Ageing

agingageoctogenariantwentysomethingseptuagenarianagedaging processsexagenariansuccessful agingthirtysomething
Ageing or aging (see spelling differences) is the process of becoming older.wikipedia
1,064 Related Articles

Population ageing

aging populationageing populationpopulation aging
In the broader sense, ageing can refer to single cells within an organism which have ceased dividing (cellular senescence) or to the population of a species (population ageing).
Population ageing is an increasing median age in the population of a region due to declining fertility rates and/or rising life expectancy.

DNA methylation

methylationmethylatedhypermethylation
The causes of ageing are uncertain; 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 ageing concept, whereby internal processes (such as DNA methylation) may cause ageing.
In mammals DNA methylation is essential for normal development and is associated with a number of key processes including genomic imprinting, X-chromosome inactivation, repression of transposable elements, aging, and carcinogenesis.

Senescence

senescentagingage
In the broader sense, ageing can refer to single cells within an organism which have ceased dividing (cellular senescence) or to the population of a species (population ageing).
Aging is characterized by the declining ability to respond to stress, increased homeostatic imbalance, and increased risk of aging-associated diseases including cancer and heart disease.

Aging-associated diseases

age-related diseaseaging-associated diseaseage-associated disease
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 die from age-related causes.
Age-associated diseases are to be distinguished from the aging process itself because all adult animals age, save for a few rare exceptions, but not all adult animals experience all age-associated diseases.

Dementia

senilesenilitysenile dementia
Dementia becomes more common with age.
A dementia diagnosis requires a change from a person's usual mental functioning and a greater decline than one would expect due to aging.

Memory and aging

cognitive gerontologymemoryage-related
Furthermore, many types of memory decline with ageing, but not semantic memory or general knowledge such as vocabulary definitions, which typically increases or remains steady until late adulthood (see Ageing brain).
Age-related memory loss, sometimes described as "normal aging", is qualitatively different from memory loss associated with dementias such as Alzheimer's disease, and is believed to have a different brain mechanism.

Alzheimer's disease

AlzheimerAlzheimer’sAlzheimer’s disease
The spectrum ranges from mild cognitive impairment to the neurodegenerative diseases of Alzheimer's disease, cerebrovascular disease, Parkinson's disease and Lou Gehrig's disease.
The first symptoms are often mistakenly attributed to ageing or stress.

Presbyopia

presbyopicnear pointneeds glasses to read
People over 35 years of age 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 -crystallin, a process which may be sped up by higher temperatures.
Presbyopia is a condition associated with the aging of the eye that results in progressively worsening ability to focus clearly on close objects.

Photoaging

skin agingaccelerated aging of the skinphoto-aging
Wrinkles develop mainly due to photoageing, particularly affecting sun-exposed areas (face).
The deterioration of biological functions and ability to manage metabolic stress is one of the major consequences of the aging process.

Wrinkle

wrinklescrow's feetwrinkling
Wrinkles develop mainly due to photoageing, particularly affecting sun-exposed areas (face).
Skin wrinkles typically appear as a result of aging processes such as glycation, habitual sleeping positions, loss of body mass, or temporarily, as the result of prolonged immersion in water.

Hearing loss

deafdeafnesshearing impairment
Almost half of people older than 75 have hearing loss (presbycusis) inhibiting spoken communication. Many vertebrates such as fish, birds and amphibians do not suffer presbycusis in old age as they are able to regenerate their cochlear sensory cells, whereas mammals including humans have genetically lost this ability.
Hearing loss may be caused by a number of factors, including: genetics, ageing, exposure to noise, some infections, birth complications, trauma to the ear, and certain medications or toxins.

Age and female fertility

biological clockincreased female agebiological clocks
After peaking in the mid-20s, female fertility declines.
Female fertility is affected by age.

Human hair color

hair colorhair colourgray hair
Around age 50, hair turns grey. Pattern hair loss by the age of 50 affects about 30–50% of males and a quarter of females.
Particular hair colors are often associated with ethnic groups, while gray or white hair is associated with age.

Frailty syndrome

frailtymedically frailFrail elderly
Frailty, defined as loss of muscle mass and mobility, affects 25% of those over 85.
Frailty is a condition associated with ageing, and it has been recognized for centuries.

Cataract

cataractscongenital cataractsjuvenile cataract
By age 80, more than half of all Americans either have a cataract or have had cataract surgery.
Cataracts become more common with age.

Sirtuin

sirtuinssirt4
deregulated nutrient sensing (relating to the Growth hormone/Insulin-like growth factor 1 signalling pathway, which is the most conserved ageing-controlling pathway in evolution and among its targets are the FOXO3/Sirtuin transcription factors and the mTOR complexes, probably responsive to caloric restriction)
Sirtuins have been implicated in influencing a wide range of cellular processes like aging, transcription, apoptosis, inflammation and stress resistance, as well as energy efficiency and alertness during low-calorie situations.

Proteostasis

protein homeostasisprotein quality control network
loss of proteostasis (protein folding and proteolysis)
Cellular proteostasis is key to ensuring successful development, healthy aging, resistance to environmental stresses, and to minimize homeostasis perturbations by pathogens such as viruses.

