Old age
Main article: Old age
The World Health Organization finds "no general agreement on the age at which a person becomes old." Most "developed countries" set the age as 60 or 65. However, in developing countries inability to make "active contribution" to society, not chronological age, marks the beginning of old age.[80] According to Erikson's stages of psychosocial development,
old age is the stage in which individuals assess the quality of their
lives. In reflecting on their lives, people in this age group develop a
feeling of integrity if deciding that their lives were successful or a
feeling of despair if evaluation of one's life indicates a failure to
achieve goals.[81]
Physically, older people experience a decline in muscular strength,
reaction time, stamina, hearing, distance perception, and the sense of
smell.[82] They also are more susceptible to diseases such as cancer and pneumonia due to a weakened immune system.[83]
Programs aimed at balance, muscle strength, and mobility have been
shown to reduce disability among mildly (but not more severely) disabled
elderly.[84]
Sexual expression depends in large part upon the emotional and
physical health of the individual. Many older adults continue to be
sexually active and satisfied with their sexual activity.[85]
Mental disintegration may also occur, leading to dementia or ailments such as Alzheimer's disease. It is generally believed that crystallized intelligence increases up to old age, while fluid intelligence decreases with age.[86] Whether or not normal intelligence increases or decreases with age depends on the measure and study. Longitudinal studies show that perceptual speed, inductive reasoning, and spatial orientation decline.[87] An article on adult cognitive development reports that cross-sectional studies show that "some abilities remained stable into early old age."[88]
Immunity & Aging
In the recent decades, there has been an increase in the aging
population across the world coupled with declining birth rates and an
increased lifespan of individuals. The proportion of the elderly in
developing and less developed countries is also expected to increase.
According to the WHO, the proportion of old individuals (over the age of
60 years) will rise to 22% of the world population.[101]
In light of this, it is becoming critical to improve our understanding
of aging and its associated diseases to support existing healthcare
systems coping with the burden of diseases and to promote healthy aging.
Diseases are a concern for the aging population as the recovery is
longer, and most of the time incomplete, often leading to
hospitalization, complication, integration in specialized care centers
and ultimately death. The higher incidence of infectious diseases (e.g.,
pneumonia and influenza), autoimmunity (e.g., rheumatoid arthritis),
cancer (e.g., prostate and lung), Type 2 diabetes and cardiovascular
diseases is an obvious issue for the elderly. The link between these
diseases is immunity, and loss of immune functions may explain the
age-associated incidence of such diseases by reduced immunosurveillance,
polyfunctionality or regulation.
The name 'immunosenescence' has been used to describe loss of
immune functions in elderly individuals (>65 years old). Although the
mechanisms leading to immunosenescence are not clear, it has been
associated with increased susceptibility to diseases, infections and
poor response to treatments and vaccination.[1]
With advancing age, antigen-specific immunity is eroded partly due to
alterations in the innate immunity. The changes affecting the immune
system are leading to global dysfunctions. Although immunosenescence is
characterized by changes in both the innate and adaptive arms of the
immune system,[2]
the important contributor to decline in immune function in the elderly
is the changes observed in adaptive immunity, including T and B
lymphocytes. Antigen encounter normally induces an immune response to
eliminate the invader by the concerted T- and B-cell responses, which
enables a faster and stronger response following secondary encounter
(immune memory).
With aging, the ability to maintain receptor diversity reduces,[3] and this is paralleled by the reduction in the number of naive T cells in the periphery.[4]
One hypothesis put forward to explain this phenomenon is the involution
of the thymus, where T-cell maturation happens (Figure 1). Thymic
involution is not only observed in the elderly, but begins much earlier
in life, after puberty. With age, the number and frequency of
circulating naive T cells (CD45RA+CCR7+CD28+CD27+)
is reduced, and this is associated to reduced thymopoiesis, as well as
increased number of memory cells due to pathogens encountered during the
course of life.[5]
Another hypothesis to, at least partly, explain immunosenescence is the
telomere length. Telomeric repeats (TTAGGG) are present at the end of
chromosomes and serve to protect DNA from alterations (Figure 1). An
intense replicative history will thus induce a shortening of telomeres,
which put these cells at risk for DNA mismatch.[6] Thus, telomere shortening has been primarily identified in highly differentiated effector memory CD8+ T cells, most of which are CD28− T cells.[7]
As loss of telomeric repeats is associated with loss of proliferative
capacity, telomeres have been associated to replicative senescence. It
is of note that despite this, evidence shows that telomere length is not
the shortest in the highly differentiated T cells,[8] suggesting a more complex relationship between telomeres and senescence.
"Polyfunctionality Mampus" adalah Pelaku Pembunuhan Munir..."POLYCARPUS"
"PILOT"...karena Mereka semua "DRIVE" DIA (Polisi yang Menangani KES PEMBUNUHAN MUNIR,yang ga terselesaikan....sampai sekarang....karena MEREKA semua GADUNGAN)
Comments