My life, measured in years, approaches the number 50 at an alarming speed. Therefore it gives me chills to read about the impact of aging on the brain. It’s a fact, THE BRAIN SHRINKS WITH AGE. I feel I desperately need every single neuron, just to get through the day without embarrassing myself. The other day for example, I took a jug of orange juice and a dirty glass from the living room to the kitchen. An hour later when I went back in the kitchen, I noticed the jug of orange juice in the sink. When I opened the fridge to put the jug in it’s intended place, the dirty glass was there, sitting just beside the milk, mocking me … or so it seemed. Is this perhaps the first sign of the horrible impact of age on my brain?
The brain consists of gray and white matter. The cerebral cortex is the outermost part of the brain, about 2-5 mm thick and is often called the gray matter. Below the gray matter lies the white matter, which derives its name from a white sheath that covers nerve fibers in that area. The gray matter begins to shrink at an earlier age than the white matter, generally before the age of thirty. The thinning of the cortex is most prominent in the prefrontal cortex. The prefrontal cortex plays a significant role in various important functions, such as working memory, planning, self-control, initiative and emotional control. The thinning of the white matter begins in the fourth decade of life. The white matter shrinks at a faster rate than the gray matter and so becomes more extensive in the oldest age-group. The main function of the white matter is to pass messages between different areas of the brain.
The hippocampus is placed in the medial temporal lobe, beneath the cortical surface. The hippocampus plays an important role in memory and seems especially sensitive to the impact of aging. Research has shown that the hippocampal volume decreases only slightly before the age of 50, but the largest declines occurs after the age of 60.
The rate of decline increases with age and one reasearch estimated that between the age of 30 and 90, the average decline of the volume of the hippocampus is 35%, of the white matter 26% and of the gray matter 14%.
Does a considerable decline in brain-functions inevitably follow the process of aging?
No, apparently not!
Most of us know someone who has reached an old age without seemingly loosing anything of their cognitive abilities. The research cited above report average-measures from many individuals, and the variability in cognitive abilities is greater within the older age-groups than the younger ones. There is evidence that the effect of age on cognitive functions and brain structure are overestimated in these studies.
The lifestyle we choose has very much to do with how our brain ages. It is therefore partly in our own hands how we manage to hold on to our brain cells in old age. I will speak more of that later (see: Cardiovascular exercise is probably the simplest way to protect your brain against the influence of aging).
I’m sure (I think) that my aforementioned blunder is not caused by a massive loss of neurons. Loads of healthy young adults make a similar mistake, as is apparent in this post “I forget everything”. When I am done preparing my vegetable meal and have run a few miles, I will sit down and read up on what factors contribute to the maintenance of a healthy brain in old age. I will of course share my knowledge with you, dear reader, in my next posts!
Here is a video from Youtube.com were Jeff Burns, MD discusses physical brain changes that occur with aging and Alzheimer’s disease.
-Courchesne, E., Chisum, H. J., Townsend, J., Cowles, A., Covington, J., Egaas, B. o.fl. (2000). Normal brain development and aging: Quantitative analysis at in vivo MR imaging in healthy volunteers. Radiology, 216 (3), 672-682.
-Ge, Y., Grossman, R. I., Babb, J. S., Rabin, M. L., Mannon, L. J. og Kolson, D. L. (2002). Age-related total gray matter and white matter changes in normal adult brain. Part I: volumetric MR imaging analysis. American Journal of Neuroradiology, 23 (8), 1327-1333.
-Jernigan, T. L., Archibald, S. L., Fennema-Notestine, C., Gamst, A. C., Stout, J. C., Bonner, J. o.fl. (2001). Effects of age on tissues and regions of the cerebrum and cerebellum. Neurobiology of Aging, 22 (4), 581-594.
-Hedden, T. og Gabrieli, J. D. E. (2004). Insights into the ageing mind: a view from cognitive neuroscience. Nature Reviews Neuroscience, 5 (2), 87-96.