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At least 1,513 records · Page 84Linked to original sources
PubMed2002

Fitness versus longevity in age-structured population dynamics.

We examine the dynamics of an age-structured population model in which the life expectancy of an offspring may be mutated with respect to that of the parent. While the total population of the system always reaches a steady state, the fitness and age characteristics exhibit counter-intuitive behavior as a function of the mutational bias. By analytical and numerical study of the underlying rate equations, we show that if deleterious mutations are favored, the average fitness of the population reaches a steady state, while the average population age is a decreasing function of the average fitness. When advantageous mutations are favored, the average population fitness grows linearly with time t, while the average age is independent of the average fitness. For no mutational bias, the average fitness grows as t2/3.

Life Expectancy↗
PubMed2000

[Aging, activity and longevity].

From its origin to its death the human organism is submitted to functional, material, and morphological changes that are perceptible. These changes permit classifying an individual as young, adult, old, active or infirm. But this estimation is not always correct. Some appear younger, some older than expected from their chronological age. But what is aging and how can it be measured? For this, so-called markers or biological markers of aging are used which are measurable indicators of aging in live organisms. A description of the complexity, the asynchronous course, and the biological variety and variability of biological age is less successful with a single indicator than with the inclusion of several markers in a multi-factorial measuring system, in a so-called test battery. Various test batteries have already been applied in numerous studies that consist of biochemical scans, mental and also social parameters in different combinations. A more precise description of such a test battery can be seen in the following example of a discussion of the ILSE study.

Activities of Daily Living↗
PubMed2001

[Knowledge for prolonging longevity without disability].

The relationship between quality of life and aging is difficult to describe with the usual epidemiological concepts like mortality. A functional approach is more important and meaningful for the analysis of the aging process. The ICIDH classification has the advantage of combining the diseases process itself and the consequences concerning functional limitations. Studies about the "active life expectancy" show that quality of life and life expectancy are two different dimensions of the aging process. For the purpose of prevention, it is important to demonstrate that preventive interventions could help reduce the number of years with functional limitations. Most of the epidemiological studies indicate that even lost functions could be restored. For these interventions, it is important to individualize the goals for preventive measures to balance physical and emotional needs of the elderly.

Aged↗
PubMed2004

Economic growth, longevity and the epidemiological transition.

This paper integrates investments in health to a standard growth model where physical and human capital investments are the combined engines of growth. It shows the existence of two distinct health regimes separated by an "epidemiological transition." The various patterns of this transition identified in the epidemiological literature can be mapped into the model. The model also leads to the important hypothesis that the epidemiological transition may induce an economy to switch to a modern growth regime.

Economics↗
PubMed2005

Evolution of human longevity, population pressure and the origins of warfare.

In a protected environment, humans have the longest lifespan of all primates. However, during the emergence of Homo sapiens from pre-hominids, the expectation of life at birth would have been quite low. On the basis of reasonable assumptions, an average expectation of life of less than 20 years is sufficient to maintain a population of hunter-gatherers. As individuals became better adapted to their environment, the mortality rate would gradually decrease, and this would result in the survival of more offspring to adulthood. Thus, the population will increase, and one of the consequences in human evolution is the migration of human communities to many new habitats. The development of agriculture provided a more reliable source of food, and stimulated further the increase in population size. Villages became towns, and then cities, states and empires arose which had very large populations, and competed for land and other resources. Armies were raised and were often at war. All this was due to population pressure, as Malthus had realised more than 200 years ago. However, neither he, nor any of the others who discussed warfare, understood that the demographic changes that produced large human populations was a steady increase in the expectation of life at birth. This inevitably occurred at the same time as man gradually gained more control over his environment, and achieved far more reproductive success than is seen in hunter-gatherers living in a harsh, stressful environment.

Agriculture↗
PubMed2006

Caloric restriction does not enhance longevity in all species and is unlikely to do so in humans.

Calorie restriction is known to increase lifespan in many but not all species and may perhaps not do so in humans. Exceptions to life extension have been identified in the laboratory and others are known in nature. Given the variety of physiological responses to variation in food supply that are possible, evolutionary life history theory indicates that an increased investment in maintenance in response to resource shortage will not always be the strategy that maximises Darwinian fitness. Additionally, for the well-studied species in which life extension is observed, there is considerable variation in the response. This suggests that it is not an ancient ancestral response, which has been conserved across the species range. Although calorie restriction does not increase lifespan in all species, it remains a fascinating and valuable tool to study ageing at the whole organism level.

Aging↗
PubMed2006

Caloric restriction and human longevity: what can we learn from the Okinawans?

Caloric (or dietary) restriction (CR) extends lifespan and lowers risk for age associated diseases in a phylogenetically diverse group of species. Whether prolonged CR increases average or maximum lifespan or promotes a more youthful physiology in humans at advanced ages is not yet known. However, available epidemiological evidence indicates that CR may already have contributed to an extension of average and maximum life span in one human population and appears to have lowered risk for age associated chronic diseases in other human populations. We review the human studies in the context of a special human population, older Okinawans, who appear to have undergone a mild form of prolonged CR for about half their adult lives.

