Dementia is a growing problem and a ticking time bomb for much of the world. As the average age of the global population grows, so too will the proportion of people living with dementia, as will the number of people and resources required to care for them. Dementias are also a very unpleasant and difficult set of conditions to deal with, both for the sufferer and for their loved ones. Fortunately, an individual person’s risk of dementia seems to be very modifiable. Studies suggest that at least 40% of dementia cases in the US could be prevented through lifestyle modifications.
There’s still much more research to be done to figure out which of those modifications are most important and how they exert their benefits. Some modifications appear to be more or less important depending on the age at which they’re made, for example.
But for now, here are the practices we think are the most important for delaying and preventing dementia onset, in approximate order of increasing importance. Don’t put too much stock in the order, though, as the impact of each factor has been shown to vary quite a lot depending on the population being studied.
Maintaining good oral hygiene could be important for preventing dementia. Research suggests that people with gum disease and mouth infections were more likely to develop Alzheimer’s disease. While this link might seem surprising at first, it has several plausible explanations. Pathogenic bacteria in the mouth could enter the bloodstream and cause inflammation, which is thought to drive neurodegenerative disease. There is also evidence that some pathogenic bacteria produce toxins that can encourage the accumulation of misfolded proteins in the brain.
Traumatic brain injuries are thought to be responsible for about 3% of dementia cases worldwide. However, evidence suggests that it takes less than a severe head injury to increase your risk of dementia. Repetitive blows to the head, even if they don’t cause injury, seem to be associated with increased risk of neurodegenerative disease.
Poor education appears to be one of the most important predictors of dementia, accounting for an estimated 7% of cases globally. Unfortunately, many people don’t have that much control over their level of education. However, there is evidence that continuing to learn and engage in cognitively demanding activities throughout life can reduce dementia risk. Building new connections within the brain seems to create a ‘cognitive reserve’, which blunts the impact of any pathology that occurs later in life.
Studies have consistently found that people who are more socially active are less likely to suffer from dementia. It is not entirely clear why this is, but it probably has more to do with cognitive and emotional benefits of a social circle, as opposed to any intrinsic benefits of social activity. Many social activities, even casual conversation, are more cognitively engaging than we might give them credit for, and will at the very least engage parts of the brain associated with language and facial recognition, for example.
While not easily modified, it would be remiss not to mention the relationship between depression and dementia risk. An estimated 4% of dementia globally is related to depression, so there are reasonable grounds to believe that seeking help for depression (and generally following lifestyle practices that promote good mental health) could reduce dementia risk in later life.
There is a strong association between sleep and dementia, and it is likely to be a two-way relationship, with poor sleep increasing dementia risk while dementia impairs sleep. This makes it hard to know what proportion of dementia cases could be attributable to poor sleep. We do know that good quality sleep is very important for learning, memory and cognitive performance during the day. Poor sleep also seems to increase your risk of other risk factors for dementia, such as high blood pressure and diabetes. Overall, the evidence is quite convincing that good sleep is necessary for a healthy brain.
Smoking is responsible for about 5% of dementia cases worldwide. Much of the increased risk from smoking seems to be due to damage and tightening of the blood vessels, restricting blood flow to the brain. Smoking also leads to increased levels of brain inflammation. The good news is that people who quit smoking seem to reduce their risk to a level similar to those who have never smoked at all.
Obesity has been estimated to increase risk of dementia by around 40%. Though it only accounts for around 1% of dementia globally, obesity may be responsible for around 7% of dementia cases in the United States (this is independent of other dementia risk factors linked to obesity, such as lack of exercise and high blood pressure).
According to large meta-analyses, sedentary behaviour increases risk of dementia by about 30%. Studies suggest that lack of exercise is linked to about 2% of dementia cases globally, and about 7% in the United States. Evidence also suggests that you don’t need to exercise very much to reduce your risk of dementia significantly, even when you are older. One study found that a mere 20 minutes of walking per day reduced dementia risk by 14% in people over the age of 65.
It may come as a surprise to learn that the biggest contributor to dementia cases globally is poor hearing. According to a Lancet report, hearing loss is responsible for an estimated 8% of dementia cases globally. This relationship is still being studied, but it seems that the activity of pathways in the brain involved in hearing may be particularly important for preserving cognitive function. There is even some evidence that treating hearing loss with hearing aids may prevent dementia, but more work needs to be done.
Title image by Robina Weermeijer, Upslash
Clinical and Bacterial Markers of Periodontitis and Their Association with Incident All-Cause and Alzheimer's Disease Dementia in a Large National Survey: https://doi.org/10.3233/jad-200064
Lancet Commission’s Dementia Hit List Adds Alcohol, Pollution, TBI: https://www.alzforum.org/news/conference-coverage/lancet-commissions-dementia-hit-list-adds-alcohol-pollution-tbi
Smokers Have a Higher Risk of Developing Dementia: https://www.healthline.com/health-news/smoking-and-dementia
Obesity Can Increase Dementia Risk By Up To 80 Percent, Study Suggests: https://www.sciencedaily.com/releases/2008/05/080507105556.htm
Association between sedentary behavior and the risk of dementia: a systematic review and meta-analysis: https://doi.org/10.1038/s41398-020-0799-5
How Exercise May Lower Your Risk of Dementia: https://www.pihhealth.org/wellness/articles/dementia-risk-exercise/
How Can Hearing Loss Cause Dementia?: https://doi.org/10.1016%2Fj.neuron.2020.08.003