Everyone has a sense of time passing. Obviously, we all have a greater chance of dying as we get older, yet, after age 90, something strange happens and our mortality rate starts slowing as we gradually approach 114 years of age. Therefore, the calendar does always represent how old our brains, or bodies, feel to us. Clearly, our brains suffer the consequences of our everyday experiences, such as poor diet, alcohol, injury, etc. Does our brain age as fast as we do, or faster? The answer to this important question depends upon so many other factors. Being female is clearly better than being male because females live longer than males; this is true whether you're a spider, a fly or a human. If your parents were long-lived then you are likely to live a long life as well. Wealthy, educated people almost always live longer than poor, uneducated people. One reason is diet: healthy diets tend to be more expensive than unhealthy diets. Therefore, it's not surprising that skinny people live longer than obese people. I've touched on the reasons why in other blogs: Obese-or-lean-how-your-brain-decides; Good fat, Bad fat.
Our concept of what underlies normal aging has evolved over time. During the 19th century it was thought that our "vital humors" simply ran out and we died. Later, "humors" were replaced with the more scientific term "energy'; once you used up all it, you died. This was analogous to burning the candle at both ends, or a "live fast-die fast" mentality. During the 1950s humors and energy were now represented by heartbeats, i.e. you only get so many and once you reached that maximum number of heartbeats you died. Naturally, this concept discouraged exercise! Essentially, our view today of aging has become a balance between the "wear and tear" forces acting upon us from the environment and "programmed" influences such as our genes acting upon us intrinsically.
What happens inside the brain? The most obvious change when one looks at the brain is that our brain loses weight and shrinks a little; however, only a few ounces are lost by age 80 and most of that is water. Thus, our brains do dry out as we age. Drinking more water will not help and living in a dry climate does not place us at increased risk of shrinkage. It was once thought that the primary contribution to cognitive decline with aging was massive brain cell loss. Today we know that this is not true; the changes occurring during normal aging are more subtle and selective. Overall, it simply requires more to get our brain's attention. Older people need stronger light to read something, louder volume to hear the music playing, stronger pressure to sense touching and stronger tastes and odors to enjoy food or wine. Oddly, sweet and fruity odors are the most vulnerable to age-related changes while musky or spicy odors are relatively stable with aging.
Most cognitive abilities worsen, including inductive reasoning, spatial orientation and verbal memory. The loss of spatial orientation ability underlies a common problem for the elderly, wandering. The shrinkage of one particular brain region, the hippocampus, is most likely responsible for this loss of orientation and wandering.
When does aging of the brain begin? Probably as soon as the end of puberty. One recent study concluded that aspects of age-related cognitive decline begin in healthy educated adults when they are in their 20s and 30s. One example of an early change in brain function is sleeping. People enjoy their best sleep when they're about ten years old, i.e. our sleep is the deepest and we are quite awake during the day. From that point on, things deteriorate; we all know what that feels like. As we get older we spend less time in dream sleep and also less time in the deeper stages of sleep. The worsening of our sleep quality correlates directly with our poor cognitive abilities when we're awake.
Whose brain ages the slowest and can we do anything about it? Fortunately, there are some great answers to these questions; they're just not always the ones we would like to hear. To save you the time reading all of my other blog posts, here is my compilation of the best advice for living long and having a healthy brain: be female, drink lots of coffee, choose your parents carefully, eat as little as possible, breathe as little as possible, move as little as possible, be born in May, be tall and have a large head, develop arthritis and then take lots of anti-inflammatories, smoke cigarettes for a short time when you're young and always drink moderate amounts of beer. If you must eat lots of food, then only eat at Indian restaurants. Finally, smoke one puff of marijuana every day, especially as you age. See Maintaining memories with marijuana.
© Gary L. Wenk, Ph.D. Author of Your Brain on Food (Oxford, 2010)