We previously discussed findings from the 2017 Lancet Commission on Dementia Prevention, Intervention and Care, which reported that 35% of dementia cases could be prevented by fully addressing nine lifestyle risk factors [1]. This year, the Lancet Commission added three new risk factors based on newer convincing evidence: traumatic brain injury, air pollution, and excessive alcohol consumption [2]. Together, fully addressing all 12 risk factors is thought to prevent or delay up to 40% of dementia cases.
*In parentheses are the percent of dementia cases that could be prevented by eliminating the risk factor.
Traumatic brain injury is caused by car/motorcycle/bicycle accidents, military incidents, boxing, other contact sports, and falls. A single severe incident of traumatic brain injury has resulted in the emergence of a pathological marker of Alzheimer’s disease called “hyperphosphorylated tau” [3]. In two large observational studies that included millions of people each, traumatic brain injury was associated with an increased risk for dementia and increased risk for Alzheimer’s disease specifically [4; 5]. A single mild traumatic brain injury increased dementia risk less than a severe incident, while multiple traumatic brain injuries increased dementia risk more [5].
To prevent traumatic brain injury, the Centers for Disease Control and Prevention recommend wearing a seat belt every time you are in a motor vehicle; wear a helmet or appropriate headgear when riding bikes, motorcycles, snowmobiles, horses, or skateboards, as well as when you skate, ski, snowboard, or play contact sports [6]. It is also important to maintain a safe environment to prevent falls.
Air pollution is associated with poor health, including lung cancer, respiratory illness, heart disease, and stroke [7]. We have also discussed in our blog how air pollution could contribute to the risk of dementia, suggesting that air pollutants cause damage consistent with Alzheimer’s disease and other dementias in controlled laboratory experiments. A review that compiled findings from 13 longitudinal studies has found that high exposure to nitrogen dioxide, carbon monoxide, and fine ambient particulate matters with diameters less than 2.5 microns, called PM2.5, were all associated with increased dementia risk [8]. Carbon monoxide and PM2.5 are formed when fuel is burned in motor vehicles, stoves, grills, fireplaces, and furnaces. Nitrogen dioxide is produced from burning of fossil fuels and traffic exhaust.
Although air pollution cannot be entirely avoided, there are many steps you can take to reduce your exposure. For example, you can monitor air pollution levels online or with apps and stay indoors on days with particularly high air pollution. You can also limit exposure to car exhaust by closing vents and windows while in heavy traffic. For other tips to reduce your exposure to air pollution, see our blog post on air pollution.
Heavy drinking is associated with cognitive impairment and dementia. In a longitudinal study that included over 31 million people hospitalized in France, alcohol use disorders (i.e., harmful use or dependence) were associated with a greater than 3-fold increased risk of dementia—and the increased risk was especially pronounced for earlier onset dementias with onsets before 65 years of age [9].
The 2020 Lancet Commission report recommends avoiding alcohol misuse or drinking more than 21 units of alcohol per week. The good news is, although the evidence is inconsistent and mixed, we have previously rated low-to-moderate alcohol intake (one drink a day for women, two for men) as having potential benefit for brain health. Consistent with our rating, a review that compiled 45 observational studies reported that light to moderate drinking was associated with a 30% reduced risk of dementia compared with not drinking at all [10].
Below is a list of all 12 modifiable risk factors including the nine from the 2017 Lancet Commission report, which when fully addressed may delay or prevent dementia cases by up to 40%. Again, the percentages in parentheses represent the percent of dementia cases that could be prevented by eliminating the risk factor.
While concerning that there are increasing numbers of risk factors, the 2020 Lancet Commission update is good news in that there are concrete steps you can take to reduce dementia risk or delay its onset.
Yuko Hara, PhD, is Director of Aging and Alzheimer's Prevention at the Alzheimer's Drug Discovery Foundation. Dr. Hara was previously an Assistant Professor in Neuroscience at the Icahn School of Medicine at Mount Sinai, where she remains an adjunct faculty member. Her research focused on brain aging, specifically how estrogens and reproductive aging influence the aging brain's synapses and mitochondria. She earned a doctorate in neurology and neuroscience at Weill Graduate School of Medical Sciences of Cornell University and a bachelor's degree in biology from Cornell University, with additional study at Keio University in Japan. Dr. Hara has authored numerous peer-reviewed publications, including articles in PNAS and Journal of Neuroscience.
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