Aging encompasses two primary dimensions. The first is biological, marked by the gradual decline of physiological and mental functions in our body. The second is psychological, as evidenced by studies from the Stanford Center on Longevity, showing that individuals tend to narrow their focus on significant activities and relationships as they age.
The psychological aspect proves more complex to define subjectively. For instance, some people may consider themselves old and limit their activities by the age of 40, while others at 60 may expand their pursuits and social connections.
Biologically, age-related changes are relatively consistent. Aging markers abound within the body, and physiological functions decline to varying and quantifiable degrees with advancing age. In an ideal scenario of balanced public health, all individuals would begin biological decline around the same age (typically between 25 and 30 years).
However, reality is different. Numerous factors influence the aging process, either hastening or decelerating it. While an exhaustive list of these parameters isn’t feasible, science has identified key factors like genetics (including nationality), diet, pollution, occupation, UV exposure, exercise, and overall lifestyle.
Each of these elements exerts its influence on aging, with either positive or negative impacts. For instance, a well-rounded diet minimizes free radicals and oxidative molecules, thus reducing cellular stress. On the other hand, continuous exposure to pollution can harm mucous membranes and organic tissues, while regular physical activity diminishes the formation of fatty deposits and enhances oxygenation.
Each parameter and its variations uniquely shape the pace and extent of aging. Nonetheless, aging remains quantifiable and assessable through various biological markers. From cells and bones to muscles, eyes, and skin, our body’s entire biology transforms as we age.
Diminution in the Number of Cells: A Matter of Telomeres
Cells undergo programmed death, known as apoptosis, due to genetic triggers that initiate a process resembling cellular suicide. This mechanism is crucial for clearing out old cells to make way for new ones, with factors like cell aging, excessive cell numbers, and damage acting as triggers. Another reason for cell death lies in their limited ability to divide, set by genetic programming. Once cells exhaust their division capacity, they grow, persist for a period, and ultimately die.
The process of cell division limitation involves telomeres, which cap chromosome ends. With each division, telomeres shorten, and when they reach a critical length, the cell loses its ability to divide, entering a state termed senescence.
Additionally, cells can perish due to direct damage caused by external factors. Harmful agents like radiation, sunlight, and certain drugs such as chemotherapy can harm cells. Cells may also sustain damage from byproducts of their regular activities, known as free radicals, produced during energy generation processes.
In summary, cell death stems from programmed processes, genetic limitations on division, and exposure to external stressors, contributing to tissue renewal and maintenance within the body.
Organs: After the Age of 30, They Begin a Gradual Decline
The proper functioning of organs relies on the optimal performance of the cells comprising them. However, aging leads to diminished cell efficiency and, in some cases, a reduction in cell count within specific organs. Organs such as the testicles, ovaries, liver, and kidneys experience a notable decrease in cell numbers as individuals age, impairing their ability to function normally. Consequently, most organs tend to exhibit decreased functionality with age.
Yet, not all organs undergo substantial cell loss. The brain is an example of this, as healthy elderly individuals typically do not experience significant brain cell reduction. Significant cell loss is more prominent in cases of stroke or progressive nerve cell loss disorders, such as Alzheimer’s or Parkinson’s disease.
Often, the earliest signs of aging involve the musculoskeletal system. The eyes, followed by the ears, begin to change in the early forties. Most internal functions also decline with aging. Most bodily functions peak shortly before the age of 30 and then begin a gradual but continuous decline.
Despite these declines, most functions remain adequate due to organs having a functional reserve—initial functional capacity that exceeds the body’s requirements. For example, if a portion of the liver is damaged, the remaining tissue can still maintain normal function. Consequently, pathological disorders, rather than normal aging, primarily contribute to functional loss in older individuals.
Although most functions remain sufficient, the reduced capacity to handle various stresses becomes evident in older individuals. Challenges like intense physical activity, extreme temperature fluctuations, and injuries may be more taxing on their bodies. Additionally, older individuals are more susceptible to medication side effects. Certain organs, including the heart and blood vessels, urinary system (such as kidneys), and brain, are more likely to malfunction under stress.
Bones, Cartilage, and Ligaments: Witnesses of Aging
Bones have a tendency to experience reduced density as time passes. A moderate decline in bone density is known as osteopenia, while a more substantial reduction in density, including instances of fracture due to weakened bone structure, is termed osteoporosis. Osteoporosis renders bones more fragile and susceptible to fractures. In women, the decrease in bone density accelerates post-menopause owing to diminished estrogen production. Estrogen plays a crucial role in preventing excessive bone breakdown during the normal progression of bone formation, breakdown, and remodeling.
One reason for the decrease in bone density is the lower calcium content within bones, which contributes to their strength. This reduced calcium content results from the body absorbing less calcium from food. Moreover, levels of vitamin D, a key factor in facilitating calcium utilization, experience a slight decrease. Certain bones are more vulnerable than others, with notable impact areas being the upper part of the thigh bone near the hip, the ends of arm bones near the wrist, and the spinal vertebrae.
Alterations in the upper spinal vertebrae can cause the head to tilt forward, compressing the throat. This phenomenon leads to difficulties in swallowing and increases the likelihood of choking. Vertebrae also experience a decrease in density, while the cushioning tissue (discs) between them loses fluid and thins, resulting in a shortened spine. Consequently, elderly individuals often experience a reduction in height.
The cartilage lining the joints tends to thin out, partially due to wear and tear resulting from years of movement. Joint surfaces may not glide as smoothly over each other as before, and joints could become somewhat more prone to injury. The deterioration of cartilage from daily joint use or repeated injuries frequently results in osteoarthritis, one of the most prevalent age-related conditions.
Ligaments, responsible for connecting joints, and tendons, which attach muscles to bones, tend to lose elasticity, leading to sensations of tightness or stiffness in the joints. These connective tissues also weaken, causing a decrease in overall flexibility for most individuals. Ligaments and tendons become more susceptible to tearing, and when injuries do occur, the healing process tends to be slower. These transformations stem from reduced activity levels in the cells responsible for maintaining ligaments and tendons.