Position statement on human aging

Geroscience: just another name or is there more to it?

The widespread use of the name 'geroscience' in the science of aging is sometimes met with a wary attitude by biogerontologists other than its inventors. Here, we provide an overview of its origin and evolution to assess what exactly it is and to discuss its theoretical and biological relationship to earlier movements of anti-aging medicine and biogerontology more generally. Geroscience posits that targeting aging may offer a cost-effective approach to improve late-life health in humans, and because aging is malleable in model organisms and what regulates this is sufficiently understood, the time is ripe for moving forward to translational and clinical research. The geroscience agenda has rebranded imagery of past traditions, yet the claim that therapies for human aging are ready or within the imminent future is contestable and on brand with tradition, even if biogerontology has made great progress in the past decades.

Insights into the Anti-Aging Prevention and Diagnostic Medicine and Healthcare

Aging is an irreversible and natural phenomenon that occurs as a person ages. Anti-aging medicine applies advanced science and medical technology to early detection, prevention, treatment, and reversal of age-related dysfunctions, disorders, and diseases. Therefore, anti-aging diagnostic medicine and healthcare are important factors in helping the elderly population lead healthy and active lives. However, it is challenging to diagnose various aging and related diseases accurately through various forms of anti-aging diagnostic medicine and health management. It may not be treated appropriately, so many older people are making various efforts to prevent aging themselves in advance. Therefore, anti-aging medicine and health care have been developed in various forms, from health checkups to alternative medicine and biophysical technology beyond simple clinical medicine, and are being applied to demand the needs of the elderly. This review intends to explore and characterize various applications related to anti-aging medicine and healthcare in the elderly. In addition, economic, medical, and ethical considerations arising from the relationship between the increase in the elderly population and the continuous development of anti-aging medicine can be considered.

Sarcopenia, a major clinical problem in old age, potential causes, clinical consequences and therapeutic possibilities

Sarcopenia or degeneration of skeletal muscle tissue with aging, is responsible for functional de-cline and loss of independence in older adults. The purpose of this article is to review the current definitions of sarcopenia, its potential causes, clinical consequences and the potential for prop-hylactic and curative intervention. Sarcopenia is recognized as a major clinical problem for the elderly, and the research in this area is growing exponentially. One of the most important recent developments has been convergence in the operational definition of sarcopenia that combines muscle mass, strength and muscle function. In 2010, the European Working Group on Sarcopenia in Oder People (EWGSOP) published a definition of sarcopenia aimed at promoting progress in the identification and care of the elderly. In early 2018 (EWGSOP2) he met again to update the original definition to reflect the scientific and clinical evidence that has been built over the past decade. The cause of sarcopenia is considered to be multifactorial: hormonal changes, neurologi-cal decline, sedentary / immobilization for a long period, chronic diseases, obesity, all these fac-tors contribute to the onset of sarcopenia. Prophylactic or curative interventions are essentially aimed at nutrition and exercise. Although pharmaceutical agents are developed that target seve-ral biological pathways, proper nutrition and specific physical exercises remain the gold stan-dard for therapy. Through this review, we want to draw attention to the need to implement complex analyzes of the elderly patient, regardless of the acute problem with which he presents himself at the consultation. These analyses should contain tests, measurements, questionnaires that identify in time a possible musculoskeletal degeneration. The results did not show any sig-nificant difference between the perception of sarcopenia, the way of approaching it and the prophylactic or therapeutic treatment. We focused on this pathology because sarcopenia is rela-tively newly observed, defined, it is not fully investigated and a clinical skill has not been for-med for the evaluation of the elderly patient. Keywords: Skeletal muscle, elderly, sarcopenia, degeneration, exercises

Age-Related Dysfunctions: Evidence and Relationship with Some Risk Factors and Protective Drugs

