Ageing
Ageing is the accumulation of changes over time, affecting most organisms.
Ageing (or aging in American English) is the process of becoming older. The term refers mainly to humans, many other animals, and fungi; whereas for example, bacteria, perennial plants and some simple animals are potentially biologically immortal. In a broader sense, ageing can refer to single cells within an organism which have ceased dividing, or to the population of a species. In humans, ageing represents the accumulation of changes in a human being over time and can encompass physical, psychological, and social changes.
- field
- Biology, Gerontology
- known_for
- Process of becoming older; accumulation of damage or programmed ageing; major risk factor for human diseases
Lore & Background
Current ageing 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 ageing concept, whereby internal processes (epigenetic maintenance such as DNA methylation) inherently may cause ageing. Programmed ageing should not be confused with programmed cell death (apoptosis). Early life forms on Earth, starting at least 3.7 billion years ago, were single-celled organisms. Such organisms multiply by fission into daughter cells; thus single celled organisms have been thought to not age and to be potentially immortal under favourable conditions. However, evidence has been reported that aging leading to death occurs in the single-cell bacterium Escherichia coli and the yeast Saccharomyces cerevisiae.
Reader's Guide
Ageing is among the greatest known risk factors for most human diseases. In industrialized nations, the proportion of deaths from age-related causes reaches 90%. Characteristic signs include wrinkles, presbyopia, hair greying, menopause, hearing loss, frailty, and dementia. Dementia becomes more common with age: about 3% of people between 65 and 74, 19% of those between 75 and 84, and nearly half of those over 85 have dementia. Even within mortal species, there are cells with potential for immortality: cancer cells such as the HeLa cell line, and specific stem cells. Normal human cells die after about 50 cell divisions in laboratory culture (the Hayflick limit).
Did You Know?
- Normal human cells die after about 50 cell divisions in laboratory culture, known as the Hayflick limit.
- Evidence of aging has been reported in the single-cell bacterium Escherichia coli.
Frequently Asked Questions
What is Ageing?
Ageing is the lifelong, progressive accumulation of biological, psychological, and social changes that make an organism older. It is most prominently observed in humans, many animals, and fungi.
What drives Ageing at the cellular level?
Two main hypotheses dominate the field: the damage-accumulation model, where molecular and cellular wear builds up over time, and the programmed-ageing model, where genetic timers trigger decline. Gerontologists generally believe both mechanisms contribute to the overall process.
Do all living things experience Ageing?
No. Bacteria, perennial plants, and some simple animals appear to be biologically immortal and do not show the typical functional decline we associate with growing old. Ageing is a feature primarily of complex multicellular organisms like humans, most animals, and fungi.
Why is Ageing the biggest risk factor for human disease?
As cells and tissues accumulate damage or follow a programmed decline pathway, the body's repair and regulatory systems become less effective. This makes advanced age the single strongest predictor of conditions ranging from cancer to cardiovascular and neurodegenerative diseases.
Which fields of study focus on Ageing?
Gerontology is the dedicated discipline that examines the biology, psychology, and social dimensions of growing older. It sits within the broader field of biology and draws heavily on genetics, medicine, and public health.
More in Physiology & Medicine 1-19
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record