We previously discussed findings from the 2020 Lancet Commission on Dementia Prevention, Intervention and Care, suggesting that fully addressing 12 lifestyle risk factors may prevent up to 40% of dementia cases. In July 2024, the Lancet Commission added two new risk factors and reported that 45% of dementia cases could be prevented by fully addressing 14 lifestyle factors [1]. The risk factors worth addressing vary by life stage: early life (under 18 years old), midlife (18 to 65 years old), and late life (over 65 years old).
Not completing secondary education Not attending secondary school increases your risk of dementia [1; 2]. Low educational attainment can make people more vulnerable to cognitive decline, because it results in less “cognitive reserve”, a reserve that helps maintain cognitive function despite brain aging and even pathology in some cases. In contrast, lifelong learning is associated with improved brain health, and higher levels of cognitive activity at mid- or late-life are linked to delayed onset of cognitive impairment [3]. Even in people with less education, cognitive stimulation at work is associated with lower dementia risk [4].
Hearing loss Many high-quality observational studies suggest an association between hearing loss and subsequent dementia [1]. Studies have found that with every 10-dB decrease in hearing ability, there is a 4 to 24% higher risk of dementia [5; 6]. It is possible that hearing loss promotes the development of dementia, or the changes dementia produces in the brain impairs hearing function, or both. Hearing loss may also lead to social isolation or depression, both of which are also associated with dementia risk (see below). The good news is hearing loss may be corrected with the use of hearing aids. A recent analysis of four studies reported that people with hearing loss who used hearing aids had a significantly lower risk of cognitive decline and dementia [7].
High LDL cholesterol At the time of the previous Lancet Commission on dementia published in 2020, the evidence related to LDL cholesterol was inconclusive [8]. Since then, studies have reported that high LDL cholesterol in midlife is associated with a higher risk of dementia [1; 9]. Excess brain cholesterol is associated with increased risk of stroke and deposition of Alzheimer’s disease-related pathology (i.e., amyloid and tau). In contrast, people who took lipid-lowering drugs did not have an increased risk of dementia, emphasizing the importance of treating high LDL cholesterol, not just for cardiovascular health, but also for brain health.
Depression People with depression have a higher risk of dementia than those without depression. Depression at all adult ages is associated with higher dementia risk, but the evidence is most clear for midlife depression [1]. Depression may heighten dementia risk by increasing stress hormones, decreasing levels of proteins that are good for brain cells, and shrinking the hippocampus, a brain region critical for forming memory [10; 11]. People who were treated for depression by medication, psychotherapy, or combination therapy were less likely to develop dementia than people with depression who received no treatment [12], highlighting the importance of treating depression.
Traumatic brain injury Traumatic brain injury is caused by car/motorcycle/bicycle accidents, military incidents, boxing, other contact sports, and falls. Studies suggest that traumatic brain injury is associated with a higher dementia risk, possibly leading to earlier onset of dementia by two to three years than in people without traumatic brain injury [13]. 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 [14]. It is also important to maintain a safe environment to prevent falls.
Physical inactivity Being physically active at all ages is associated with better cognition and lower dementia risk [1; 15]. There are many ways that physical activity might benefit brain health. It reduces chronic inflammation, improves blood flow, increases the release of a protein that is very good for brain cells [16], and improves cardiovascular and metabolic health [17; 18]. The World Health Organization recommends that adults get 150 to 300 minutes of moderate-intensity aerobic physical activity (or 75 to 150 minutes of vigorous-intensity physical activity) every week, along with at least two days a week of muscle-strengthening activities [19].
Diabetes In the previous Lancet Commission on dementia in 2020, type 2 diabetes in late life was associated with a higher risk of dementia [8]. Newer evidence suggests that the age of onset makes a difference, with a midlife onset of type 2 diabetes being significantly associated with higher dementia risk, while late-life onset is not [1]. It is possible that the longer duration of illness and poorly controlled diabetes may increase the risk of dementia. Type 2 diabetes and dementia share some characteristics, such as impaired insulin signaling, altered brain metabolism, vascular complications, inflammation, and oxidative stress [20]. A healthy diet, exercise, and weight control are the first steps of diabetes management, followed by medication(s).
