A new study to be published in the Journal of Applied Physiology has confirmed that exercise can restore the decline in neural stem cells normally associated with aging.

The brain constantly produces new cells that differentiate into a wide variety of mature neurons in a process called neurogenesis. Particularly in the hippocampus, a decline in the numbers of new cells being produced can lead to problems with memory and learning.

This decline starts in middle age and the drop is precipitous, particularly in the dentate gyrus, an area of the hippocampus thought to contribute to new memories as well as having other functional roles. It is notable as being one of a select few brain structures currently known to have high rates of neurogenesis in adult humans.

Two hypotheses prevail as the cause of this decline – one is the overproduction of corticosterone that occurs in middle age, which results in a drop in stem cell production, and is the presumed mechanism by which chronic stress (another trigger of corticosterone production) can lead to depression. The second hypothesis is that adequate stem cell production relies on nerve growth factors in the brain that also decline with age.

This study looked at whether a deficiency of this factor, known as brain-derived neurotrophic factor (BDNF), led to reduced neurogenesis in this brain region.

To this end, they had mice running on treadmills and others living a relaxing lifestyle, and they looked at the levels of BDNF and its receptor (TrkB), and neuron numbers in their hippocampuses.

The results were impressive:

• Neural stem cell production increased by 200% in the exercising middle-aged mice compared with their sedentary controls
• The survival of new cells increased by 170%
• The growth of new cells increased by 190%

The effects were not limited to aged mice, either. In fact, the effects were even more enhanced in young mice.

This shows that:

• Excercise increased levels of both BDNF and TrkB
• Decreases in neurogenesis are due to BDNF and not corticosterone

So, if any of you life-extensionists out there didn’t know it already, here’s further evidence that exercise is not only good for your body, but crucially important for maintaining your mind, especially as one enters middle age. One wonders why middle age per se is the time when levels of this hormone tend to decline, perhaps it’s because people generally become less active as they get older. Either way, I won’t be canceling my gym membership any time soon!

Adapted from a press release provided by Eurekalert!