The theories interpreting senescence as a phenomenon favored by natural selection require the existence of specific, genetically determined and regulated mechanisms that cause a progressive age-related increase in mortality. The mechanisms defined in the subtelomere-telomere theory suggest that progressive slackening of cell turnover and decline in cellular functions are determined by the subtelomere-telomere-telomerase system, which causes a progressive "atrophic syndrome" in all organs and tissues. If the mechanisms underlying aging-related dysfunctions are similar and having the same origin, it could be hypothesized that equal interventions could produce similar effects. This article reviews the consequences of some factors (diabetes, obesity/dyslipidemia, hypertension, smoking, moderate use and abuse of alcohol) and classes of drugs [statins, angiotensin-converting enzyme (ACE) inhibitors, sartans] in accelerating and anticipating or in counteracting the process of aging. The evidence is compatible with the programmed aging paradigm and the mechanisms defined by the subtelomere-telomere theory but it has no obvious discriminating value against the theories of non-programmed aging paradigm. However, the existence of mechanisms, determined by the subtelomere-telomere-telomerase system and causing a progressive age-related decline in fitness through gradual cell senescence and cell senescence, is not justifiable without an evolutionary motivation. Their existence is expected by the programmed aging paradigm, while is incompatible with the opposite paradigm.

Elimination of Senescent Cells: Prospects According to the Subtelomere-Telomere Theory

Cell senescence is an artificially reversible condition activated by various factors and characterized by replicative senescence and typical general alteration of cell functions, including extra-cellular secretion. The number of senescent cells increases with age and contributes strongly to the manifestations of aging. For these reasons, research is under way to obtain "senolytic" compounds, defined as drugs that eliminate senescent cells and therefore reduce aging-associated decay, as already shown in some experiments on animal models. This objective is analyzed in the context of the programmed aging paradigm, as described by the mechanisms of the subtelomere-telomere theory. In this regard, positive effects of the elimination of senescent cells and limits of this method are discussed. For comparison, positive effects and limits of telomerase activation are also analyzed, as well of the combined action of the two methods and the possible association of opportune gene modifications. Ethical issues associated with the use of these methods are outlined.

Protective Effect of Human Leukocyte Antigen (HLA) Allele DRB1*13:02 on Age-Related Brain Gray Matter Volume Reduction in Healthy Women

BACKGROUND

Reduction of brain volume (brain atrophy) during healthy brain aging is well documented and dependent on genetic, lifestyle and environmental factors. Here we investigated the possible dependence of brain gray matter volume reduction in the absence of the Human Leukocyte Antigen (HLA) allele DRB1*13:02 which prevents brain atrophy in Gulf War Illness (James et al., 2017).

METHODS

Seventy-one cognitively healthy women (32-69years old) underwent a structural Magnetic Resonance Imaging (sMRI) scan to measure the volumes of total gray matter, cerebrocortical gray matter, and subcortical gray matter. Participants were assigned to two groups, depending on whether they lacked the DRB1*13:02 allele (No DRB1*13:02 group, N=60) or carried the DRB1*13:02 allele (N=11). We assessed the change of brain gray matter volume with age in each group by performing a linear regression where the brain volume (adjusted for total intracranial volume) was the dependent variable and age was the independent variable.

FINDINGS

In the No DRB1*13:02 group, the volumes of total gray matter, cerebrocortical gray matter, and subcortical gray matter were reduced highly significantly. In contrast, none of these volumes showed a statistically significant reduction with age in the DRB1*13:02 group.

INTERPRETATION

These findings document the protective effect of DRB1*13:02 on age-dependent reduction of brain gray matter in healthy individuals. Since the role of this allele is to connect to matching epitopes of external antigens for the subsequent production of antibodies and elimination of the offending antigen, we hypothesize that its protective effect may be due to the successful elimination of such antigens to which we are exposed during the lifespan, antigens that otherwise would persist causing gradual brain atrophy. In addition, we consider a possible beneficial role of DRB1*13:02 attributed to its binding to cathepsin S, a known harmful substance in brain aging (Wendt et al., 2008). Of course, other factors covarying with the presence of DRB1*13:02 could be involved.

Conserved and species-specific molecular denominators in mammalian skeletal muscle aging