Smoking Cigarettes and cigarette smoke contain more than 4,700 chemical compounds, including some that are highly toxic [21]. Observational studies have shown that people who smoke are at a higher risk of developing all types of dementia and a much higher risk (up to 79%) for Alzheimer's disease, specifically [22]. New evidence suggests that midlife smoking appears to be a stronger risk factor for dementia than smoking in late life [1]. The good news is that quitting can reduce your risk of dementia, as some studies report no increased risk in former smokers [23; 24].
Hypertension Studies suggest that having hypertension (high blood pressure) in midlife increases the risk of both vascular dementia and Alzheimer's disease [1; 26]. The evidence is mixed in late-life as some people who develop dementia have lower blood pressure than people without dementia [1]. Several analyses of multiple clinical trials found that people who received blood pressure medication had a lower risk of dementia and higher cognitive function than those receiving placebo [27; 28]. Hypertension can be managed through diet, lifestyle changes, and medications.
Obesity People who are obese in midlife have an increased risk of dementia compared to those with healthy body weight [29]. In an analysis that included a total of over five million people across 16 studies, higher central obesity, measured by waist circumference or waist-to-hip ratio, was associated with a greater risk of cognitive impairment and dementia [30]. Obesity is more common in people who do not get enough physical activity and is associated with increased risk for diabetes and hypertension, all of which are linked with increased dementia risk (see above). A study in people with mild cognitive impairment reported that normal body mass index (BMI under 25), greater physical activity, and healthier diet were associated with lower levels of plaques and tangles, which are markers of Alzheimer’s disease [31].
Excessive alcohol consumption Heavy drinking is associated with cognitive impairment and dementia [1]. The definition of heavy drinking varies across studies, but often refers to more than 21 units of alcohol per week (1 unit = 8 grams of pure alcohol; a single serving of wine or beer can have up to 3 units). 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 [32]. An analysis of 28 systematic reviews concluded that heavy alcohol use was associated with a higher risk of dementia and changes in brain structures [33].
Social isolation Social isolation is a risk factor not only for dementia but also for hypertension, coronary heart disease, and depression [2]. Low social participation, fewer social contacts, and more loneliness have all been associated with higher dementia risk [34]. Social isolation may result in decreased cognitive activity, which may accelerate cognitive decline and poor mood. Social contact in any form may reduce dementia risk by increasing cognitive reserve, brain volume, and healthy behaviors, and reducing stress and inflammation [35].
Air pollution Many studies show that air pollution, often measured by PM2.5 (fine ambient particulate matters with diameters less than 2.5 microns) and PM10 (particles with diameters less than 10 microns), is a risk factor for dementia and cognitive impairment [1; 36; 37]. Although air pollution cannot be entirely avoided, there are steps you can take to reduce your exposure, such as monitoring 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.
Untreated visual loss At the time of the previous Lancet Commission on dementia in 2020, vision loss was not considered as a risk factor for dementia [8]. However, new evidence has emerged since then. An analysis of numerous cohort studies reported that vision impairment is associated with a higher risk of both dementia and cognitive impairment [38]. These associations might be related to underlying illness, such as diabetes, which is a risk factor for both dementia and vision loss. A longitudinal cohort study in the US reported that people with cataract who had cataract extraction had a significantly lower dementia risk compared to those who did not have cataract extraction [39], highlighting the importance of treating vision impairment.
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The Lancet report is great news in that there are concrete steps you can take to reduce dementia risk. Invest in lifelong learning and friendships, get enough physical activity, wear a seatbelt in motor vehicles (and proper head protection in contact sports), maintain a healthy weight, quit smoking, avoid excessive alcohol intake, and seek treatment for depression, hypertension, high LDL cholesterol, diabetes, hearing loss, and vision loss if you have these conditions. These recommendations are consistent with evidence from a seminal randomized controlled trial called FINGER that showed a group of lifestyle interventions that addressed many of these risk factors improved cognitive function in older people [40].
References:
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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