Sound Localization

Tests of sound localization indicate a decline in this ability with aging, beginning in the fourth decade (28). It is known that localization of low-frequency sounds depends on temporal discrimination (i.e., time of sound arrival) between the two ears, while in the high-frequency range, localization depends on discrimination of sound intensity between the two ears. Aging changes occur in both ears, but the rate of aging may be different in the two ears (122,130). Thus, deficits in localization...

Learning and Longevity

Learning has emerged as a factor in prolonging life and reducing disability and disease in old age (Box 2). Epidemiologic studies have reported that there is a positive correspondence between life expectancy and amount of schooling one receives (95,96). The benefit of education persists when active life expectancy or life free of disabilities is compared to total life expectancy or life with disabilities and this finding is irrespective of sex and race. As Katzman (97) quotes, Scholars grow...

Selective Longevity

The duration of life (longevity), the onset of aging, and the rate of mortality significantly differ among animal and plant species. In eukaryotes, the life span varies from a few days' duration in yeast cells (in Saccharomyces, mean chronological life span is 6 to 30-40 days, depending on environment and nutrients) to a duration of 5000 years in the California bristlecone pine (Pinus longaeva). In vertebrates, aging and death, assumed to occur in all species, were originally attributed to...

Info

Current concepts in the pathogenesis of age-related macular degeneration. Arch Ophthalmol 2004 122(4) 598-614. Review. 110. Kamei M, Hollyfield JG. TIMP-3 in Bruch's membrane changes during aging and in age-related macular degeneration. Invest Ophthalmol Vis Sci 1999 40(10) 2367-2375. 111. Plantner JJ, Jiang C, Smine A. Increase in interphotoreceptor matrix gelatinase A (MMP-2) associated with age-related macular degeneration. Exp Eye Res 1998 67(6) 637-645. 112. Bailey TA,...

Extrapolation of Mortality Trends

Demographers claim some expertise in predicting future mortality levels, and their method of choice is usually a mere extrapolation of past trends. Biologists and others sometimes criticize this approach because it seems to ignore underlying mechanisms. However, this critique is valid only insofar as such mechanisms are understood with sufficient precision to offer a legitimate alternative method of prediction. Although many components of human aging and mortality have been well described, our...

Anterior Chamber and Vitreous Gel Humor

The anterior chamber and its fluid, the aqueous humor, occupy a space between the cornea and the lens (Fig. 2B). The size and volume of the eye's anterior chamber decrease with age, mainly due to thickening of the lens. This growth occasionally exerts pressure on the canal of Schlemm (Fig. 2B), an outflow channel at the junction between the iris and the cornea, causing decreased flow and increased pressure intraocular pressure (IOP) of the aqueous humor. In normal aging, the increase in IOP is...

Changes in Balance and Falls

Balance or stable physical equilibrium can be studied clinically, as with gait, by simply observing individuals as they rise from a chair, stand, walk, or turn. Do the subjects examined sway, sweep, and stagger when performing these movements In the elderly, the fear of falling and pain, or limitation of joint movement, are all reflected in their carriage (21-24). The main adaptation to a balance disorder is the shortening of step length accompanied by slowing of gait and increasing of time...

Summary of Historical Trends

A compact summary of major trends in human longevity in industrialized countries is presented in Tables 3. Amidst the incredible detail available in historical mortality statistics, we cannot help but discern two major epochs before 1960 and after 1970. The driving trend in the former period was a rapid decline of mortality due to infectious disease, which had an impact across the age range but certainly a much larger effect at younger ages. The sharp reduction in infant and child mortality led...

Mortality Decline Among the Elderly

The most significant trend now affecting longevity in industrialized societies is the decline of death rates among the elderly. Until the late 1960s, death rates at older ages had declined slowly, if at all. Traditionally, rates of mortality decline were much higher at younger than at older ages. Since about 1970, however, there has been an aging of mortality decline, meaning that some of the most rapid declines in death rates are now occurring at older ages (23,24). Thus, the decade of the...

The Role of the Reticular Activating and the Limbic Systems

The reticular activating system, formed of an afferent and efferent network of interconnecting neurons distributed in the core midbrain, controls conscious alertness and, thus, makes sensory, motor, and visceral perception possible. Changes in sleep patterns with aging may be related to alterations in the level of alertness as manifested by the EEG changes discussed above and shifts in neurotransmitters, primarily serotonin (60,61) (Chapter 6). Serotonin appears to function as an inhibitory...

