has found that aerobic exercise (which improves the cardiorespiratory function) and resistance training (which increases muscle force and resistance) are the most beneficial to cognitive capacities: the former especially to memory, the latter to reasoning capacities. Also Tai Chi, a type of physical exercise that harmoniously combines slow movements with breathing, improves attention and processing speed.
Clearly, any exercise program must be adapted to age, physical conditions, and health status to be beneficial and improve the cognitive reserve.
But how does physical exercise reduce the risk of dementia?
Besides improving muscle tone and cardiovascular function, and reducing the risk of obesity and diabetes, regular physical activity exerts direct effects on the brain:
- it increases the blood flow to the brain
- it promotes the release of chemicals that protect brain neurons and stimulate neurogenesis and brain plasticity.
Physical exercise directly increases the cognitive reserve by remodeling the connections between neurons, and by improving the brain’s functional capacities.
In fact, a study in healthy adults, aged between 55 and 80 years, has demonstrated that walking for 40 minutes three times a week for a year increased the size of the hippocampus (a brain structure implicated in memory) and improved memory.
It is demonstrated that regular physical exercise is associated with better cognitive abilities and greater brain health; however, there is not enough scientific evidence yet that physical exercise protects against diseases (Alzheimer’s disease, dementia with Lewy bodies etc.) that cause dementia. Studies to clarify this point are ongoing.
Conclusions from the Lancet commission
Dementia can in large part be prevented.
A healthy lifestyle increases the brain’s cognitive reserve, its ability to adapt and react to different challenges, and to maintain its functional capacities.
Besides avoiding certain behaviors like unhealthy eating (that favors hypertension, obesity and diabetes) and smoking, the Lancet commission recommends taking on activities and adopting behaviors that stimulate the plasticity of the brain.
Among these activities, the most important and effective are:
- prolonged education (beyond school years and ideally throughout life)
- treatment of hearing problems
- regular practice of physical exercise
“Dementia prevention, intervention, and care”, G. Livingston et al., The Lancet (2017) http://dx.doi.org/10.1016/S0140-6736(17)31363-6