Aging is a complex phenomenon involving functional decline in multiple physiological systems. We undertook a comparative analysis of skeletal muscle from four different species, i.e. mice, rats, rhesus monkeys, and humans, at three different representative stages during their lifespan (young, middle, and old) to identify pathways that modulate function and healthspan. Gene expression profiling and computational analysis revealed that pathway complexity increases from mice to humans, and as mammals age, there is predominantly an upregulation of pathways in all species. Two downregulated pathways, the electron transport chain and oxidative phosphorylation, were common among all four species in response to aging. Quantitative PCR, biochemical analysis, mitochondrial DNA measurements, and electron microscopy revealed a conserved age-dependent decrease in mitochondrial content, and a reduction in oxidative phosphorylation complexes in monkeys and humans. Western blot analysis of key proteins in mitochondrial biogenesis discovered that (i) an imbalance toward mitochondrial fusion occurs in aged skeletal muscle and (ii) mitophagy is not overtly affected, presumably leading to the observed accumulation of abnormally large, damaged mitochondria with age. Select transcript expression analysis uncovered that the skeletal inflammatory profile differentially increases with age, but is most pronounced in humans, while increased oxidative stress (as assessed by protein carbonyl adducts and 4-hydroxynonenal) is common among all species. Expression studies also found that there is unique dysregulation of the nutrient sensing pathways among the different species with age. The identification of conserved pathways indicates common molecular mechanisms intrinsic to health and lifespan, whereas the recognition of species-specific pathways emphasizes the importance of human studies for devising optimal therapeutic modalities to slow the aging process.

Aging is a complex phenomenon involving functional declines in multiple physiological systems with the passage of time. Focusing on skeletal muscle, a group of international scientists identified pathways involved in healthspan and by determining global gene expression profiles across species they exposed common mechanisms fundamental to the aging process. Their experimental design involved comparative analysis of mice, rats, rhesus monkeys and humans, targeting three key time points during their respective lifespans. Pathways related to oxidative stress, inflammation and nutrient signaling, which function collectively to affect the quality and status of mitochondria, emerged across all species in an age-influenced manner. The identification of conserved pathways reveals molecular mechanisms intrinsic to health and survival, whereas the unveiling of species-specific pathways emphasizes the importance of human studies for devising optimal therapeutic modalities to slow the aging process.

Targeting glucose metabolism for healthy aging

Advancing age is the greatest single risk factor for numerous chronic diseases. Thus, the ability to target the aging process can facilitate improved healthspan and potentially lifespan. Lack of adequate glucoregulatory control remains a recurrent theme accompanying aging and chronic disease, while numerous longevity interventions result in maintenance of glucoregulatory control. In this review, we propose targeting glucose metabolism to enhance regulatory control as a means to ameliorate the aging process. We highlight that calorie restriction improves glucoregulatory control and extends both lifespan and healthspan in model organisms, but we also indicate more practical interventions (i.e., calorie restriction mimetics) are desirable for clinical application in humans. Of the calorie restriction mimetics being investigated, we focus on the type 2 diabetes drug acarbose, an α-glucosidase inhibitor that when taken with a meal, results in reduced enzymatic degradation and absorption of glucose from complex carbohydrates. We discuss alternatives to acarbose that yield similar physiologic effects and describe dietary sources (e.g., sweet potatoes, legumes, and berries) of bioactive compounds with α-glucosidase inhibitory activity. We indicate future research should include exploration of how non-caloric compounds like α-glucosidase inhibitors modify macronutrient metabolism prior to disease onset, which may guide nutritional/lifestyle interventions to support health and reduce age-related disease risk.

Historical improvements in well-being do not hold in late life: Birth- and death-year cohorts in the United States and Germany

One key objective of life span research is to examine how individual development is shaped by the historical time people live in. Secular trends favoring later-born cohorts on fluid cognitive abilities have been widely documented, but findings are mixed for well-being. It remains an open question whether secular increases in well-being seen in earlier phases of life also manifest in the last years of life. To examine this possibility, we made use of longitudinal data obtained from the mid-1980s until the late 2000s in 2 large national samples in the United States (Health and Retirement Study [HRS]) and Germany (German Socio-Economic Panel [SOEP]). We operationally defined historical time from 2 complementary perspectives: birth-year cohorts based on the years in which people were born (earlier: 1930s vs. later: 1940s) and death-year cohorts based on the years in which people died (earlier: 1990s vs. later: 2000s). To control for relevant covariates, we used case-matched groups based on age (at death) and education and covaried for gender, health, and number of observations. Results from both countries revealed that well-being in old age was indeed developing at higher levels among later-born cohorts. However, for later-deceased cohorts, no evidence for secular increases in well-being was found. To the contrary, later-dying SOEP participants reported lower levels of well-being at age 75 and 2 years prior to death and experienced steeper late-life declines. Our results suggest that secular increases in well-being observed in old age do not manifest in late life, where "manufactured" survival may be exacerbating age- and mortality-related declines.