Aging↗
PubMed2006

Food, fertility and longevity.

Some animals live in environments in which the food supply fluctuates. When it is scarce these animals do not breed, but invest resources into survival until food is again available, and they can reproduce. Under these circumstances the lifespan can be increased, just as it is after calorie restriction. Other animals have a fairly constant food supply, and it is predicted that these would not have an extended life span if subjected to calorie restriction. Hibernation is a natural form of calorie restriction, and in some cases may lengthen lifespan.

Adaptation, Physiological↗
PubMed2006

Energetic efficiency under stress underlies positive genetic correlations between longevity and other fitness traits in natural populations.

Evolutionary relationships among fitness traits are considered in terms of the near-to-universal scenario of stressful environments leading to a resource-deficient and hence energy-deficient world. Fitness approximates to energetic (and metabolic) efficiency under this environmental model. When fitness is high, stress resistance (reducible to oxidative-stress resistance) and metabolic stability are maximal, and energy expenditure is minimal. Rapid development should then be favored followed by a long lifespan and high adult survival. Positive associations among diverse fitness or life-history traits are expected, controlled by stress-resistant 'good genotypes'. Heterozygotes tend to show higher energetic efficiency and hence higher fitness than do corresponding homozygotes under extreme environments, and to give parallel associations among life-history traits. Energy budgets under abiotic environments are pivotal for integrative evolutionary studies of life histories in natural populations.

Animals↗
PubMedDate not supplied

Immunological biomarkers of ageing in man: changes in both innate and adaptive immunity are associated with health and longevity.

Scientific and clinical advances in the last century have led to increased numbers of individuals living to older ages. Thus a major concern is how to live these years with a high quality of life. The ageing immune system is less well able to cope with infectious diseases than the youthful immune system probably as a consequence of altered immune response to pathogens. Thus, both innate and adaptive immune responses show age-related changes that could be decisive for healthy ageing and survival. Longitudinal studies in healthy elderly have allowed the definition of the ''immune risk phenotype" (IRP) a predictor of mortality in elderly individuals that is based on several parameters of the adaptive immune response. Here, we hypothesize that failures in innate immunity observed in frail elderly are related to those alterations described in adaptive immunity defined as the IRP. It will be important to include assays of NK cell markers and functions in future longitudinal studies in order to investigate this point in detail as well as to consider the trace element zinc as an essential co-factor for optimal NK cell activity.

Aged, 80 and over↗
PubMed2006

Survival and longevity improvements at extreme ages: an interpretation assuming an ecological stress theory of aging.

The primary determinant of survival during aging is the energetic efficiency and metabolic stability required to counter the accumulated internal and external stresses of a lifetime. Hence, genetically stress-resistant individuals should accumulate with age; frailer, less robust, less energetically efficient and less metabolically stable individuals should succumb in parallel. This selection process implies the accumulation of energetically efficient stress-resistant individuals with age to the exclusion of all others. High additive genetic variability for survival is expected under extreme circumstances, however there is limited evidence close to the absolute extremes of life that diversity may fall. At this stage, only a few highly adaptive, oxidative-stress-resistant and presumably somewhat homozygous genotypes should remain. Therefore a fall in variability may occur in these outliers, when frailer individuals are unable to cope and are eliminated at extreme ages. This process could provide an explanation of mortality-rate declines in domesticated (laboratory) and free-living populations of the extremely old. That is, mortality-rate declines may be an expectation from a process of genetic sorting resulting from the accumulated responses to environmental stress over time. Application of an ecological stress theory of aging, which combines the external stresses to which organisms are exposed with internal stresses, appears to be the prerequisite for this conclusion.

Aging↗
PubMedDate not supplied

The genetics of exceptional human longevity.

How we age as individuals is no doubt a complex interaction of genetic and environmental factors. Studies of certain populations with optimal environments and health-related behaviors, as well as twin studies, suggest that the average set of genetic variations should facilitate the average person's ability to live to around age 85. Average life expectancies are lower than this because we generally fight survival advantage with bad health habits that can lead to premature aging, chronic illness, and death at a significantly younger age. Centenarians on the other hand live 15-25 years beyond what the average collection of us are able to achieve. Many of them have a history of aging relatively slowly, and either markedly delaying or even escaping lethal diseases associated with aging (Alzheimer's disease, stroke, cancer, cardiovascular disease, and diabetes). In order to live to such old age, centenarians are less likely to have genetic and environmental exposures that would cause at least lethal diseases at younger ages. Demographic selection is the drop out within a cohort, of genotypes linked to age-related lethal diseases and premature mortality as the cohort achieves older and older age. The result is a very old cohort that lacks these genotypes relative to younger age groups. Recent pedigree and molecular genetic studies indicate that scientists can use this selection to their advantage in discerning genotypes that play important roles in delaying or escaping diseases such as Alzheimer's disease, and in slowing the aging process.

Adult↗