Theories and Mechanisms of Aging

Ageing is a natural process with physiological changes in different body parts and has been associated with decreased reproductive capacity. Factors such as imbalance in the antioxidant defence system, vascular diseases, diabetes mellitus, accessory reproductive glands infection, obesity as well as buildup of toxic substances play a role in age-related male reproductive malfunction.

Age is inversely proportional to volume of semen, sperm count, sperm progressive motility, sperm viability, normal sperm morphology. The observed negative correlation between ageing and semen indices contributes to male infertility and reproductive decline. Normal levels of ROS, plays crucial role in facilitating sperm function, such as capacitation, hyper-activation, acrosome reaction as well as sperm–oocyte fusion; however, a substantial elevation in the endogenous level of ROS, especially in reproductive tissues, usually instigates destruction of sperm cells and heightened male infertility. Contrarily, antioxidants, such as vitamins C and E, beta-carotene, and micronutrients like zinc and folate, have been found by researchers to facilitate normal semen quality and male reproductive function.

Furthermore, the role of hormonal imbalance as a result of the compromised hypothalamic-pituitary-gonadal axis, Sertoli and Leydig cells disorder, and nitric oxide-medicated erectile dysfunction during ageing cannot be undermined.

The rise of life expectancy in current societies is not accompanied, to date, by a similar increase in healthspan, which represents a great socio-economic problem. It has been suggested that aging can be manipulated and then, the onset of all age-associated chronic disorders can be delayed because these pathologies share age as primary underlying risk factor. One of the most extended ideas is that aging is consequence of the accumulation of molecular damage. According to the oxidative damage theory, antioxidants should slow down aging, extending lifespan and healthspan. The present review analyzes studies evaluating the effect of dietary antioxidants on lifespan of different aging models and discusses the evidence on favor of their antioxidant activity as anti-aging mechanisms. Moreover, possible causes for differences between the reported results are evaluated.

Aging is psychosocially and biologically defined as being older. An aged or geriatric patient is defined as a person whose biological age is advanced. Aging can be characterized as a deterioration of the physiological functions essential for survival and fertility that is time-related. Aging is a complex spatial and temporal hierarchy of dynamic activities that are integrated over the life cycle of a complex dance. Thus aging is not easily dissected into disjoint subprocesses; it is a dynamic, multidimensional, hierarchical process. In most body structures, aging is followed by incremental modifications. Aging biology research focuses on understanding both the cellular and molecular mechanisms that underlie these changes and those that accompany the onset of age-related diseases. As time passes, aging takes place in a cell, an organ, or the whole body. It is a phase of every living thing that goes on through the whole adult life cycle. Aging is an organism’s sequential or incremental transition that results in an increased risk of fatigue, illness, and death. Aging is multifaceted. Therefore, there are various hypotheses each of which may clarify one or more aspects of aging. Aging in humans reflects the accumulation over time of changes in a human being that may involve social, psychological, and physical changes. Recent hypotheses are assigned to the concept of damage, whereby the accumulation of damage (including DNA oxidation) may cause biological systems to fail, or to the concept of programmed aging, whereby problems with internal processes (epigenomic maintenance can cause aging such as DNA methylation) are correlated with the causes of aging.

The number and proportion of elderly people continue to increase worldwide. The majority of the elderly have multiple medical conditions, often the result of changes in biological processes associated with aging. This leads to the use of multiple medications and increased risk for drug–drug interactions, drug–disease interactions, medication errors, and adverse drug reactions. This chapter highlights several important factors to consider when conducting safety evaluations for medicinal products used by elderly patients. These include age-related changes in pharmacokinetic and pharmacodynamic effects and the need for specialized data collection and analysis of elderly patient cohorts throughout the product life cycle. This chapter also addresses the importance of communicating risks and measures to minimize the risks to the growing elderly population.