It’s trivia night, it’s your turn, and you’re in luck…You’ve just been asked to name the main character in a classic movie you just watched two nights ago! But uh-oh. For some reason, no matter how hard you think, you just can’t come up with the character’s name. In the moment, you laugh it off, but later when you’re by yourself you begin to wonder, “How could I possibly have forgotten that? Am I losing my memory? Am I in the early stages of Alzheimer’s?” What causes memory loss and these incidences of forgetfulness?
Chances are, you’re not. But if this sort of thing has been happening to you more and more lately, you could well be experiencing age-related memory loss. If so, why? What causes memory loss and forgetfulness? Is there something you might have done differently to prevent it, or anything you could be doing now to stave it off?
Before delving into the causes of memory loss, it’s important to distinguish between various aspects of memory deficit. Memory lapses are not the same thing as memory loss, nor is memory loss the same thing as a disease such as dementia. When we conflate these terms or lump them together, it’s easy to become confused. The causes of lapses, loss, and disease, while sometimes overlapping, are not identical.
A memory lapse is an instance of forgetfulness. Memory lapses happen to all of us, whether we’re four years old, 14, 40, or 94, and whether our brains are perfectly healthy or not. Experiencing a lapse of memory is simply a part of life, and, in and of itself, it does not indicate a major problem. However, memory lapses are the stuff of which cognitive decline is made. In other words, serious memory loss or dementia disease will manifest through frequent (and usually increasingly frequent) lapses.
Memory “loss” signifies a decline from a previously more favorable general cognitive state. If you have 15 memory lapses in a day but you’ve always had 15 memory lapses per day, you have not experienced memory loss. But going from two lapses per day to 15 would suggest that you have lost some of your memory capacity.
As they enter middle age, most adults begin to experience some memory loss. However, the typical age-related changes to memory are not considered problematic. It is only when a patient’s memory loss is shown to be more profound than should be expected for their age that we begin to discuss cognitive deficits in terms of either mild cognitive impairment (MCI) or dementia. Problematic memory loss can also occur after stroke and other types of brain injury.
To understand why we forget, it’s helpful to learn a little about how we remember. Human memory can be categorized in many ways, but for now we’ll focus on the two categories we think of most often…short-term memory and long-term memory. As the names suggest, short-term memory refers to the ability to recall information stored only briefly, while long-term memory refers to the ability to recall information stored over a prolonged period. In both of these forms, the memory process is similar. Memory works in three stages:
Any one or more of these processes can be disrupted, resulting in a memory lapse. Let’s imagine an example in which a wife shouts into the next room to ask her husband to pick up a gallon of milk later. Unfortunately, when she makes her request, the husband is searching for his phone charger, late for work, and rushing to get out the door. This distracted state causes him to fail to encode her request because she didn’t have his full attention. Or maybe he managed to shut out his distracting thoughts such that her request registered just fine, but before he could mentally repeat it to himself (that is, before he could complete the storage process), his phone rang and he saw it was his boss on the line. Or perhaps the encoding and storage processes went just swimmingly, and in the evening he leaves the office fully intending to stop by the grocery store, but during the process of retrieving the memory during the drive, someone dangerously cuts him off in traffic, commandeering his thoughts for the next 15 minutes until he pulls into the driveway empty-handed.
As these examples make clear, distraction, stress, emotion, indifference, or simple lack of focus can all be drivers of the kinds of memory lapses that occur in young, healthy brains.
Several conditions and factors can lead to memory loss, including infections, brain injuries, tumors, medications, sleep apnea, depression and anxiety, thyroid problems, nutritional deficiencies, and drug and alcohol abuse.
However, the most common condition associated with memory loss is aging. Sometime during our 40s, most of us experience a slowing in our reasoning skills and find it more difficult to commit new information to memory. This pattern continues for the remaining decades of our lives.
We still don’t know exactly why we begin to experience short-term memory loss as we age. Researchers have identified a host of factors, including educational level, race, socioeconomic status, depression, parental income, and occupation. We know that the brain naturally undergoes physical changes as we age. Our brains begin receiving less blood flow, and parts of the brain closely tied to memory start to literally shrink. The growth and repair of neurons (brain cells) is also diminished as production of important hormones and proteins declines. A poor diet and lack of exercise can exacerbate these brain changes.
Dementia is a broad term that encompasses changes to parts of the brain where neurons stop working properly and stop connecting properly with each other. In autopsies of people with Alzheimer’s disease, for example, examiners typically find deposits of amyloid plaque in the affected areas of the brain. Researchers have identified genetic variants that make some people susceptible to certain forms of dementia, but scientists are still working hard to understand the role of inflammation, diet, and lifestyle on the development of dementia.
It can be very difficult to sort out whether your memory lapses result from actual structural changes to the brain, side effects of medications, sleep deprivation, stress and anxiety, or some combination of these. If you’ve noticed a pattern of worsening memory lapses, start a conversation about it with your doctor.
