Definitions  Mortality can be used to define biological ageing, which refers to an organism's increased rate of death as it progresses throughout its life cycle and increases its chronological age. Another possible way to define ageing is through functional definitions, of which there are two main types The first describes how varying types of deteriorative changes that accumulate in the life of a post-maturation organism can leave it vulnerable, leading to a decreased ability of the organism to survive. The second is a senescence-based definition; this describes age-related changes in an organism that increase its mortality rate over time by negatively affecting its vitality and functional performance. An important distinction to make is that biological ageing is not the same thing as the accumulation of diseases related to old age; disease is a blanket term used to describe a process within an organism that causes a decrease in its functional ability. A number of characteristic ageing 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. Wrinkles develop mainly due to photoageing , particularly affecting sun-exposed areas (face). After peaking in the mid-20s, female fertility declines. After age 30 the mass of human body is decreased until 70 years and then shows damping oscillations. Muscles have reduced capacity of responding to exercise or injury and loss of muscle mass and strength (sarcopenia) is common. VO2 max and maximum heart rate decline. Hand strength and mobility are decreased during the aging process. These things include, "hand and finger strength and ability to control submaximal pinch force and maintain a steady precision pinch posture, manual speed, and hand sensation" People over 35 years of age are at increasing risk for losing strength in the ciliary muscle of the eyes which leads to difficulty focusing on close objects, or presbyopia. Most people experience presbyopia by age 45–50. The cause is lens hardening by decreasing levels of alpha-crystallin, a process which may be sped up by higher temperatures. 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. Menopause typically occurs between 44 and 58 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. 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. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. Frailty, a syndrome of decreased strength, physical activity, physical performance and energy, affects 25\% of those over 85.Percentage derived from Table 2 in Fried et al. 2001 Atherosclerosis is classified as an ageing disease. It leads to cardiovascular disease (for example stroke and heart attack) which globally is the most common cause of death. Vessel ageing causes vascular remodeling and loss of arterial elasticity and as a result causes the stiffness of the vasculature. Recent evidence suggests that age-related risk of death plateaus after age 105. The maximum human lifespan is suggested to be 115 years. The oldest reliably recorded human was Jeanne Calment who died in 1997 at 122.
Definitions There are multiple ways to define ageing. Functional age measures age by capability and takes into account social, psychological, and physiological age. Chronological age is based on the calendar year, from an individual's birth date to death date. Mortality can be used to define biological ageing, an organism's increased rate of death as it progresses throughout its life cycle . The processes and performance decline and bodily structure changes typical to chronological age. Another way to define ageing is through two types of functional definitions: The first describes how varying types of deteriorative changes that accumulate in the life of a post-maturation organism can leave it vulnerable, leading to a decreased ability of the organism to survive. The second is a senescence-based definition; this describes age-related changes in an organism that increase its mortality rate over time by negatively affecting its vitality and functional performance. An important distinction to make is that biological ageing is not the same thing as the accumulation of diseases related to old age; disease is a blanket term used to describe a process within an organism that causes a decrease in its functional ability. A number of characteristic ageing 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. Wrinkles develop mainly due to photoaging , particularly affecting sun-exposed areas (face). After peaking in the mid-20s, female fertility declines. After age 30 the mass of human body is decreased until 70 years and then shows damping oscillations. Muscles have reduced capacity of responding to exercise or injury and loss of muscle mass and strength (sarcopenia) is common. Maximum oxygen utilization and maximum heart rate decline. Hand strength and mobility are decreased during the aging process. These things include, "hand and finger strength and ability to control submaximal pinch force and maintain a steady precision pinch posture, manual speed, and hand sensation" People over 35 years of age are at increasing risk for losing strength in the ciliary muscle of the eyes which leads to difficulty focusing on close objects, or presbyopia. Most people experience presbyopia by age 45–50. The cause is lens hardening by decreasing levels of alpha-crystallin, a process which may be sped up by higher temperatures. 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. Menopause typically occurs between 44 and 58 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. 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. By age 80, more than half of all Americans either have a cataract or have had cataract surgery. Frailty, a syndrome of decreased strength, physical activity, physical performance and energy, affects 25\% of those over 85.Percentage derived from Table 2 in Fried et al. 2001 Atherosclerosis is classified as an ageing disease. It leads to cardiovascular disease (for example stroke and heart attack) which globally is the most common cause of death. Vessel ageing causes vascular remodeling and loss of arterial elasticity and as a result causes the stiffness of the vasculature. Recent evidence suggests that age-related risk of death plateaus after age 105. The maximum human lifespan is suggested to be 115 years. The oldest reliably recorded human was Jeanne Calment who died in 1997 at 122.
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There are multiple ways to define ageing. Functional age measures age by capability and takes into account social, psychological, and physiological age. Chronological age is based on the calendar year, from an individual's birth date to death date.
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