Psychology

psychologicalpsychologistpsychologists
In humans, ageing represents the accumulation of changes in a human being over time, encompassing physical, psychological, and social changes.
In addition to studying children, developmental psychologists also study aging and processes throughout the life span, especially at other times of rapid change (such as adolescence and old age).

Reproductive-cell cycle theory

The reproductive-cell cycle theory argues that ageing is regulated specifically by reproductive hormones that act in an antagonistic pleiotropic manner via cell cycle signalling, promoting growth and development early in life to achieve reproduction, but becoming dysregulated later in life, driving senescence (dyosis) in a futile attempt to maintain reproductive ability. The endocrine dyscrasia that follows the loss of follicles with menopause, and the loss of Leydig and Sertoli cells during andropause, drive aberrant cell cycle signalling that leads to cell death and dysfunction, tissue dysfunction (disease) and ultimately death. Moreover, the hormones that regulate reproduction also regulate cellular metabolism, explaining the increases in fat deposition during pregnancy through to the deposition of centralised adiposity with the dysregulation of the HPG axis following menopause and during andropause (Atwood and Bowen, 2006). This theory, which introduced a new definition of ageing, has facilitated the conceptualisation of why and how ageing occurs at the evolutionary, physiological and molecular levels.
Rather than seeing aging as a loss of functionality as we get older, this theory defines aging as any change in an organism over time, as evidenced by the fact that if all chemical reactions in the body were stopped, no change, and thus no aging, would occur.

DNA damage theory of aging

DNA damagecumulative age-related cellular alterationsdamage DNA
DNA damage theory of ageing: DNA damage is thought to be the common basis of both cancer and ageing, and it has been argued that intrinsic causes of DNA damage are the most important drivers of ageing. Genetic damage (aberrant structural alterations of the DNA), mutations (changes in the DNA sequence), and epimutations (methylation of gene promoter regions or alterations of the DNA scaffolding which regulate gene expression), can cause abnormal gene expression. DNA damage causes the cells to stop dividing or induces apoptosis, often affecting stem cell pools and hence hindering regeneration. However, lifelong studies of mice suggest that most mutations happen during embryonic and childhood development, when cells divide often, as each cell division is a chance for errors in DNA replication.
The DNA damage theory of aging proposes that aging is a consequence of unrepaired accumulation of naturally occurring DNA damages.

Calorie restriction

caloric restrictionlow calorielow-calorie
deregulated nutrient sensing (relating to the Growth hormone/Insulin-like growth factor 1 signalling pathway, which is the most conserved ageing-controlling pathway in evolution and among its targets are the FOXO3/Sirtuin transcription factors and the mTOR complexes, probably responsive to caloric restriction) The discovery, in 1934, that calorie restriction can extend lifespan by 50% in rats has motivated research into delaying and preventing ageing.
Long-term caloric restriction at a level sufficient for slowing the aging process is generally not recommended in children, adolescents, and young adults (under the age of approximately 21), because this type of diet may interfere with natural physical growth, as has been observed in laboratory animals.

Human body

bodyhuman anatomyhuman physiology
In humans, ageing represents the accumulation of changes in a human being over time, encompassing physical, psychological, and social changes.
Development and growth continue throughout life, through childhood, adolescence, and through adulthood to senility, and are referred to as the process of ageing.

Free-radical theory of aging

free radical theory of agingfree-radical theoryfree radical theory
Free-radical theory: Damage by free radicals, or more generally reactive oxygen species or oxidative stress, create damage that may give rise to the symptoms we recognise as ageing. Michael Ristow's group has provided evidence that the effect of calorie restriction may be due to increased formation of free radicals within the mitochondria, causing a secondary induction of increased antioxidant defence capacity.
The free radical theory of aging (FRTA) states that organisms age because cells accumulate free radical damage over time.

Michael Ristow

Ristow, Michael
Free-radical theory: Damage by free radicals, or more generally reactive oxygen species or oxidative stress, create damage that may give rise to the symptoms we recognise as ageing. Michael Ristow's group has provided evidence that the effect of calorie restriction may be due to increased formation of free radicals within the mitochondria, causing a secondary induction of increased antioxidant defence capacity.
Michael Ristow (b April 24, 1967) is a German medical researcher who has published influential articles on biochemical aspects of mitochondrial metabolism and particularly the possibly health-promoting role of reactive oxygen species in diseases like type 2 diabetes, obesity and cancer, as well as general aging due to a process called mitohormesis.

Caenorhabditis elegans

C. eleganswormsC.elegans
A model organism for studying of ageing is the nematode C. elegans, thanks to its short lifespan of 2–3 weeks, our ability to easily perform genetic manipulations or to suppress gene activity with RNA interference, or other factors.
C. elegans has been a model organism for research into ageing; for example, the inhibition of an insulin-like growth factor signaling pathway has been shown to increase adult lifespan threefold; while glucose feeding promotes oxidative stress and reduce adult lifespan by a half.