[Anti-aging medicine: notes on a socio-technical controversy]

After some decades of struggle, geriatrics and gerontology have become the legitimate sciences of aging. Today, their status is being questioned. In its short history, anti-aging medicine has taken root as a medical practice that questions how to address biological aging. In so doing, all medicine is questioned. Here, we explore in particular how this controversy is structured around the founding principles of the sciences of aging. Is there any basis for these questionings? How have they been treated by those who have received them? Taking a socio-technical viewpoint, it is worth considering that for geriatricians and gerontologists, the need to criticize anti-aging medicine also raises some important reflections about how the sciences of aging address their subject.

Cellular aging in depression: Permanent imprint or reversible process?: An overview of the current evidence, mechanistic pathways, and targets for interventions

Depression might be associated with accelerated cellular aging. However, does this result in an irreversible state or is the body able to slow down or recover from such a process? Telomeres are DNA-protein complexes that protect the ends of chromosomes and generally shorten with age; and therefore index cellular aging. The majority of studies indicate that persons with depression have shorter leukocyte telomeres than similarly aged non-depressed persons, which may contribute to the observed unfavorable somatic health outcomes in the depressed population. Some small-scale preliminary studies raise the possibility that behavioral or pharmacological interventions may either slow down or else reverse this accelerated telomere shortening, possibly through increasing the activity of the telomere-lengthening enzyme telomerase. This paper covers the current state of evidence in the relationship between depression and the telomere-telomerase system and debates whether depression-related cellular aging should be considered a reversible process or permanent damage.

Effect of ecological walking training in sedentary elderly people: act on aging study

PURPOSE OF THE STUDY

This study aims to investigate the effects of a walking program on aerobic endurance and function in a sample of sedentary elderly people.

DESIGN AND METHODS

For this study, 126 sedentary individuals were recruited: 63 individuals (mean age = 74.1±6.0 years) for the control group and 63 (mean age = 72.0±4.5 years) for the intervention group. The intervention consisted of walking training including balance exercises and lower limb strength activities twice a week for 4 months. We collected baseline and post-test measurements of aerobic endurance, lower limb strength, and mobility. We also measured aerobic endurance at increments of 4, 8, and 12 weeks between the baseline and the post-test. We used analyses of covariance with baseline value, gender, age, and body mass index scores as covariates (p < . 05) and calculated the effect size for the effects of the intervention. The changeover time of aerobic endurance was also analyzed with the repeated analysis of variance (p < .05).

RESULTS

The intervention group showed steady and significant improvements with respect to the 6-min walk (aerobic endurance) from 447.89 m (SD 73.87) to 561.51 m (SD 83.96), as well as the 30-s chair stand (lower limb strength) from 10 (SD 3) to 13 (SD 3) number of times and the Timed Up and Go Test (mobility) from 8.53 s (SD 2.86) to 7.13 s (SD 1.76) at the post-test, whereas the control group showed significant decrease in all measurements.

IMPLICATION

These results underline that an ecological walking training program can be used to improve physical functioning among sedentary elderly people.

The Right and Wrong of Growing Old: Assessing the Argument from Evolution

One argument which is frequently levelled against the enhancement of human biology is that we do not understand the evolved function of our bodies well enough to meddle in our biology without producing unintended and potentially catastrophic effects. In particular, this argument is levelled against attempts to slow or eliminate the processes of human ageing, or 'senescence', which cause us to grow decrepit before we die. In this article, I claim that even if this argument could usefully be applied against attempts to enhance other human traits, it cannot be valid in the case of attempts to enhance the various processes that constitute senescence. I begin by reviewing the biology of ageing to show how it consists of a number of unrelated traits. Then, following the arguments of a number of evolutionary biologists, I explain that every one of these traits is a product of evolutionary 'neglect' rather than 'intent'. Finally, I consider the strongest version of the argument against enhancing senescence, which acknowledges these facts about the evolution of ageing but insists that we have nevertheless have prudential reasons to avoid enhancement wherever there is some uncertainty about the genetics or evolutionary function of a trait. I provide two reasons for rejecting this version of the argument as well, even in the case of human senescence, where such uncertainty is currently significant.

An aging program at the systems level?

