Aging and Brain Function - What Are the Concepts?
A few years ago (2008) Ann-Charlotte Granholm, Ph.D., Director of the Center on Aging at the Medical University of South Carolina, wrote an interesting paper for the medical journal, Current Aging Science. She and her co-authors presented the concept that implies that as we age there are a number of factors that alter our brain and brain functions. The major functions that are altered by age are Mood, Memory, and Movement. It is well known that as we age we lose function in just about all organs, whether it be our muscles, our cardiovascular, reproductive, or many other physiologic systems. This is why we can't run like we used to nor have children. We also experience heart and brain attacks as we get older. Most of these processes are well understood and therefore we have preventive and or therapeutic options (except for reproduction in the female).
What About the Brain?
It is certainly well known that as we age our brain does not function like it used to either. In fact, it is common and expected that as we age we become more forgetful, not an all together bad thing ( if we forget unpleasant memories). We also have a much more overall gloominess or depressive times that can be interspersed with the same old joy as we age. Finally, as we age we subtly begin to lose such things as good balance and in some cases develop any one of several "movement disorders."
Because it is normal to lose function in all of these areas as we age, it is not appropriate to call the consequences of age in brain function abnormal unless the symptoms become so dysfunctional that they fall into recognized diseases. Some of these diseases are late life depression, characterized by clinical depression that requires medical treatment. The loss of memory can progress or result in the well known and greatly feared neurodegenerative disease known as Alzheimer's disease. This too calls for medical therapy when it is diagnosed, but it tends to progress even with optimal medical care. There are a very large number of movement disorders that result in abnormal movement, either too much, too little, or uncoordinated. A common movement disorder that increases with age is tremor, usually an intention tremor or one that occurs when we intentionally make a hand movement and the hands or fingers involuntarily begin to waiver or shake. One in five people (20%) over 65 will have intentional tremors and this is a common consequence of aging. Another very common movement disorder is Parkinson's disease that occurs in about one in five hundred people (0.2%). Parkinson's has specific treatment therapies and its progression can be slowed, but like Alzheimer's, the disease tends to progress impairing quality of life and increasing dependency on others.
A Multifaceted Cause
Dr. Granholm's concept of causes of the age-related neurodegenerative diseases is illustrated in the figure below. As we age we experience a wide array of different factors that collectively impact the function of the brain. The end result is that we have mood changes, movement disorders and memory loss. Although we tend to think of these as independent consequences of age, it turns out they are interrelated in terms of cause and effect. For example, someone with memory loss often has more depressive times and certainly is not as agile as at a younger age. There is a reason that there is a commonality in the expression of these age-related changes, they all result from neurodegeneration, meaning loss of brain structure and function. Furthermore, the many factors that cause neurodegeneration cause loss of function in mood, movement, and memory.
Cause of Neurodegeneration
The biochemical, endocrine, biological, and structural causes of neurodegeneration are neuron (nerve) destruction, oxidative stress, growth factor loss, hormonal changes, and imbalance, inflammatory responses, and protein aggregation. These are medical terms that describe everyday events that become cumulative as we age. For example, the body mounts an inflammatory response to infection and various other stresses that batter the body as we age. The more of these stresses we have, the more it adversely affects the brain, particularly in "susceptible" individuals. What makes one "susceptible" is often our genetic ability to protect the brain from any of the factors illustrated in the figure that bombard the body. This is why some of us have disorders of aging, but others don't and neither did our parents or siblings. The many genes in our body can defend us or make us vulnerable to aging's onslaught.
What Can Be Done?
Sadly, as we age we can expect the brain to continue to be under the unremitting factors that erode function. However, some of the proven in animal and man protections against some of these offending factors are known. To combat oxidative stress, we should have antioxidants in our diet. Some of the tasty antioxidants that we should eat in abundance are strawberries, blueberries, pecans, and a variety of beans. Another factor shown to combat some of the factors in the figure is regular exercise. It is important to be on a regular exercise routine and be faithful to it. This has been shown in mice and men to be protective against some of the factors that tend to cause neurodegeneration.
The Bottom Line
Aging obviously beats the alternative, but as we continue to put the years on we can expect that all-important organ, the brain, to suffer damage from many different factors that conspire to cause mood, memory, and movement deterioration. We must be aware of these changes in function and seek medical attention when we develop the disease states of depression, Alzheimer's, and movement disorders like Parkinson's disease. There are medicines and in some rare cases surgery that can help ameliorate the diseases. Finally, diet and exercise are effective in preventing some of the factors that contribute to our brain's decline.
The figure shows the many factors that affect brain function and ultimately lead to neurodegeneration that causes mood changes, movement disorders, and memory loss in the brain. The longer we live, the greater the cumulative negative impact the factors have on brain integrity and function. The genetic makeup (Genetics in the figure) of each of us can be a protective wall against these destructive factors or our genes can make us more vulnerable.
Figure altered from: Granholm et al. Current Aging Science 2008, 1, 134.