Analyzing Theories of Aging to Better Understand the Question ‘Why Do People Age’

Everybody gets older—it’s just a fact of life. At different ages, however, aging can have different connotations. Throughout infancy, childhood, and adolescence, aging means growth—both physical and emotional.

But what does aging entail once you’re an adult? Early adulthood is typically when your body is in peak physical form. Naturally, this doesn’t last forever. So, as you move from early adulthood into middle age and on, you’ll likely notice gradual changes in how your body feels and what it can do.

Unfortunately, there’s no stopping these changes. But there are theories of aging that try to answer that difficult question: why do people age?

The answers you’ll read below can help provide background knowledge you can use to set yourself up to age as comfortably as possible. And a great place to start is the what, why, and how of aging. What should you expect as you age? Why do these changes occur? And how can you deal with them as they come?

Why Do People Age?

Aging is an incredibly complex process that scientists still do not fully understand. As such, there’s no easy answer as to why humans age. Here’s what is known: the cells in the body wear out over time. Their functionality decreases and their structure deteriorates. Scientists attribute this decline to a combination of factors sorted into two categories: intrinsic and extrinsic.

• Intrinsic aging: You’re going to age regardless of your lifestyle. After all, even the healthiest people grow old. This naturally occurring aging process is known as intrinsic aging. It’s simply biologically predetermined that your cells will eventually deteriorate.
• Extrinsic aging: There are numerous lifestyle and environmental factors that also affect aging. Smoking, heavy drinking, and air pollution can all age your cells. This is known as extrinsic aging because it is determined by factors outside of your body.

Although it rarely comes up in conversation, the distinction between intrinsic and extrinsic aging is something most people are already aware of—they just don’t realize it. A middle-aged smoker might remark that they “have the lungs of an 80-year-old.” People would understand that statement because most are already aware that external—or extrinsic—factors can influence the aging process.

This leads right into two more key terms related to aging: biological age and chronological age.

• Chronological Age: This is the number you give when someone asks how old you are. In other words, chronological age is the amount of time that has elapsed from your birth to the present. There’s no speeding or slowing the progression of chronological age.
• Biological Age: Aging occurs as the cells in the body are damaged and deteriorate. This process is inevitable and, in relatively healthy individuals, occurs at roughly the same rate. So if you look at the cells of a healthy, 30-year-old woman, her biological age is probably about 30. If an individual has been exposed to extrinsic factors of aging—say they’re a heavy smoker—their cells will “age” more rapidly. And their biological age might be closer to 50 while their chronological age is 30.

Think back to that first question: why do people age? You now know aging is the gradual breakdown or deterioration of the cells in the body. This process happens naturally but can be sped up through a variety of external factors.

That’s a pretty simple concept, but this explanation does bring up another question, though. Why do the cells in the body naturally deteriorate? It’s not a process that benefits individuals. Most detrimental processes are weeded out through thousands of years of natural selection. So why haven’t humans evolved to have endlessly healthy cells? This is where the different theories of aging come in.

Explaining the Theories of Aging

There’s no scientific consensus around how or why the cells in the human body gradually and inevitably deteriorate. There are factors known to speed the aging process up, but there aren’t any proven methods for slowing the aging process beyond its natural rate.

This leaves a big question: why?

Scientists’ answers to this enigma fall into one of three categories: program, damage, or combined theories of aging. As you read about each theory of aging, remember that they offer possible explanations for humans’ limited lifespan, but no conclusive answer.