Many genes and pathways are known to modulate lifespan in various organisms, but it remains unclear whether there exists a common aging program, and how individual variations of lifespan can occur in an isogenic population. Recent studies on aging regulation at the systems and epigenetic levels point to the possibility of regulating and potentially reversing the aging epigenome and transcriptome, resulting in differential aging status and aging rate in different individuals. Here, the author summarize some of these findings and discuss the possibility of integrating multiple layers of aging regulation at the systems level, to identify an aging program that can explain lifespan variations introduced by environmental and developmental history.

Cohorts based on decade of death: no evidence for secular trends favoring later cohorts in cognitive aging and terminal decline in the AHEAD study

Studies of birth-year cohorts examined over the same age range often report secular trends favoring later-born cohorts, who are cognitively fitter and show less steep cognitive declines than earlier-born cohorts. However, there is initial evidence that those advantages of later-born cohorts do not carry into the last years of life, suggesting that pervasive mortality-related processes minimize differences that were apparent earlier in life. Elaborating this work from an alternative perspective on cohort differences, we compared rates of cognitive aging and terminal decline in episodic memory between cohorts based on the year participants had died, earlier (between 1993 and 1999) or later in historical time (between 2000 and 2010). Specifically, we compared trajectories of cognitive decline in 2 death-year cohorts of participants in the Asset and Health Dynamics Among the Oldest Old study that were matched on age at death and education and controlled for a variety of additional covariates. Results revealed little evidence of secular trends favoring later cohorts. To the contrary, the cohort that died in the 2000s showed a less favorable trajectory of age-related memory decline than the cohort that died in the 1990s. In examinations of change in relation to time to death, the cohort dying in the 2000s experienced even steeper terminal declines than the cohort dying in the 1990s. We suggest that secular increases in "manufacturing" survival may exacerbate age- and mortality-related cognitive declines among the oldest old.

Impaired iron status in aging research

Aging is associated with disturbances in iron metabolism and storage. During the last decade, remarkable progress has been made toward understanding their cellular and molecular mechanisms in aging and age-associated diseases using both cultured cells and animal models. The field has moved beyond descriptive studies to potential intervention studies focusing on iron chelation and removal. However, some findings remain controversial and inconsistent. This review summarizes important features of iron dyshomeostasis in aging research with a particular emphasis on current knowledge of the mechanisms underlying age-associated disorders in rodent models.

Cohort differences in cognitive aging and terminal decline in the Seattle Longitudinal Study

Life span researchers have long been interested in how and why fundamental aspects of human ontogeny differ between cohorts of people who have lived through different historical epochs. When examined at the same age, later born cohorts are often cognitively and physically fitter than earlier born cohorts. Less is known, however, about cohort differences in the rate of cognitive aging and if, at the very end of life, pervasive mortality-related processes overshadow and minimize cohort differences. We used data on 5 primary mental abilities from the Seattle Longitudinal Study (Schaie, 2005) to compare both age-related and mortality-related changes between earlier born cohorts (1886-1913) and later born cohorts (1914-1948). Our models covary for several individual and cohort differences in central indicators of life expectancy, education, health, and gender. Age-related growth models corroborate and extend earlier findings by documenting level differences at age 70 of up to 0.50 SD and less steep rates of cognitive aging on all abilities between 50 and 80 years of age favoring the later born cohort. In contrast, mortality-related models provide limited support for positive cohort differences. The later born cohort showed steeper mortality-related declines. We discuss possible reasons why often reported positive secular trends in age-related processes may not generalize to the vulnerable segment of the population that is close to death and suggest routes for further inquiry.

Longevity in the 21st Century

The main objective of this paper is to offer a detailed analysis of mortality change in the United Kingdom at the beginning the 21st century. Starting from an exploration of 20th century mortality trends, focusing in particular on the 1990s, underlying forces driving trends in longevity are discussed. These include the ‘cohort effect’ and the ‘ageing of mortality improvement’. International mortality statistics and trends are also analysed. The pace of medical advances is discussed, with specific focus on research into the ageing process and a potential treatment for cardiovascular disease. The paper also discusses the potential threat from infectious diseases.

The analysis of underlying trends suggests that life expectancy in retirement in the U.K. is likely to increase rapidly in the early part of the 21st century. Some scientists are also claiming that we will be seeing the fruits of anti-ageing research within just a few decades.