The Eyes Optical Components Cornea

Human Power

The cornea is the anterior portion of the eye, and its curved surface together with the watery layer of tears is responsible for most of the refraction of the light rays. During aging, the cornea becomes thicker and less curved, mainly due to an increase in the horizontal diameter of the eye. These changes alter the refractive properties of the cornea, leading to against the rule astigmatism, a condition characterized by defective corneal curvature and diffusion of light rays (8). The cornea is...

Aging Related Changes in the Retina

The human retina shows considerable age-related structural changes, particularly in its peripheral zones, although the macula and its fovea centralis are not spared. The aged retinal periphery is thinner (10-30 mm), containing a lesser number of rods and other nerve cell types. The aging-related loss of rods appears to be a slow process, beginning in the third and fourth decade, and may be related to accumulated damage due to physiological exposure to light (8-10). With aging rods, outer...

N Sleep EEG Changes with Aging

The EEG represents the background electrical activity of the brain as characterized by wave patterns of different frequencies a, 8 to 12 waves sec b, 18 to 30 waves sec 8,4 to 7 waves sec and 8, less than 4 waves sec. The a waves have the highest amplitude. With advancing age, the a rhythm (prominent in a person awake with eyes closed and mind at rest during the EEG test) slows throughout the brain as well as focally (temporal region). The b activity increases in aged persons. With respect to...

Death vs Immortality

While old age is approached gradually, without any specific physiologic markers of its onset, death is the terminal event that ends life. In broad terms, causes of death may be classified as trauma, accidents, and disease (Chapters 2 and 3). Trauma and accidents (e.g., high-speed vehicle crashes, dangerous occupations, drug abuse, cigarette smoking) are the major causes of death in young adulthood. Cancer, cardiovascular diseases, and metabolic diseases are the most frequent causes of death in...

Neurotransmission and Cell Communication

Information processing in the nervous system involves neurons talking to each other or with target cells. Research in neurotransmission, including neurotransmitter turnover, release, and binding to receptor is central to our understanding of CNS aging. Chemical transmission requires a series of events (Box 3). One of the most studied aspects of aging of the nervous system involves neurotransmitter changes at the synapse. In the healthy elderly, neurotransmitter levels and number, and the...

Maximum Individual Life Span

Limits to average life span, or life expectancy at birth, are one issue. When people discuss limits to the human life span, however, they often have another idea in mind the upper limit to an individual life span. Instead of asking how long we can live on average, we might ask how long one lucky individual can hope to live. This concept is actually much easier to understand than the notion of an upper limit to life expectancy. Who is the oldest person who has ever lived Even if we can never...

U References

Causes of death in Alzheimer's disease. Ann Epidemiol 1996 6(3) 195-200. 2. Baloh RW, Spain S, Socotch TM, et al. Posturography and balance problems in older people. J Am Geriatr Soc 1995 43(6) 638-644. 3. Alexander NB. Gait disorders in older adults. J Am Geriatr Soc 1996 44(4) 434-451. 4. Haibach PS, Slobounov SM, Slobounova ES, et al. Virtual time-to-contact of postural stability boundaries as a function of support surface compliance. Exp Brain Res 2007...

Rectangularization or Mortality Compression

The age pattern of human mortality can be characterized in various ways. Figure 4 shows the American mortality levels in 1900 and 1995 from three perspectives. The first panel shows death rates by age. These death rates are used to construct a life table, which describes the experience of a hypothetical cohort subject throughout its life to the death rates of a given year. Thus, the middle and last panels show the distribution of deaths and the proportion of survivors at each age among members...

Telomeres and Premature Aging

Among the first mouse models to show multiple signs of accelerated aging was the telomerase knockout mouse. These mice completely lack telomerase activity owing to a germ-line disruption in the gene encoding the essential telomerase RNA component, mTR (147). Interestingly, mTR- - mice are asymptomatic for the first three to four generations. Subsequent generations, however, are shorter lived and prematurely develop hair loss and graying, ulcerative skin lesions, delayed wound healing, reduced...

Optimism vs Pessimism

In recent years, the extrapolative approach to mortality prediction has been challenged by assertions that future changes in average human life span may come more or less quickly than in the past. The more optimistic view that life span will increase rapidly in the near future is partly a result of the acceleration in rates of mortality decline among the elderly in developed countries during the past few decades. From a historical perspective, however, this change is relatively recent and...

