The Science Behind The Human Aging Process.
The Science of Human Aging
By Robert Johnson - Researcher
The science behind the human aging process is well established. Aging is a biological phenomenon that affects all living organisms. The aging process in humans has been studied and well documented for many years. Scientists and medical experts have analyzed almost every aspect of the human aging from birth to death of “Old” age. They have focused on the creation, maturation, and degeneration of all parts of the human anatomy, down to the cellular level. They have investigated the multitude of factors, both internal and external, which affect the health and wellness of our bodies, as well as the “natural” phenomenon of the life cycle.
For the sake of addressing those issues which deal with the “after peak” homeostasis of the average human being, we will skip past the birth to maturity phase of human physical development. However, that is not to say that any number of factors, such as environmental conditions, eating habits, exposure to nature, etc. can have a major contributing effect on individual aging processes.
The causes of aging are complex; current theories are assigned to the damage concept, whereby the accumulation of damage (such as DNA oxidation) may cause biological systems to fail, or to the programmed aging concept, whereby internal processes (such as DNA telomere shortening) may cause aging. Programmed aging should not be confused with programmed cell death (apoptosis).
Effects of aging
Enlarged ears and noses of old humans are sometimes blamed on continual cartilage growth, but the cause is more probably gravity.
Comparison of a normal aged brain (left) and a brain affected by Alzheimer’s disease (right).
A number of characteristic aging symptoms are experienced by a majority or by a significant proportion of humans during their lifetimes.
- Teenagers lose the young child's ability to hear high-frequency sounds above 20 kHz.
- Some cognitive decline begins in the mid-20s.
- Wrinkles develop mainly due to photoaging , particularly affecting sun-exposed areas (face).
- After peaking in the mid-20s, female fertility declines.
- People over 35 years old are at risk for developing presbyopia and most people benefit from reading glasses by age 45–50. The cause is lens hardening by decreasing levels of α-crystallin, a process which may be sped up by higher temperatures.
- Hair turns grey with age. Pattern hair loss by the age of 50 affects about half of males and a quarter of females.
- Menopause typically occurs between 49 and 52 years of age.
- In the 60–64 age cohort, the incidence of osteoarthritis rises to 53%. Only 20%, however, report disabling osteoarthritis at this age.
- Around a third of people between 65 and 74 have hearing loss and almost half of people older than 75.
- By age 80, more than half of all Americans either have a cataract or have had cataract surgery.
- Frailty, defined as loss of muscle mass and mobility, affects 25% of those over 85.
- Atherosclerosis is classified as an aging disease. It leads to cardiovascular disease (for example stroke and heart attack) which globally is the most common cause of death.
- The maximum human lifespan is suggested to be 115 years "for the foreseeable future". The oldest reliably recorded human was Jeanne Calment who is said to have attained 122 years and died in 1997.
Dementia becomes more common with age. About 3% of people between the ages of 65–74 have dementia, 19% between 75 and 84 and nearly half of those over 85 years of age. The spectrum includes mild cognitive impairment and the neurodegenerative diseases of Alzheimer’s disease, cerebrovascular disease, Parkinson’s disease and Lou Gehrig’s disease. Furthermore, many types of memory may decline with aging, but not semantic memory or general knowledge such as vocabulary definitions, which typically increases or remains steady until late adulthood. Intelligence may decline with age, though the rate may vary depending on the type and may in fact, remain steady throughout most of the lifespan, dropping suddenly only as people near the end of their lives. Individual variations in rate of cognitive decline may, therefore, be explained in terms of people having different lengths of life. There might be changes to the brain: after 20 years of age, there may be a 10% reduction each decade in the total length of the brain's myelinated axons.
Age can result in visual impairment, whereby non-verbal communication is reduced, which can lead to isolation and possible depression. Macular degeneration causes vision loss and increases with age, affecting nearly 12% of those above the age of 80. This degeneration is caused by systemic changes in the circulation of waste products and by the growth of abnormal vessels around the retina.
A distinction can be made between "proximal aging" (age-based effects that come about because of factors in the recent past) and "distal aging" (age-based differences that can be traced back to a cause early in person's life, such as childhood poliomyelitis).
Ageing is among the greatest known risk factors for most human diseases. Of the roughly 150,000 people who die each day across the globe, about two thirds—100,000 per day—die from age-related causes. In industrialized nations, the proportion is higher, reaching 90%.
When we use the term “anti-aging” this a reference to a number of dietary adjustments, the use of specially formulated ingredients and compounds, physical exercises, in effect lifestyle changes which, if made habitual, promote a youthful appearance with increased bodily energy. This will be discussed in more detail elsewhere in these pages.