In a recent study that reviewed factors linked to dementia, researchers estimated that 35% could be attributed to potentially controllable risk factors. Rates of dementia have fallen by up to 20% in high-income countries such as the United States, United Kingdom, and Canada, over the past twenty years. The theory is that this decline is related to changes in lifestyles of people in these higher-income countries, especially in diet.
A 2013 study in Spain found that people between the ages of 55 and 80 at high risk of developing cardiovascular disease who followed a Mediterranean diet scored better on cognitive tests six years later than those who merely followed a low-fat diet. Two more recent studies showed that the brains of healthy, middle-aged people who faithfully followed a Mediterranean diet showed less atrophy on magnetic resonance imaging scans and accumulated less of the protein amyloid-β that is associated with Alzheimer’s disease than did people who did not follow that diet. There are also well-established correlations between Alzheimer’s disease and conditions such as high blood pressure, high cholesterol, obesity, and type 2 diabetes, all of which can be impacted by what we eat.
Other research shows that physical activity can provide a buffer against cognitive decline. Exercise has an array of robust effects on the brain, such as enhanced memory, mood, cognitive functioning, plasticity, and learning capabilities. New neurons can be generated in the adult brain via a process known as neurogenesis, and this phenomenon has been linked to exercise. The generation of new neurons and increased plasticity in the hippocampus (an area critical for memory) may explain the improved cognition that accompanies exercise. A key molecule mediating this process is brain-derived neurotrophic factor (BDNF), which helps with the survival of the new brain cells. Barnes found that older adults who exercised three or more times per week were more likely to remain dementia free during a 6-year follow-up period, independent of other risk factors for dementia.
According to U.S. Census data, 30% of Americans older than 65 live alone and half of those are age 85 or older. Research studies have shown that loneliness in itself is a risk factor for accelerated cognitive decline in older adults and that lonely people are at a 26 – 64 % higher risk of dementia. Holt-Lunstad found that lack of social connection heightens health risks as much as smoking 15 cigarettes a day or having alcohol use disorder, and surpasses the health risks associated with obesity.
Higher levels of education have also been linked with less risk of cognitive decline; each year of schooling beyond primary school appeared to increase the benefit. Advances in education, together with improvements in health care and living conditions, could explain why rates of dementia have fallen in high-income countries in the past two decades.
Being able to hear helps to keep the brain active and makes it less likely a person will socially isolate due to not being able to hear conversations. A recent observational study found that people who wore hearing aids did not show the same elevated risk of dementia as did people with untreated hearing problems. Lin and colleagues found that cognitive abilities (including memory and concentration) declined faster in older adults with hearing loss, as compared to older adults with normal hearing.
Ngandu and her colleagues have been analyzing data from the Finnish Geriatric Intervention Study to Prevent Cognitive Impairment and Disability (FINGER). In this study, more than 1,200 adults in Finland ages 60 to 77 who had a higher risk of dementia were randomly assigned to either a group that received coaching on diet, exercise, cognitive training and cardiovascular risk management, or to a control group that received only general advice on health. The researchers reported that after two years, though people in both groups showed cognitive improvements, the group that received coaching demonstrated a 25% greater improvement in memory, mental-processing speed and executive function.
Isaacson and his colleagues observed that after just six months on a personalized preventive plan, participants showed improvements in executive function and mental-processing speed. Isaacson believes that, though most lifestyle recommendations for brain health, such as eating a Mediterranean diet, can apply to all people, many could benefit more from a personalized plan of interventions. These plans could include aggressive treatment for cardiovascular conditions, medication for sleep apnea, or participation in specific types of physical activity.
To summarize, we can keep the brain healthy not only by exercising and eating well, but also by maintaining a robust social network, correcting problems with hearing, and getting regular intellectual stimulation through puzzles and other means. These activities, which spur the development of new neurons and neural connections, better enable the brain to compensate for losses in cognitive capacity that would otherwise affect daily living.