Stimuli on the go

When we are actively on the go, the world around us seems to move. Our brain perceives a continuous stream of new stimuli, in short: moving images stimulate your eyes and retina. They transmit this information via the optic nerves to our visual cortex and other brain areas that are involved in processing images. You also feel movement, information about balance and body position is combined with that visual information. Ultimately,all these brain areas work together to create a logical image and interpretation of the environment. This constant stream of visual information is also called 'optic flow'. Being on the go has even more advantages for the brain, because it also appeals to the spatial orientation ability, it requires attention and requires navigation skills.

The research group examined the data of 479,723 middle-aged adults. The average age of this group was 56.5 years old and slightly more than half were women. Data from these people was collected for 13 years and their data was entered into a large medical database. Of that group, 1.8% (8,845 people) were diagnosed with dementia and 0.8% (3,956 people) with Alzheimer's disease during the data collection.

Study participants reported how they had been exposed to moving images during the last 4 weeks by walking or cycling (travelling to and from work was not included) and 4 categories were determined:

• Inactive (by car or public transport)
• Walking only
• Mixed walking
• Cycling (mixed and only)

Data from hospitals and death registers were also collected. Brain structure was measured with an MRI scan. A statistical model was then used to determine the risk of dementia.

Benefits of moving images

Compared to the 'inactive-on-the-go' group, the risk of dementia appeared to be lower in the group that had been travelling by bike. This group also appeared to have a larger hippocampus volume. (The hippocampus is a brain structure located in the middle of the brain that is important for memory, but also for spatial orientation.) In people with dementia, the hippocampus is reduced in size, because nerve cells and their connections in the hippocampus slowly die off. That is why people with dementia experience problems with spatial orientation and their memory, among other things.

Cycling as a means for a healthy brain

The groups with an increased risk of dementia also seemed to benefit from cycling, but the risk reduction was smaller here. It also turned out that other brain regions in the cycling group were larger. The authors of the study therefore concluded that cycling in which moving images play a role could be a promising strategy for keeping the brain healthy.

And most importantly of all, the study actually shows two observations that take place simultaneously in a group: people who cycle regularly were less likely to develop dementia later in life compared to people who did not cycle. So there is a connection between cycling and a reduced risk of dementia, but the fact that cycling and a lower risk of dementia occur together in a group of people does not prove that cycling is the cause of that reduced risk. It may well be that people who cycle have better lifestyle habits than people who do not. Or other (as yet unknown) factors may also play a role. Additional research is therefore needed to better investigate and understand this connection.