**Ageing Process and Symptoms**:
– Human beings, animals, and fungi age and die.
– Teenagers lose the ability to hear high-frequency sounds.
– Wrinkles develop mainly due to photoageing.
– Hair turns grey around age 50.
– Cataracts and frailty become more common with age.
– Maximum oxygen use and heart rate decline with age.
– Hand strength and mobility decrease.
– Vessel ageing causes arterial stiffness.
– Risk of death plateaus after age 105.
**Mental Changes and Biological Basis**:
– Dementia becomes more common with age.
– Memory decline varies with different types of memory.
– Intelligence declines with age, with individual variations.
– Changes to the brain include a reduction in myelinated axons.
– Visual impairment can result from ageing.
– Ageing is a risk factor for most human diseases.
– Nearly 100,000 people globally die daily from age-related causes.
– Factors influencing ageing include programmed and error-related factors.
– Genetic mutations and environmental events contribute to ageing.
**Biological Mechanisms and Molecular Hallmarks of Ageing**:
– Genomic instability and mutations affect ageing.
– Telomere attrition plays a role in cellular ageing.
– Epigenetic alterations impact gene expression and ageing.
– Loss of proteostasis and deregulated nutrient sensing contribute to ageing.
– Mitochondrial dysfunction and cellular senescence are hallmarks of ageing.
– FOXO3/Sirtuin pathway and caloric restriction influence ageing.
– Growth hormone/Insulin-like growth factor 1 pathway affects ageing.
– Mitochondrial electron transport chain activity plays a role in ageing.
**Factors Influencing Longevity and Immortality**:
– Bacteria, strawberry plants, and Hydra are potentially immortal.
– Single-celled organisms do not age and are potentially immortal.
– Sexual reproduction enabled ageing and mortality in organisms.
– Cancer cells and certain stem cells have potential immortality.
– Some perennial plants are potentially immortal through vegetative reproduction.
– Certain species exhibit negligible senescence.
– Genetic studies of human centenarians show a genetic aspect to ageing.
– Immortality and lifespan variation exist in diverse organisms on Earth.
**Research, Diet, and Mitochondrial Theories**:
– Life extension research is related to ageing studies.
– Mediterranean diet is associated with lower heart disease risk.
– Higher consumption of specific food groups reduces mortality risk.
– Insufficient clinical evidence on dietary practices affecting ageing as of 2021.
– Exercise is linked to lower mortality rates in physically active individuals.
– Free radicals from mitochondrial activity damage cellular components.
– Caloric restriction reduces DNA damage in ageing rats and mice.
– Oxidative DNA damage reduction is linked to slower ageing and increased lifespan.
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. Reaction time, for example, may slow with age, while memories and general knowledge typically increase. Ageing is associated with increased risk of cancer, Alzheimer's disease, diabetes, cardiovascular disease and many more. Of the roughly 150,000 people who die each day across the globe, about two-thirds die from age-related causes.
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 the internal processes (epigenetic maintenance such as DNA methylation) inherently may cause ageing. Programmed ageing should not be confused with programmed cell death (apoptosis).
Obesity has been proposed to accelerate ageing, whereas dietary calorie restriction in non-primate animals slows ageing while maintaining good health and body functions. In primates (including humans), such life-extending effects remain uncertain.