Aging definitions - Balcombe and Sinclair

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Health Sciences
Health Sciences 2711A/B
Aleksandra Zecevic

Aging: definitions, mechanisms and the magnitude of the problem Introduction • two fundamental parameters for aging o maximum lifespan o expectation of life or average lifespan • these parameters can only be studied in populations not individuals • maximum lifespan in animal species is seen only in controlled constant environments, like laboratories • aging and senescence are often used interchangeably – both are progressive changes in the tissues or organs of the body leading to a decline in function and death o features associated with aging include: loss of skin elasticity, decline in muscular strength, loss of hair, decline in immune competence o most of these features occur after reproductive ability has ceased o specifically, senescence refers to the period after reproductive activity and is associated with degenerative changes related to the passage of time o aging refers to any time related process and could begin at any time, for example it could begin at conception Definitions of aging • biologists define aging as a continuous process that starts at conception and continues until death • in humans there are landmarks that help divide the process into various stages o no clear landmarks exist, while four or five decades of life are well defined the process of aging lacks a clear definition • chronological age o currently the most popular method o passage of time from birth onwards o with passage of time there is an increased incidence of physical, mental and functional problems o the question of what age is “old” arises and used for things like retirement cut off– what is old now is later than in previous times • biological age o pathological model o presence or absence of physical disease, function or cognitive impairment o increased incidence of chronic disease later in life o old age is characterized by physical illness, poor nutrition, inadequate housing o Sheldon identified diseases attributable to old age which lead to the theory that the development of these diseases was normal to the process of aging  diseases like CVD, stroke and dementia are common today o suggested that normal aging should be  universal  degenerative  progressive  intrinsic • sociological age o with increased age comes altered roles in society o these roles depend on how the culture views old age and what is normal behaviour for someone in old age o going to a nightclub is considered behaviour done by young people, if a 70 year old went to a nightclub they would be considered young by their behaviour and its attached social meaning • successful and unsuccessful aging o Cicero 44BC – “old age is not a phase of decline and loss, but instead, harbours the opportunity for positive change and productive functioning” o While many theories today focus on decline and loss there is evidence to support Cicero’s theory, like…  there is much variability in aging  older people can still learn supporting that aging can be associated with new development  however the ability to learn new things diminishes with age, balances the loss of previous information with the gain of new information, this balance is offset the older you get o Social and psychological theories focus on the interplay of gains and losses between individuals and society o The medical model focuses on successful aging as adding life to your years and not years to your life. It would be detrimental to live longer but suffering from a chronic disease. Relies on a dynamic interaction b/w LE and the age of onset of a chronic illness or disability, to be successful there must be a compression of morbidity Theories of aging • cellular theories o programmed cell death  study of aging at the cellular level through transplant experiments and vitro cell cultures • sk
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