While people age differently, certain physiological and cognitive changes are nearly universal and expected—this is known as usual aging, or senescence. An example that most people experience is the need for reading glasses, a condition called presbyopia, which typically begins in midlife. This occurs because the lens of the eye stiffens and loses its ability to focus on close objects, a perfectly normal and unavoidable change.
Other Common Examples of Usual Aging
Beyond vision changes, usual aging involves a wide range of gradual bodily shifts. These are not considered diseases but are intrinsic to the aging process itself.
- Musculoskeletal System: A progressive loss of bone density (osteopenia) begins in midlife, making bones less strong and more prone to fracture. Muscle mass and strength also decrease over time, a condition known as sarcopenia, which can lead to reduced strength and balance. The cartilage cushioning joints wears down, contributing to stiffness and less flexibility.
- Cardiovascular System: Blood vessels and arteries gradually become stiffer, forcing the heart to work harder to pump blood. While a healthy older heart can function well, its ability to respond to strenuous activity is reduced. This can lead to a slight increase in blood pressure.
- Sensory Organs: Hearing loss, particularly of high-pitched sounds, is a common occurrence with age, called presbycusis. The ability to smell and taste can also diminish, which may reduce appetite and enjoyment of food.
- Skin and Hair: The skin becomes thinner, drier, and less elastic, which leads to wrinkles and age spots. Hair typically turns gray and can thin over time.
- Urinary System: The bladder becomes less elastic, and pelvic floor muscles may weaken, which can result in more frequent urination or minor incontinence. In men, the prostate gland often enlarges, which can also affect urination.
- Gastrointestinal System: As muscles in the digestive tract weaken, digestion can slow down, and constipation may become more common.
Comparing Usual Aging with Successful and Pathological Aging
It is crucial to distinguish usual aging from the other two main types: successful aging and pathological aging. Rowe and Kahn's model from 1987 first introduced the distinction, emphasizing that extrinsic factors can heighten the effects of aging.
| Aspect | Usual Aging | Successful Aging | Pathological Aging |
|---|---|---|---|
| Definition | Expected, gradual physiological decline influenced by typical extrinsic factors. | Minimal age-related loss of physiological function, often due to positive extrinsic factors. | Significant decline caused by disease processes, such as Alzheimer's or Parkinson's. |
| Example | Needing reading glasses (presbyopia) or a mild decline in mental function. | An 80-year-old remaining physically active, disease-free, and socially engaged. | A person with dementia who forgets entire events and struggles with daily tasks. |
| Extrinsic Factors | Neutral or negative influence, such as a sedentary lifestyle or typical environmental exposure. | Positive influence, including exercise, healthy diet, and social engagement. | Can be caused or exacerbated by negative external factors, like smoking or poor diet. |
| Prognosis | Gradual decline, but with functional reserves that remain adequate for daily needs for a long time. | Retention of high-level cognitive and physical function well into later life. | Severe and rapid decline in mental and physical capabilities, interfering with daily living. |
The Role of Intrinsic and Extrinsic Factors
Aging is influenced by a combination of intrinsic and extrinsic factors. Intrinsic aging is the chronological process driven by a person's unique genetic makeup and the slow, inevitable deterioration of cells. For example, the shortening of telomeres, which are the protective caps on chromosomes, is an intrinsic process that contributes to cellular aging.
Extrinsic factors are environmental and behavioral, including diet, exercise, smoking, and sun exposure. While some intrinsic changes are unavoidable, extrinsic factors play a significant role in modifying the rate and extent of usual aging. For instance, a person who maintains a healthy lifestyle may experience less severe effects of usual aging than someone with less healthy habits. This is why not all older people age at the same rate, even though the same fundamental biological processes are at play.
Conclusion
Understanding which is an example of usual aging helps normalize many common age-related experiences, from vision changes to reduced bone density. These predictable, gradual declines are distinct from severe, disease-driven deterioration. While aspects of usual aging are unavoidable, maintaining a healthy lifestyle—including diet, exercise, and social engagement—can play a significant role in mitigating its effects and supporting a higher quality of life. Regular check-ups with healthcare professionals are also key to differentiating between normal age-related changes and conditions that require medical intervention.
