Neurogenesis – a lifetime process

The term neurogenesis refers to the growth and development of neurons. This process is at its most active while a foetus is developing in the womb.


Previously, neuroanatomists such as Santiago Ramon Cajal, believed the nervous system was a fixed system that was not capable of regeneration – but in 1962, the first evidence of adult neurogenesis was demonstrated by Joseph Altman. His findings were largely ignored by the scientific community until the 1980s, when research reignited interest in the topic by showing that neurogenesis occurs in rats and birds. Then, in the early 1990s, adult neurogenesis was also demonstrated in non-human primates and humans.


The evidence suggests that neurogenesis is critical to functions such as learning and memory because the production of new neurons is essential for these processes. This is why, when there is a loss of neurons these capacities go into decline, as can be seen in conditions such as Alzheimer’s and dementia generally.


Neurogenesis increases memory capacity, reduces the overlap between different memories and also helps maintain context with regards to the time and positioning of those memories. Other studies have clearly shown that maintaining the habit of learning is also linked to the survival of neurons. Interestingly, the latest research around exercise has shown that particularly cardiovascular exercise is advantageous to neurogenesis.



Exercise the miracle cure?

Exercise is a miracle cure, which we’ve always had, but for too long we’ve neglected to take our recommended dose. Our health is now suffering as a consequence. Whatever your age, there’s strong scientific evidence that being physically active can help you lead a healthier and even happier life.


People who do regular activity have a lower risk of many chronic diseases, such as heart disease, type 2 diabetes, stroke and some cancers. Research shows that physical activity can also boost self-esteem, mood, sleep quality and energy, as well as reducing your risk of stress, depression, dementia and Alzheimer’s disease.


You will often notice a ‘feel good sensation’ immediately following your physical activity, and most people also note an improvement in general well-being over time as physical activity becomes a part of their routine. This is because exercise releases endorphins, which create feelings of happiness and euphoria, which is why it is a wonderful antidote for many mental health conditions and can help prevent cognitive decline. As eluded to above, various studies have shown that cardiovascular exercise can create new brain cells (neurogenesis), which improves overall performance.


If exercise were a pill, it would be one of the most cost-effective drugs ever invented. This is because it delivers its results fairly quickly, has limited side effects and can be done at little or no economic cost to the patient.


Health benefits

Given the overwhelming evidence, it seems obvious that we should all, where possible, be physically active. It’s essential if you want to live a healthy and fulfilling life into old age.

It’s medically proven that people who do regular physical activity have:

• Up to a 35% lower risk of coronary heart disease and stroke
• Up to a 50% lower risk of type 2 diabetes
• Up to a 50% lower risk of colon cancer
• Up to a 20% lower risk of breast cancer
• A 30% lower risk of early death
• Up to an 83% lower risk of osteoarthritis
• Up to a 68% lower risk of hip fracture
• A 30% lower risk of falls (among older adults)
• Up to a 30% lower risk of depression
• Up to a 30% lower risk of dementia


So, physical activity…

• Improves your chances of living longer and living healthier
• Helps protect you from developing heart disease and stroke or its precursors, high blood pressure and undesirable blood lipid patterns
• Helps protect you from developing certain cancers, including colon and breast cancer, and possibly lung and endometrial (uterine lining) cancer
• Helps prevent type 2 diabetes (what was once called adult-onset diabetes) and metabolic syndrome (a constellation of risk factors that increases the chances of developing heart disease and diabetes; read more about simple steps to prevent diabetes)
• Helps prevent the insidious loss of bone density known as osteoporosis
• Reduces the risk of falling and improves cognitive function among older adults
• Relieves symptoms of depression and anxiety and improves mood
• Prevents weight gain, promotes weight loss (when combined with a healthy diet), and helps keep weight off after weight loss
• Improves heart-lung and muscle fitness
• Improves the quality of sleep



A modern problem

People are less active nowadays, partly because technology has made our lives easier. We drive cars or take public transport. Machines wash our clothes. We entertain ourselves in front of a TV or computer screen. Fewer people are doing manual work, and most of us have jobs that involve little physical effort. Work, house chores, shopping and other necessary activities are far less demanding than for previous generations.