A core theme of the paper is that future projections should be grounded in as good an understanding of the past as possible. Different methods for projecting future rates of mortality are discussed, and it is noted that emphasis should be placed on the uncertainty surrounding projections.

The financial impact of using different assumptions for future mortality is explored. Significant differences in the cost of an annuity or pension arise from the use of the various projection bases.

Life assurance companies have already declared significant losses as a result of strengthening reserves on annuity portfolios. Taken together, future increases in life expectancy, increasing awareness of the risk of providing longevity insurance, changes in legislation and shortages in market capacity and capital, may well lead to worsening annuity rates.

It is difficult to assess the precise impact of future changes in life expectancy on final salary pension schemes. There is a lack of readily available information on the mortality assumptions being used in practice. It is therefore suggested that more disclosure in this area would be helpful. Employers sponsoring final salary schemes are making promises to their employees that extend up to 70 or 80 years into the future. Actuaries should be clear in spelling out to employers and trustees the nature of the risks behind the promises they are making. Future scheme design should reflect the possibility of substantial increases in life expectancy.

An over-riding implication of the anticipated increases in life expectancy is that people will remain in work for longer in the future. The age at which people retire will inevitably have to increase, and this trend will necessarily drive changes in all aspects of our society. As actuaries we have a vital role in helping to inform the wider debate.

What is lifespan regulation and why does it exist?

The development of a unified conceptual framework for the field of biogerontology has been impeded by confusing and misleading terminology. Thus, distinctions and definitions are provided for key terms (and their concepts) used in the paper: senescence, lifespan, potential lifespan, essential lifespan, and lifespan regulation. An organismal perspective is then used to examine the relationships between reproduction, lifespan regulation and senescence. The principal conclusions drawn from this examination are: (1) the inevitability of death makes physiological investments in reproduction a higher priority than somatic maintenance, (2) the race between reproduction and death creates a probabilistic window of time (essential lifespan) within which reproduction must occur, (3) the integrated network of genetic processes responsible for achieving essential lifespan (lifespan regulation) must be evolutionarily conserved and extensively regulated, (4) senescence is a stochastic byproduct of these regulated processes rather than a direct target of natural selection, and (5) genomic instability (an important stochastic component of senescence) plays no active role in lifespan regulation.

Tragedy and delight: the ethics of decelerated ageing

Biogerontology is sometimes viewed as similar to other forms of biomedical research in that it seeks to understand and treat a pathological process. Yet the prospect of treating ageing is extraordinary in terms of the profound changes to the human condition that would result. Recent advances in biogerontology allow a clearer view of the ethical issues and dilemmas that confront humanity with respect to treating ageing. For example, they imply that organismal senescence is a disease process with a broad spectrum of pathological consequences in late life (causing or exascerbating cardiovascular disease, cancer, neurodegenerative disease and many others). Moreover, in laboratory animals, it is possible to decelerate ageing, extend healthy adulthood and reduce the age-incidence of a broad spectrum of ageing-related diseases. This is accompanied by an overall extension of lifespan, sometimes of a large magnitude. Discussions of the ethics of treating ageing sometimes involve hand-wringing about detrimental consequences (e.g. to society) of marked life extension which, arguably, would be a form of enhancement technology. Yet given the great improvements in health that decelerated ageing could provide, it would seem that the only possible ethical course is to pursue it energetically. Thus, decelerated ageing has an element of tragic inevitability: its benefits to health compel us to pursue it, despite the transformation of human society, and even human nature, that this could entail.

[Is there any scientific evidence supporting antiaging medicine?]

The objective of antiaging medicine is to interfere in the normal human biological aging process. Is there any scientific basis to justify classifying antiaging medicine as a medical specialty and not a branch of basic biological science? This review evaluated 110 papers, nine of which (8.2% of the total) reported studies involving human subjects. Only one of these studies was randomized and double-blinded (Jadad 2). In accordance with their classification of recommendations and level of evidence, these studies were considered CII. Three of the nine articles were published in journals with an impact factor over 1.110. Therefore, there does not appear to be any solid scientific and/or clinical evidence that would justify the application of antiaging medicine in current medical practice.

