By Aideen Sullivan, University College Cork

Currently, there is much interest in the ageing brain and how people can take measures to counteract the decline in mental function that appears to be an inevitable consequence of growing older. The World Health Organization predicts that between 2015 and 2050, the proportion of the world’s population aged over 60 will nearly double, from 12% to 22%. So more people are living for longer, meaning that age-related disease and disability is a major and escalating concern for society.

The term ‘cognitive decline’ is often used to describe the deterioration in some aspects of brain function that occurs with age. Dementia is used to define a decline in mental ability that is severe enough to interfere with daily life. It is characterized by memory loss and by difficulties with thinking, problem-solving or communicating. There are several causes of dementia, with Alzheimer’s disease being the most common type, followed by vascular dementia.

The number of people living with dementia worldwide is currently estimated at 47.5 million and is projected to increase to over 130 million by 2050. Numerous studies have investigated factors that affect a person’s risk of developing dementia and age-related cognitive decline. A number of factors, outlined below, have been identified as having beneficial effects on mental function, particular in older adults.

Physical activity

There has been much interest in a link between an active lifestyle and a healthy brain. Epidemiological studies have found that people who lead a physically active lifestyle have a lower risk of cognitive decline with age. Older people who participate in moderate to vigorous exercise, especially aerobic exercise, show beneficial changes in brain structure and function, as well as in tests of memory and thinking skills. Although to date there is no clear-cut evidence for physical activity actually preventing age-related cognitive decline or the risk of developing dementia, there is a wealth of convincing data for exercise having positive effects on the brain. Exercise is known to improve cardiovascular function, and it may be that the beneficial effects on brain health are partly due to protection of blood vessels in the brain, damage to which can lead to risk of dementia as well as to stroke. Cerebrovascular diseases such as stroke are responsible for 85% of deaths due to neurological disorders, meaning that maintaining physically active throughout life can have a significant health impact.  You can read more about the impact of physical activity on the brain in a 2016 report published by the Global Council on Brain Health (GCBH).

Healthy diet

There is some evidence for protective effects of the ‘Mediterranean diet’ on brain health, as well as its well-documented benefits on cardiovascular health. The Mediterranean diet is characterized by high amounts of vegetables, fruit, cereals, and nuts, moderate intake of fish, dairy and red wine, and low intake of red and processed meat. Several prospective studies have found an association between a Mediterranean diet and slower cognitive decline with age, with a trend for a reduced risk for developing mild cognitive impairment and Alzheimer’s disease. Studies have also reported positive links between dietary omega-3 fatty acids, anti-oxidants, and Vitamins B and D on cognitive function. Lowering blood cholesterol levels and maintaining blood pressure within a normal range has been proven to reduce risk of stroke and vascular dementia.

Sleep

People who do not have adequate sleep over a long period of time are at higher risk of dementia and depression, as well as heart disease, diabetes and cancer. Our sleep patterns change with age, but the total amount of sleep needed for good physical and cognitive health does not decrease – most adults should sleep for 7 to 8 hours per night throughout their lives. However, sleep disorders increase with age, with corresponding effects on health. Many studies have shown negative links between sleep deprivation and attention, memory and executive brain function. Older adults who have poor sleep are more likely to feel depressed, have attention and memory problems, suffer from excessive daytime sleepiness and to experience more falls. In younger adults, the effects of sleep deprivation seem to be even more pronounced, highlighting the need for people of all ages to maintain good sleep habits throughout life. You can read more about the brain-sleep connection in a recent report by the GCBH.

Active social life

Strong social engagement has been shown to improve brain health. In 2016, the Global Council on Brain Health published an extensive review showing ample evidence to support the theory that older people who are more socially active and have larger social networks tend to have a higher level of cognitive function. The studies that they analyzed included one showing that volunteering led to improvements in memory, processing speed, and executive function. It is notable that the benefits were greatest when social engagement involved learning new skills rather than just spending more time with others or passively receiving information. For example, one study found that people who participated in quilting or digital photography in a social group showed greater improvements in memory and in speed of mental processing, compared to people who had engaged in activities that required little new learning (i.e. socializing or listening to classical music). The most recent report by the GCBH covers the link between brain health and social connectedness.

Mental activity

Mental challenges can improve brain function. Mental activity and learning are known to contribute to the establishment and maintenance of dense networks of connections between brain cells. Strategy-based cognitive training, for example tricks to remember lists of words, has been shown to help older people to improve their speed of reasoning – and the benefits of this training can last up to a decade. Challenging the brain by acquiring new skills (for example, learning a new language or mastering a musical instrument), or experiencing new situations and places, can help to build resilience against age-induced damage to neuronal networks. The inspirational Jewish-Italian neurobiologist Rita Levi-Montalcini said: “At 100, I have a mind that is superior – thanks to experience – than when I was 20.” She died at the age of 103, having continued working and publishing her research until 2012, the year of her death. Her work on nerve growth factor and its role in the developing nervous system, for which she was awarded the Nobel prize in Physiology or Medicine in 1986, leaves a legacy that has had a major impact on the understanding and therapy of Alzheimer’s and other brain diseases.

It is important to note that many of the studies described above are observational in nature, designed to find links between lifestyle activities over time with long-term results, in large numbers of people. There is a need for further hypothesis-based controlled studies to support these, in order to provide solid recommendations regarding lifestyle factors that can improve brain health. The WHO have committed to supporting a ‘Decade of Healthy Ageing’ from 2020 to 2030. Before 2020, there will be a large drive for researchers to collect and analyze data regarding factors that can affect Healthy Ageing, to allow the implementation of an evidence-based action plan that will give every person access to information that they can use to improve their prospects for a healthy older life.

Brain Awareness Week is an annual global campaign to enhance public awareness of brain research, and its benefits to society and the individual. This year, the 22nd annual Brain Awareness Week takes place from March 13-17, with events due to be held in over 40 countries.