There is plenty of evidence that physical activity is good for brain resilience and in later life can help stave off cognitive decline. In fact, it is estimated that regular exercise may reduce the risk of developing dementia by 30%.
What has been less clear is whether there is a particular point during adulthood when exercise is more crucial for brain health. Some research has suggested that being active in middle age is most beneficial for later-life cognition, but those studies often have short follow-up periods.
To better answer the question, Sarah-Naomi James, a neuro-epidemiologist at University College London, turned to the 1946 British Cohort Study. This longitudinal research involves participants born in England, Scotland and Wales during one week in March 1946. Originally, there were more than 5000 of them, but some have since died or dropped out of the project. So James was left with 1500 people who had reported their leisure-time physical activity at five stages of life – ages 36, 43, 53, 60-64 and 69 – and, at 69, completed a range of cognitive tests to assess attention, verbal fluency, memory, language, orientation and visual-spatial function.
The researchers found 11% of participants were sedentary at all five time points; 17% were active at one; 20% were active at two; 20% at three; 17% at four; and 15% remained physically active throughout.
“Our question was, is there a specific period of life where exercising is going to be more important? And the simple answer to that is, no, there is not,” says James. “Actually, the effects are very similar across every decade.”
The researchers found that by the time participants reached their 70s, those who were active at any stage at all had higher cognition than those who were sedentary throughout. It didn’t seem to matter how frequently they exercised or to what intensity.
However, what did make a significant difference was consistency. “The more decades that you’re active in, the higher your cognition,” says James.
Being active at all five time points was associated with the highest cognitive performance in later life.
There is positive news, however, for those who were sedentary in their earlier decades and have since made an effort to improve their fitness. Researchers did see brain health benefits for people who decided to start exercising in their 50s and 60s after a lifetime of inactivity.
“They had higher cognition than people who had never been active,” says James. “So, a key message is that it’s not too late. And we don’t all have to be marathon runners; just do something. Any activity at any point in life is good and for those who are already active, keep at it.”
Researchers are now looking in more depth at the different types of activity, although, says James, the one most people were engaging in in later life was, perhaps unsurprisingly, brisk walking.
“Another interesting piece of our research is looking at cognitive reserve. When some people reach their 70s, we can see from looking at their brains that they are starting to get the markers that are associated with dementia [amyloid plaques, tau tangles and changes to hippocampal volume] but they don’t necessarily show symptoms such as memory loss. We’re interested in looking back at the life course and asking what is it about these people that means these things happen earlier, and can we delay cognitive impairments?”
Using multimodal MRI and PET scans, researchers are able to examine levels of various proteins in the brain along with brain structure and blood vessel integrity, and then look at physical activity in relation to those measures of brain health.
If you do develop dementia, it can end up leading to inactivity as areas of the brain responsible for co-ordination and balance become affected. In the later stages, many people stop walking altogether. So, finding ways to keep them moving is another aspect of managing the disease.
“The message,” says James, “is not just to be active, but to be active for as long as possible.”
