Modifiable Risk Factors for Neurodegenerative Disease

Further to those fixed elements of age and genetics, we also know that there are many risk factors for a neurodegenerative disease that can, through lifestyle, behavioural and societal changes, be modified and even have the potential to be eliminated.

The modifiable factors for which we have the greatest level of evidence have been compiled in the Lancet commission report on dementia prevention, intervention, and care. The Lancet commission report looks at the sum of all existing evidence around risk factors and concludes that, while 60% of all dementia cases are thought to be the result of genetics and as yet unknown causes, eliminating 12 potentially modifiable factors on a population-wide level would lead to a projected 40% decrease in the total cases of dementia.

In other words, if we were able to wave a magic wand and completely remove the 12 risk factors listed in the diagram above from the planet, we would then see 40% less people developing dementia. Therefore this proportion of overall dementia cases is, in theory, preventable.

In practice, we don’t have a magic wand and you’ll notice from studying the list that many of these risks have complex multi-factorial causes themselves. However, what this summary of the evidence base does give us is some really clear key areas to focus attention on for effective prevention of dementia.

What’s Good for the Heart Is Good for the Brain

Our brain is an energy-intensive organ and as such, it is also a very thirsty one. Much like a high-powered sports car rapidly consuming petrol, our brain requires a rich blood supply to perform at its best. Although the brain only accounts for around 2% of our total body weight, it receives almost 20% of blood output pumped from the heart. Any disruption to that blood supply can be detrimental to brain functioning and leave our brains vulnerable to disease processes.

Looking at our list of 12 risk factors above, we can clearly see a link between what we classically think of as ‘heart health’ and brain health. Hypertension, excess alcohol, obesity, smoking, physical inactivity, air pollution and diabetes are all known to affect our cardiovascular health.

Cognitive Stimulation –Socially and Intellectually – Is Important Throughout Our Lives

Looking at our list of risk factors, we also see that those not so directly related to our cardiovascular health cluster around important themes of education and social interaction.

The identification of these elements as risk factors reinforces the fact that we should keep challenging our brains by learning new skills throughout life and that we should remain socially engaged.

This stimulation is important for maintaining the effective functioning of our brain but also to build up resilience to disease processes.

We know from post-mortem research studies that not everyone is affected equally by neurodegenerative pathology being present in the brain. Two individuals who might be classed as having a very similar degree of pathology in the brain can have very different presentations in terms of the severity of symptoms and functional impairment they experience in life.

One leading theory for why this might be is explained through the concept of cognitive reserve. The idea behind cognitive reserve is that if we have a richer network of pathways built up in our brains, through a greater number of interlinked brain cell connections, then we may be able to tolerate a certain degree of brain damage without experiencing any symptoms. In other words, this richer network of brain connections makes us more resilient and able to adapt and cope with early brain disease processes.

One way to think about this is to picture a car traveling along a road to reach its desired destination. Let’s imagine the route becomes blocked, say by a tree falling on the road. If there’s only one possible route to take then the car is stuck and can no longer reach its destination (figure A below).

However, if there are a multitude of alternative roads to choose from, then we can perhaps make a diversion, take another route, and still arrive at that desired destination (figure B below).

This is the basic principle of cognitive reserve. The greater the network of possible pathways (or brain connections) we have built up over life, the greater our capacity to adapt and re-route when a disease process (much like a fallen tree) disrupts one of those paths.

The 12 factors listed above are not the only risks that we know of. The Lancet report only includes areas that we have the best quality evidence for. More research is adding to our knowledge all the time and undoubtedly this list of modifiable factors will continue to grow. Research findings will also continue to chip away at the ‘risk unknown’ portion.

What other factors can you think of, not covered here, that might be linked to risk for, or protection from, the neurodegenerative diseases that cause dementia?