Dietary interventions to extend life span and health span based on calorie restriction

The societal impact of obesity, diabetes, and other metabolic disorders continues to rise despite increasing evidence of their negative long-term consequences on health span, longevity, and aging. Unfortunately, dietary management and exercise frequently fail as remedies, underscoring the need for the development of alternative interventions to successfully treat metabolic disorders and enhance life span and health span. Using calorie restriction (CR)-which is well known to improve both health and longevity in controlled studies-as their benchmark, gerontologists are coming closer to identifying dietary and pharmacological therapies that may be applicable to aging humans. This review covers some of the more promising interventions targeted to affect pathways implicated in the aging process as well as variations on classical CR that may be better suited to human adaptation.

Mosaic aging

Although all multicellular organisms undergo structural and functional deterioration with age, senescence is not a uniform process. Rather, each organism experiences a constellation of changes that reflect the heterogeneous effects of age on molecules, cells, organs and systems, an idiosyncratic pattern that we refer to as mosaic aging. Varying genetic, epigenetic and environmental factors (local and extrinsic) contribute to the aging phenotype in a given individual, and these agents influence the type and rate of functional decline, as well as the likelihood of developing age-associated afflictions such as cardiovascular disease, arthritis, cancer, and neurodegenerative disorders. Identifying key factors that drive aging, clarifying their activities in different systems, and in particular understanding how they interact will enhance our comprehension of the aging process, and could yield insights into the permissive role that senescence plays in the emergence of acute and chronic diseases of the elderly.

Epidemiology of aging

Over the past century, truly remarkable changes have been observed in the health of older persons throughout the world, and these changes have strongly impacted society. The growth of the older population has resulted mostly from a general increase in the overall population size but is also strongly influenced by major declines in leading causes of mortality. These demographic transformations reverberate in society, increasing medical care and social needs, which are expected to increase steeply in the years to come. Based on demographic and epidemiologic perspectives, these changes were already detectable decades before and should have prompted radical changes in the structure and function of our system of health and social protection at that time. We come to this enormous challenge unprepared.

Does senescence give rise to disease?

The distinctions between senescence and disease are blurred in the literature of evolutionary biology, biodemography, biogerontology and medicine. Theories of senescence that have emerged over the past several decades are based on the concepts that organisms are a byproduct of imperfect structural designs built with imperfect materials and maintained by imperfect processes. Senescence is a complex mixture of processes rather than a monolithic process. Senescence and disease have overlapping biological consequences. Senescence gives rise to disease, but disease does not give rise to senescence. Current data indicate that treatment of disease can delay the age of death but there are no convincing data that these interventions alter senescence. An understanding of these basic tenets suggests that there are biological limits to duration of life and the life expectancy of populations and reveal biological domains where the development of interventions and/or treatments may modulate senescence.

Anti-aging science: The emergence, maintenance, and enhancement of a discipline

Through archival analysis this article traces the emergence, maintenance, and enhancement of biogerontology as a scientific discipline in the United States. At first, biogerontologists' attempts to control human aging were regarded as a questionable pursuit due to: perceptions that their efforts were associated with the long history of charlatanic, anti-aging medical practices; the idea that anti-aging is a "forbidden science" ethically and scientifically; and the perception that the field was scientifically bereft of rigor and scientific innovation. The hard-fought establishment of the National Institute on Aging, scientific advancements in genetics and biotechnology, and consistent "boundary work" by scientists, have allowed biogerontology to flourish and gain substantial legitimacy with other scientists and funding agencies, and in the public imagination. In particular, research on genetics and aging has enhanced the stature and promise of the discipline by setting it on a research trajectory in which explanations of the aging process, rather than mere descriptions, have become a central focus. Moreover, if biogerontologists' efforts to control the processes of human aging are successful, this trajectory has profound implications for how we conceive of aging, and for the future of many of our social institutions.

