Basic of Geriatrics and Internal Medicine for Physiotherapist by Rasheedy D - HTML preview

Ageing Process

Definition of ageing:

Physiological ageing (normal ageing): is a complex process of progressive reduction in the function of all body organs. This process may be summarized in the expression “homeostenosis”. It reflects alteration of organ structure and function with time alone and in the absence of supervening disease processes.

Physiological ageing is an inevitable changes can be explained from both biologic and psychosocial perspectives.

Processes influencing ageing include gene variations and differences in expression and environmental factors.

Age and disease are closely associated phenomena. Secondary ageing then refers to those aspects of the aged state that are attributable to disease.

Fig 1: Predictors of the Ageing process

Characters of the ageing process:

Aging is characterized by being Universal, Cumulative, Unidirectional, Heterogeneity, Intrinsic, and Deleterious.

Ageing is different from Cellular senescence is the process by which a cell loses its ability to divide, grow, and function, ultimately leading to cell death.

Theories of ageing (biological)

Fig 2: examples of biological theories of ageing

Cellular senescence/ telomere theory:

Replicative senescence is a specific type of cellular senescence that ultimately results from loss of telomeres (specialized structures composed of a repeating DNA sequence and located at the ends of each linear chromosome).With each cell division, a small amount of DNA is lost at each chromosome end, resulting in shorter telomeres, altered telomere structure, and eventual replicative senescence.

Activation of the telomerase enzyme will regenerate telomeres, prevent replicative senescence, and immortalize human primary cell cultures

Free Radical theory:

Free radicals are reactive oxygen species (ROS) are highly reactive molecules that can damage all sorts of cellular components.

ROS can originate from exogenous sources such as ultraviolet (UV) and ionizing radiations or from several intracellular sources: (phagocytosis, fatty acid degradation, drug detoxification by liver, ATP utilization).

Toxic accumulation of ROS interfere with cell communication, disturb DNA, RNA and protein synthesis, lower energy levels and generally impede vital chemical processes.

To protect against oxidation there are many different types of antioxidants, from vitamins C and E selenium, CoQ10 and lipoic acid to enzymes such as superoxide dismutase (SOD), catalase, and glutathione peroxidase. Briefly, antioxidant enzymes are capable of degrading ROS into inert compounds through a series of chemical reactions.

The Neuro-endocrine Theory

Hypothalamo-pituitary-adrenal (HPA) axis is the master regulator that control the onset and termination of each life stage. It is also responsible for the maintenance of the internal “homeostasis” (steady state) despite the continuing changes in the environment.

During life span, chronic exposure to severe stress from a multitude of physical, biological, or emotional stimuli may exhaust or weaken the capacity to adapt and lead to the so-called “diseases of adaptation” and death . Aging would then result from “a decreasing ability to survive stress.

Evidence to this theory: the cortisol hormone which is considered to be responsible for stress is one of the few hormones that increases with age.

The immunosenescence theory:

The immune system must control and eliminate foreign organisms and substances in the host body while at the same time recognizing and therefore sparing from destruction the molecules (cells and tissues) from oneself. In most elderly humans, immunosenescence is characterized by a decreased resistance to infectious diseases, a decreased protection against cancer, and an increased failure to recognize self (hence, autoimmune pathology.

The disposable soma

The somatic cells are only preserved to maintain reproductive functions. After reproduction somatic cells become disposable.

Antagonistic pleiotropy

The theory of antagonistic pleiotropy is based on two assumptions. First, it is assumed that a particular gene may have an effect not on one trait only but on several traits of an organism (pleiotropy). The second assumption is that these pleiotropic effects may affect individual fitness in opposite (antagonistic) ways.

Such genes will be maintained in the population due to their positive effect on reproduction at young ages despite their negative effects at old age (their negative effects in later life will look exactly like the aging process)

Error catastrophe

Gene expression accuracy diminishes with age. This culminates in a higher proportion of abnormal proteins.

There is a certain rate of error tolerance of a cell, exceeding which the cell fails in its ability to sustain and function normally.

Thus, accumulation of errors in the genomic replication machinery beyond a certain threshold might lead to erroneous dysregulation of the protein synthesis, folding and expression mechanisms which ultimately might bring about deterioration in the functionality of the cell.

Types of Ageing:

The elderly are special population with special needs:

Physiological Changes in the Elderly (Normal Aging is not a disease)

Multiple comorbidities and multiple medications: The incidence of chronic diseases increases with ageing e.g. dementia, Parkinsonism, stroke, heart diseases leading to polypharmacy.

Overlapping Variables (physiological, social, psychological, environmental variables) &multiple diseases): heterogeneous Population: Need for Individualized Treatment:

Atypical presentations of diseases

They need different assessment approach (see comprehensive geriatric assessment) through Multidimensional, Interdisciplinary, Geriatric team

The goal of elderly care is maintaining function &quality of life:" To add life to years NOT only years to life

Age related physiological changes:

Aging and disease are not synonymous. Although the aging process makes individuals more vulnerable to illness and disease, pathology is not inevitable with age. Aging alone generally does not cause symptoms.

The major age-related biologic change is a diminished reserve capacity and the inability to maintain homeostasis in the face of stressors such as a disease or adverse environmental factors such as excessive heat.