Contents

Preface iii Acknowledgments v Contributors ix 1. Old Age as a Stage of Life Common Terms Related to Aging and Methods Used to Study Aging 3 Paola S. Timiras 2. Human Longevity in Historical Perspective 11 John R. Wilmoth 3. Comparative Aging, Geriatric Functional Assessment, Aging and Disease 23 Paola S. Timiras 4. Cellular Senescence, Cell Death, and Transgenic Mouse Models of Aging 41 Judith Campisi 5. Theories of Life Span and Aging 55 Part II Systemic and Organismic Aging 6. The Nervous...

Lewy and Hirano Bodies

The Lewy and Hirano bodies are eosinophilic, cytoplasmic inclusions, derived from the differential expression of particular proteins responsible for selective neuronal vulnerability (51). Lewy bodies are usually spheroid in shape with a dense central core (Fig. 7), and the Hirano bodies may often appear as spindle shaped and fusiform. Lewy bodies may be present in aged individuals (60 years of age and older) without clinical evidence of PD, but are more numerous in those individuals affected by...

Differential Timetables of Aging in Organs and Systems

Changes with aging lack uniformity, not only among individuals of the same species but also within the same individual onset, FIGURE 5 Successful or healthy aging. Successful aging is based on maintenance of mental and physical function, avoidance of diseases, and enjoyment of life. rate, and magnitude of changes vary depending on the cell, tissue, organ, system, or laboratory value considered (28). A number of laboratory values, many of which often may remain unchanged with aging, or may...

Neurofibrillary Tangles NFTs and Neuritic Plaques NPs

Neurofibrillary Tangles

NFTs consist of intracellular tangled masses of fibrous elements, often in flame-shaped bundles, coursing the entire cell body FIGURE 6 (A) A neuron from the cerebral cortex of a 605-day-old male Long-Evans rat (50). There are numerous dense bodies (lipofuscin) irregularly distributed in the perikaryon (original magnification x1440) (B) a portion of a neuron from the cerebral cortex of the same 605-day-aged animal (50). The lipofuscin granules are clustered at one pole of the nucleus (original...

Prehistoric and Preindustrial Eras

We do not know much about how long humans lived before 1750. Around that time, the first national population data were collected for Sweden and Finland. For earlier eras, we have some life tables constructed for municipal populations, members of the nobility, and other groups that were probably not representative of the national population at large (11,12). After aThe National Health Interview Survey began in 1957 and contains information on health status from individual self-evaluations. The...

Iris and Senile Miosis

The iris is a smooth muscular ring forming the pupil of the eye Fig. 2B . Contraction and dilation of the pupil during the light reflex changes the amount of light entering the eye and is also important in the accommodation reflex. In the elderly, the iris appears paler in the middle, mainly due to loss of pigmentation in the radial dilator muscles. With aging, there is a mild but constant increase in the density of collagen fibers in the iris stroma and noncellular perivascular zones. A...

Down Syndrome

Down syndrome mongolism is another example characterized by several symptoms, including accelerated aging and premature death, and is due to trisomy at chromosome 21. The incidence of the syndrome is greatest among children born from mothers 40 years of age and older, and the genetic abnormality has, therefore, been related to aging processes involving the oocytes Chapter 10 . Although in 20 to 30 of cases, the extra chromosome is contributed by the father, paternal age does not seem to have...

Pharmacological Strategies

Neurosurgery was the first therapeutic approach to parkinsonism. Replacement by L-DOPA of the lost striatal DA adopted in the early 1960s was welcomed as a safer alternative to surgery. In the neuronal pathway of catecholamine biosynthesis, the enzyme tyrosine hydroxylase catalyzes the conversion of the amino acid tyrosine to dihydroxyphenylalanine L-dopa, levodopa , which is then converted to DA by the action of dopa-decarboxylase. L-Dopa, unlike DA, can pass the BBB see below , and when...

Types of Presbycusis

Ear Loss About Men

Presbycusis may occur due to damage to different parts of the auditory systems. Based on the source of damage, four types of presbycusis are recognized sensory, neural, metabolic or strial , and cochlear conductive 123,130 . The onset of presbycusis may be any time from the third to sixth decade of life, depending on type. Individuals suffering from these disturbances show distinct and differing audiograms Fig. 8 , which are clinically used to diagnose types of impairment. More complicated...