'Healthy Ageing' policies and anti-ageing ideologies and practices: on the exercise of responsibility

This paper explores how the exercise of the ethics of 'responsibility' for health care advanced through 'healthy ageing' and 'successful ageing' narratives in Western countries animates an array of 'authorities', including the 'anti-ageing medicine' movement as a strategy to address the anxieties of growing old in Western societies and as a tool to exercise the ethos of 'responsibility'. The choice of this type of authority as a source of guidance for self-constitution and the exercise of the 'responsible self', this paper will argue, enables the enactment of a type of late modernity notion of citizenship for ageing individuals based on principles of agelessness, health, independence and consumption power. Through interviews with anti-ageing consumers, however, it is also possible to argue the existence of tensions and contradictions that such a rigid model of self-constitution in later life produces, and the potential forms of resistance and contestations that may emerge as a result. In this way the current 'war on anti-ageing medicine' (Vincent 2003) becomes also symptomatic of bigger 'wars' taking place not only between institutions competing for control over knowledge and management of ageing, but between those in favour and against the homogenisation of life under the language of universal science, reason and market rationality.

The metal ion theory of ageing: dietary target hazard quotients beyond radicals

Numerous theories of ageing exist and many are interconnected when viewed through a modern integrative biology perspective. Diet provides a link to a large number of the theories that prevail at the molecular levels. In particular, metal ions form key elements of the radical theory along with having established roles in several age-related neurodegenerative disorders. Lifetime exposure to metals has been linked to ageing by contributions to oxidative stress and neurodegenerative disorders. As many foodstuffs contain high levels and diverse profiles of metals, their cumulative effect on ageing warrants investigation. The cumulative level of concern from environmental exposure can be expressed as a dimensionless index of target hazard quotient (THQ) or for known carcinogens, the target cancer risk (TR). This paper posits that a quantifiable relationship exists between ageing and level of concern resulting from cumulated metal exposure; and that this relationship can be used to develop an ageing-related index of concern from chronic metal ion exposure. As individual differences may facilitate or moderate this cumulated exposure, the potential influence on ageing or on the development of neurodegenerative disorders should be included into the model.

Human subjects protections in biomedical enhancement research: assessing risk and benefit and obtaining informed consent

The protection of human subjects in biomedical research relies on two principal mechanisms: assessing and comparing the risks and potential benefits of proposed research, and obtaining potential subjects' informed consent. While these have been discussed extensively in the literature, no attention has been paid to whether the processes should be different when the objective of an experimental biomedical intervention is to improve individual appearance, performance, or capability ("enhancement research") rather than to prevent, cure, or mitigate disease ("health-oriented research"). This essay examines this question in order to ensure that subjects in biomedical enhancement research receive adequate protection.

'Anti-Aging Medicine' and the Cultural Context of Aging in Australia: Preliminary Findings from Ongoing Research on Users and Providers of 'Anti-Aging Medicine' in Australia

This paper explores the management of the aging body within the anti-aging discourse and its implications on notions of "successful" and "healthy" aging policies. By looking at some of the preliminary findings of our current study of 'anti-aging medicine' in Australia, including interviews conducted with stakeholders in the anti-aging debate, this study explores some recurrent values and perceptions regarding 'anti-aging medicine,' the re-negotiation of boundaries between illness and health, and the social, cultural, and economic forces shaping understandings and practices around aging and decisions to use anti-aging technologies.

Protagonistic pleiotropy: Why cancer may be the only pathogenic effect of accumulating nuclear mutations and epimutations in aging

Since Szilard's seminal 1959 article, the role of accumulating nuclear DNA (nDNA) damage -- whether as mutations, i.e. changes to sequence, or as epimutations, i.e. adventitious but persistent alterations to methylation and other decorations of nDNA and histones -- has been widely touted as likely to contribute substantially to the aging process throughout the animal kingdom. Such damage certainly accumulates with age and is central to one of the most prevalent age-related causes of death in mammals, namely cancer. However, its role in contributing to the rates of other aspects of aging is less clear. Here I argue that, in animals prone to cancer, evolutionary pressure to postpone cancer will drive the fidelity of nDNA maintenance and repair to a level greatly exceeding that needed to prevent nDNA damage from reaching levels during a normal lifetime that are pathogenic other than via cancer or, possibly, apoptosis resistance. I term this the "protagonistic pleiotropy of chromosomal damage" (PPCD) hypothesis, because this interaction of cancer-related and -unrelated damage is the converse of the well-known "antagonistic pleiotropy" phenomenon. I then consider a selection of recent data on the rate of accumulation of nDNA damage in the context of this hypothesis, and conclude that all presently available evidence is consistent with it. If this conclusion is correct, the implications for the feasibility of greatly postponing mammalian (and eventually human) aging and age-related pathology are far-reaching.