So we move around less and burn off less energy than people used to. Research suggests that many adults spend more than seven hours a day sitting down, at work, on transport or in their leisure time. People aged over 65 spend 10 hours or more each day sitting or lying down, making them the most sedentary age group.



Sedentary lifestyles

Inactivity is described by the UK Department of Health as a “silent killer”. Evidence is emerging that sedentary behaviour, such as sitting or lying down for long periods, is bad for your health.


Too much sitting and other sedentary activities can increase your risk of cardiovascular disease. One study showed that adults who watch more than 4 hours of television a day had a 46% increased risk of death from any cause and an 80% increased risk of death from cardiovascular disease.


Becoming more active can help lower your blood pressure and also boost your levels of good cholesterol. Therefore, not only should you try to raise your activity levels, but you should also reduce the amount of time you and your family spend sitting down.


Previous generations were active more naturally through work and manual labour, but today we have to find ways of integrating activity into our daily lives.  So, people of all ages need find ways of reducing their sedentary behaviour.


Without regular physical activity, the body slowly loses its strength, stamina and ability to function well. People who are physically active and at a healthy weight live about 7 years longer than those who are not active and are obese.





Start Slow, Increase as Your Fitness Grows

The Physical Activity Guidelines for Americans (which are similar for Europeans) are general recommendations aimed at the general population. The problem with guidelines is that they try to cover as many people as possible. In other words, they aren’t right for everyone. How much exercise you need depends on your genes, your diet, how much muscle and fat you carry on your frame, how fit you are, and your capacity for exercise.


A study of more 7,000 men who graduated from Harvard before 1950 suggests that older people, those who are out of shape, or those with disabilities may get as much benefit from 30 minutes of slower walking or other exercise as younger, more fit people get from the same amount of more-intense activity.


In other words, if an exercise or physical activity feels hard, then it is probably doing your heart – and the rest of you – some good. If you are currently not active at all, it may be daunting to start out with 30 minutes a day of activity, five days a week.


So start with a shorter, less-intense bout of activity, and gradually increase over time until you can reach or exceed this goal. This ‘start slow, build up over time’ advice for physical activity applies to everyone, but it’s especially true for older adults, since starting slowly can help lower the risk of injury – and can make exercise more enjoyable.


There are numerous charts suggesting what is mild, moderate and vigorous activity, and these often use a formula that takes into account metabolic rates. However, these classifications can be somewhat misleading, because as we’ve said, there are so many factors that will determine your level of physical activity. So it is quite a subjective matter and you must make your own judgements about this.


That said, moderate-intensity aerobic activity means you’re working hard enough to raise your heart rate and break a sweat. One way to tell if you’re working at a moderate intensity is if you can still talk but you can’t sing the words to a song.


Examples of moderate-intensity aerobic activities are:

• walking fast
• water aerobics
• riding a bike on level ground or with few hills
• playing doubles tennis
• pushing a lawn mower
• dancing


Daily chores such as shopping, cooking or housework don’t count towards moderate-intensity aerobic activity. This is because the effort needed to do them often isn’t hard enough to get your heart rate up.


Vigorous-intensity aerobic activity causes more rapid breathing and a greater increase in heart rate, but you should still be able to carry on a conversation but with much shorter sentences.


Further Reflections

We began talking about neurogenesis, which would more commonly come under the heading of neuroscience and yet, as is increasingly becoming clear, these topics around health do not in fact stand alone – they are all indeed connected.

We’ve also discovered that exercising is one way of maintaining and increasing neuron production, which leads to greater neuroplasticity – our ability to keep learning, growing and improving. So making a commitment to some form of physical exercise, especially cardiovascular exercise, is also making a commitment to your brain health and old age. Growing old does not necessarily mean deterioration. That is determined by the decisions and choices we make.


Also see: Neroplasticity and Exercise and Happiness