Last month, the Lancet Commission on Dementia Prevention, Intervention, and Care reported that 35% of dementia cases could be prevented by fully addressing nine lifestyle factors [1].
The risk factors follow, in order of the percent of dementia cases that could be prevented by eliminating them.
Studies have suggested that even mild levels of hearing loss may increase the long-term risk of cognitive decline and dementia [1]. An analysis across three studies showed that hearing loss in midlife is associated with an almost two-fold increased risk for dementia [2][3][4]. 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). Hearing loss may be corrected with the use of hearing aids.
Not attending secondary school also increases your risk of dementia [1]. Low educational levels can make you more vulnerable to cognitive decline, because it results in less "cognitive reserve" that allows you to maintain cognitive function despite brain aging and even beta-amyloid plaques 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 [5].
Cigarettes and cigarette smoke contain more than 4,700 chemical compounds, including some that are highly toxic [6]. Observational studies have shown that people who smoke are at higher risk of developing all types of dementia and a much higher risk (up to 79%) for Alzheimer's disease, specifically [7]. The good news is that quitting can reduce your risk of dementia, because current smokers have a higher risk than former smokers [7][8].
Research indicates that depressive episodes are linked to higher dementia risk—and this association appears most prominent in late-life [9][10]. 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 [11][12]. There are preliminary studies suggesting that some antidepressants may decrease markers of Alzheimer's disease [13].
Exercisers are less likely to develop dementia, particularly Alzheimer's disease [14][15]. There are many ways that exercise might benefit brain health. It reduces chronic inflammation, 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 at least 150 minutes of moderate-intensity (or 75 minutes of vigorous-intensity) aerobic exercise every week, along with at least two days of muscle-strengthening activities [19].
Social isolation is a risk factor not only for dementia but also for hypertension, coronary heart disease, and depression [1]. Low social participation, fewer social contacts, and more loneliness have all been associated with increased dementia risk [20]. Social isolation may result in decreased cognitive activity, which may accelerate cognitive decline and poor mood. It is recommended that you maintain social contacts throughout life and participate in engaging group activities.
Studies suggest that having hypertension in middle age increases the risk of both vascular dementia and Alzheimer's disease [21][22]. Even in later years, keeping hypertension under control may protect against cognitive decline [23]. An analysis of several studies found that people who managed their hypertension had a lower risk of dementia and higher cognitive function overall than those with uncontrolled hypertension [24]. Hypertension can be managed through diet, lifestyle changes, and medications.
Epidemiological studies have reported that people who are obese in midlife have an increased risk of dementia compared to those with healthy body weight [25]. Obesity increases risk for diabetes and hypertension, both of which are associated with increased risk of dementia (see above and below). 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 [26].
People with diabetes have up to 73% increased risk of dementia and a 100% higher risk of developing vascular dementia than non-diabetics [27-30]. Type 2 diabetes and Alzheimer’s disease share some characteristics, such as impaired insulin signaling and oxidative stress [31]. Because of this, research is underway to evaluate whether some specific diabetes drugs can prevent dementia even in patients without diabetes [32-35]. A healthy diet, exercise, and weight control are the first steps of diabetes management, and effectively managing diabetes is critical for long-term brain health.
The Lancet report is good news. There are concrete steps you can take to reduce dementia risk, such as investing in lifelong learning and friendships, exercising, maintaining a healthy weight, quitting smoking, and seeking treatment for depression, hypertension, diabetes, and hearing loss if you have these conditions.
BBC World News interviewed Howard Fillit, MD, the Founding Executive Director of Alzheimer's Drug Discovery Foundation, about the Lancet report findings.
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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