The well-documented health benefits conferred by aerobic activities such as running tend to emphasise cardiovascular improvements, such as reduced blood pressure, and the fact that aerobic exercise can even improve the course of many chronic diseases. However, relatively little attention has been given to the positive effects exerted by running on brain health and cognitive function.
If we consider brain cancer, for example, according to the National Cancer Registry Ireland, about 290 malignant primary brain tumours are diagnosed annually in Ireland, accounting for just under 2 per cent of all invasive cancers. Brain tumours are more commonly diagnosed in men than women, with a median age at diagnosis of 60 years.
But the title of a Californian study published in 2014 in the journal Medicine & Science in Sports & Exercise is unambiguous. In "Reduced Risk of Brain Cancer Mortality from Walking and Running", Dr Paul T Williams describes how over 150,000 individuals were followed up for 12 years, and details of exercise, health problems, diet and lifestyle recorded. Exercise was measured in metabolic equivalent hours per day of exercise (MET-hours/d), with 1 MET-hour/d equal to a one-kilometre run.
Williams found that the risk for brain cancer mortality was 43.2 per cent lower for those who ran or walked 1.8 to 3.6 MET-hours/d, which equates to 12-25 km running or 19-37km brisk walking per week.
This may be partly linked to proteins. Laboratory studies suggest that over-expression of a protein called insulin-like growth factor (IGF-1) in the adult brain may be a risk factor for tumour development, and it is known that short-term endurance exercise decreases the concentration of IGF-1.
Another aspect researchers are focusing on is dementia. The Alzheimer’s Society of Ireland note that there are 55,000 people in Ireland living with dementia, and worldwide it is anticipated that in the absence of effective treatment and prevention the prevalence of Alzheimer’s disease (AD) will triple by 2050.
But there is some encouraging news. Last year, researchers from the University of Texas Southwestern Medical Center, in a major review published in Exercise and Sports Science Reviews, highlighted studies showing that about "30 per cent of AD cases may be related to modifiable risk factors such as physical inactivity and cardiovascular risk factors."
The article, entitled “The role of exercise-induced cardiovascular adaptation in brain health”, pointed to compelling evidence suggesting that habitual aerobic exercise helps reduce age-related cognitive decline by helping to preserve brain structure.
In one study cited by the researchers, master athletes (MA) were compared with sedentary individuals who were matched for age, sex, educational level, nutrition, sleep and other lifestyle factors. The study found that MAs displayed higher cognitive performance in memory and executive function.
So how could aerobic exercise help arrest age-related cognitive decline? There are some 100 billion nerve cells – neurons – in the brain. Axons are long, slender projections of neurons that conduct electrical impulses. These axons are surrounded by a sheath of myelin, and with advancing age the myelin becomes increasingly damaged, slowing the transmission of electric impulses. It seems that habitual aerobic exercise helps to attenuate this demyelination process, contributing to improvements in cognitive performance.
Regular aerobic exercise could also help increase or preserve brain volume in those regions affected by age and associated with impaired cognition. For example, one study of MAs and older adults with a sedentary lifestyle found that the brains of MAs had greater volumes in areas connected with motor control and visual/spatial function – one can infer that the demands of a running action which require muscular control, balance and spatial awareness would promote consolidation of those areas of the brain associated with controlling those attributes.
In the light of these and other published findings, some may be tempted to assume that the more strenuously you exercise, the better for your health. This is not the case. Emerging evidence suggests that if, for example, prolonged strenuous endurance exercise is undertaken without adequate recovery the brain could be adversely affected. Explanations for this remain unclear but it could be connected to a rise in metabolic breakdown products that occur, along with inflammatory responses.
Curbing screen time
For parents concerned about adverse effects of, for example, the screen-based preoccupations of their youngsters, a recent review in the Scandinavian Journal of Medicine & Science in Sports suggests that more time exercising and less time surfing will improve schoolwork.
The authors considered 45 studies published between 1990 and June 2016 that investigated the link between physical fitness (PF) and academic performance (AP). Of these studies, 25 “report a positive association between components of PF with AP and 20 describe a single association between cardiorespiratory fitness and AP”.
The authors conclude: “Both PF and motor skill may promote positive and sustainable trajectories of health, cognition, and AP leading to long-term positive health outcomes.”
It is clear that aerobic exercise is good for both developing and ageing bodies and minds.
Sign up for one of The Irish Times' Get Running programmes (it is free!).
First, pick the programme that suits you.
- Beginner Course: This programme is an eight-week course that will take you from inactivity to being able to run 30 minutes non-stop.
- Stay On Track: The second programme is an eight-week course for those of you who can squeeze in a 30- to 40-minute run three times a week.
- 10km Course: This is an eight-week course designed for those who can comfortably run for 30 minutes and want to move up to the 10km mark.
Best of luck!