According to the World Health Organization (WHO), there are 50 million people with dementia, with 10 million new cases each year. In July 2018, the WHO Guideline Development Group (GDG), which consisted of 21 clinicians and academic researchers from around the world, convened at the WHO headquarters in Geneva to evaluate and discuss the evidence for different dementia prevention strategies, their potential benefits and harm, along with their costs and practicality. Seven different lifestyle interventions were evaluated and their summaries were published in May 2019 [1]. Here, we discuss these summaries and their recommendations.
1. Physical activity
People who are physically active have reduced risks for cognitive decline, Alzheimer’s disease, vascular dementia, and other dementias. But how effective is physical activity as an intervention for brain health? The WHO GDG evaluated several systematic reviews that tested the effects of aerobic exercise, training exercise, and multimodal exercise interventions. Results from these studies suggest that physical activity has a small but beneficial effect on cognitive functions, and benefits are greater for aerobic training compared to resistance training [1]. Based on these findings, the WHO GDG strongly recommends physical activity to reduce the risk of cognitive decline.
Physical activity includes sports and planned exercises as well as walking, cycling, and household chores. For adults aged 65 years and above, the WHO recommends 150 minutes or more of moderate-intensity aerobic physical activity per week, or 75 minutes or more of vigorous-intensity aerobic physical activity per week (or an equivalent combination of moderate and vigorous activity).
2. Quitting tobacco smoking
Smoking cigarettes is associated with serious health risks, including many types of cancers, cardiovascular disease, asthma, and chronic obstructive pulmonary disease. Observational studies have shown that people who smoke are also at a higher risk of developing all types of dementia and up to a 79% increased risk for Alzheimer's disease, specifically [2]. The WHO GDG strongly recommends interventions for quitting tobacco use since they may reduce the risk of cognitive decline and dementia [1].
There are behavioral as well as drug interventions for quitting tobacco. Behavioral interventions include counselling, mindfulness-based approaches, cognitive behavioral therapy, contingency management, and others. Drug therapies include nicotine replacement therapy, bupropion, and varenicline. Combinations of both behavioral and pharmacological approaches have been reported to be the most effective [1].
3. Nutrition and diet
A healthy diet is important for maintaining overall health, but it is also important for brain health. There are observational studies suggesting that a healthy diet is associated with larger brain volumes and better cognitive performance. There are many different types of diets, but the Mediterranean diet has been the most extensively studied. Although the evidence from clinical trials is more limited and inconsistent, the WHO GDG strongly recommends a healthy balanced diet to all adults, and tentatively recommends a Mediterranean-like diet to reduce the risk of cognitive decline and dementia [1]. In contrast, the WHO GDG did not recommend taking supplements such as vitamin B, vitamin E, polyunsaturated fatty acids, and multi-complex vitamins, as no benefits were found with these supplements in people without nutrient deficiencies.
A healthy diet consists of fruits and vegetables (at least 400 g, or five portions per day), legumes, nuts and whole grains, with less than 10% of total caloric intake from free sugars, less than 30% of total caloric intake from fats, and less than 5 g of salt. The Mediterranean diet consists of high amounts of fruits, vegetables, potatoes, whole grains, fish, poultry, legumes, nuts, low-to-moderate alcohol, and monounsaturated fat (e.g., olive oil), while limiting red meat and full-fat dairy. You can learn more about the different diets and how they relate to brain health by reading our blog posts on the Mediterranean diet, DASH diet, MIND diet, vegetarian and vegan diets, and intermittent fasting.
4. Reducing alcohol use disorder
The evidence on the effects of alcohol on brain health has been inconsistent, with some studies suggesting that low-to-moderate alcohol intake is beneficial for brain health, while other studies suggesting that even light drinking can be harmful. However, the evidence is more consistent when it comes to excessive alcohol consumption, which is a significant risk factor for dementia and cognitive decline [1;3]. The WHO GDG recommends interventions to stop harmful drinking in order to reduce the risk of cognitive decline and dementia.
Interventions for alcohol use disorder include behavioral/psychological therapies and drug treatments [1]. Behavior/psychological therapies include cognitive behavior therapy, motivational enhancement therapy, family counselling/therapy, self-help groups, and others, and are typically more acceptable and have few side effects. Drug interventions include medications that treat withdrawal symptoms or prevent relapse, but a range of adverse events have been reported for some of these treatments.
5. Cognitive interventions
Lifelong learning is associated with cognitive health, and higher levels of cognitive activity at mid- or late-life are linked to delayed onset of cognitive impairment [4]. The WHO GDG evaluated two types of cognitive interventions: cognitive stimulation which consists of a range of activities aimed at improving cognitive and social functions, and cognitive training which refers to the practice of specific tasks designed to improve particular cognitive functions [5]. Based on the limited but positive evidence, the WHO GDG tentatively recommended cognitive training for reducing the risk of dementia. However, no recommendation was made for cognitive stimulation, which had insufficient evidence.
At Cognitive Vitality, we previously discussed a large 10-year clinical trial that tested the effects of different cognitive training programs in 2,832 healthy older adults [5]. Researchers found that a specific type of brain training called speed-of-processing lowered dementia risk by up to 29%. As exciting as these findings were, the results will need to be confirmed in other studies to be certain that these benefits are consistent.
6. Social activity
Social isolation is a risk factor not only for dementia but also for hypertension, coronary heart disease, and depression [6]. Low social participation, fewer social contacts, and more loneliness have all been associated with increased dementia risk [7]. The WHO GDG evaluated three randomized controlled trials that assessed the association between social activity and cognitive function, and one of the three found that a social activity intervention improved cognitive functions [1]. Based on the limited and inconclusive evidence, the WHO GDG did not make a specific recommendation for social activity to reduce the risk of cognitive decline and dementia. But they noted that social participation and social support are strongly connected to overall health and well-being and should be encouraged throughout life.
7. Weight management
Observational studies have reported that people who are obese in midlife have an increased risk of dementia compared to those with healthy body weight [8]. Being overweight or obese is also linked to several medical conditions, including type 2 diabetes, cancer, and cardiovascular disease [1]. Based on a systematic review suggesting that lifestyle interventions aimed at weight loss could improve some cognitive functions, such as attention, memory, and language [9], the WHO GDG made a conditional recommendation for weight management interventions in middle-aged adults (but not for elderly people) [1].
The WHO recommendations for people who are overweight and obese include the following: 1) eat a healthy balanced diet, 2) eat low glycemic-index foods (beans, lentils, oats, and unsweetened fruit) as their source of carbohydrates, and 3) reduce sedentary behavior while increasing physical activity [1]. Lifestyle interventions that include both diet and physical activity have been reported to produce the best results.
The WHO guidelines are good news in that there are steps you can take to reduce your risk for cognitive decline and dementia. These recommendations are very much in line with our seven steps for brain health.
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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