• Program Theories of Aging: Scientists in this school of thought believe aging is not an accident. They think humans have evolved to age and eventually die. That makes the whole process a deliberate, programmed part of human genetics.
  From an evolutionary standpoint, this might feel a little bit backwards. Why would human evolution progress in a way that led to a fixed lifespan? The answer is altruism—not deliberate selflessness, but the development of evolutionary traits that benefit the species, not the individual.
  There are finite resources in the world. If humans lived forever, there would be fierce competition for those resources. One explanation for aging is that humans have evolved to die once they reach a post-reproductive age, leaving less competition for the younger generations.
• Damage Theories of Aging: As mentioned above, it’s widely accepted that certain environmental factors can speed the aging process. Damage theories of aging follow a similar line of logic. These theories of aging pin humans’ eventual death on the gradual accumulation of damage to the cells, not a predetermined or preprogrammed genetic feature. The source of this cellular damage, however, is up for debate.
  One common theory is that natural processes of the body subject cells to small amounts of oxidative stress. That is, some body processes create byproducts that damage cells. Metabolism, for instance, creates reactive oxygen species (ROS) that cause tissue and cell damage over time.
• Combined Theories of Aging: As the name suggests, combined theories of aging draw from program and damage approaches to create a comprehensive explanation.
  During the 1970s, B.L. Strehler, a scientist who studied old age, introduced four postulates (or assumptions) about aging. First, aging is universal and occurs in all species. Second, aging is intrinsic. Third, aging occurs incrementally. And, finally, factors are only part of the aging process if they hold no evolutionary advantage.
  Most modern combined theories of aging are based on these four postulates. They tend to focus on the specific ways cells deteriorate. (Is it the cell membrane? Or does aging have to do with the ability of cells to generate electricity?) But, again, despite the theories, there is no consensus on the central question: why do people age.

What to Expect as You Move Through the Stages of the Aging

A deep dive into the science of aging, though interesting, can sometimes shift the discussion too far from the effects of aging. Your cells deteriorate each day—that’s what aging is. But what impact does that have on your lived experience?

The effects of aging are perhaps best summed up by a common phrase. When describing an older relative or friend, you might say they are “slowing down.” And there’s a lot of truth in that statement. The aging process causes the body to operate less effectively and efficiently than before. This affects various body systems and processes. Whether it’s bouncing back from an injury, building muscle, or even moving around, everything gradually slows down.

The aging process is often described in five chronological stages or phases:

• Independence: During this period, most individuals may notice their body slowing down a bit, but everyday tasks are still manageable. This period is mostly a continuation of regular adult life, but it is a good time to start thinking about future plans and needs.
  
• Interdependence: This is the stage of life when everyday tasks begin to grow more difficult. Adults in the interdependence stage of old age are often able to live independently, but may require additional help with cooking, driving, and similar tasks. In most instances, a full-time caretaker isn’t necessary.
  
• Dependency: As the name suggests, the dependency stage is when adults begin to lose the ability to live on their own. This stage comes at a different time for everyone. Physical and mental health play the biggest role in determining when adults reach the dependency stage. This can be an incredibly difficult and frustrating time, as the transition to having a full-time caretaker (a family member or professional) can be a jarring, unwelcome change.
  
• Crisis management: This stage is when an individual requires more care (whether it’s medical or day-to-day assistance) than family members and other loved ones can provide. At this point in life, many individuals may need to relocate to a full-time care facility.
  
• End of life: The end result of aging is, naturally, death. This stage looks very different for everyone depending on their needs. Many individuals will reside in a hospital, care facility, or hospice center, while others may live with relatives. The focus should be on providing an individual as much comfort, love, and care as possible during this final stage of life.

How to Deal With Aging

If there’s one fact that you’ll need to get comfortable with, it’s that you’re going to age. There’s nothing you can do to stop it. You can, however, take steps to make aging as comfortable as possible.

To do this, go back to the basics of a healthy lifestyle:

• Eat a healthy diet (full of vegetables, fruit, beneficial fats, lean proteins, and fiber-rich whole grains)
• Avoid smoking
• Drinking only in moderation
• Exercising regularly
• Manage stress in a healthy way

These lifestyle habits will help you continue to maintain normal levels of oxidative stress on your cells. And, in turn, you’ll help keep your biological age in line with your chronological age.

Additionally, consider ways to support your cellular health. Since aging is the deterioration of your cells, taking care of your cells is just about the best way to optimize aging as much as possible.

Beyond practicing healthy lifestyle habits, take the time to be mindful of the present. Each stage of life has its joys and setbacks. Take them as they come and enjoy wherever you happen to find yourself in the aging process!