Population Dynamics

Dramatically extending the human lifespan seems increasingly possible. Many bioethicists object that life-extension will have Malthusian consequences as new Methuselahs accumulate, generation by generation. I argue for a Life-Years Response to the Malthusian Objection. If even a minority of each generation chooses life-extension, denying it to them deprives them of many years of extra life, and their total extra life-years are likely to exceed the total life-years of a majority who do not want life-extension.

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.

Comparative biogerontology evaluates cellular, molecular, physiological, and genomic properties that distinguish short-lived from long-lived species. These studies typically use maximum reported lifespan (MRLS) as the index with which to compare traits, but there is a general awareness that MRLS is not ideal owing to statistical shortcomings that include bias resulting from small sample sizes. Nevertheless, MRLS has enough species-specific information to show strong associations with many other species-specific traits, such as body mass, stress resistance, and codon usage.

Experimental data obtained from studies on the objects with different organization were analyzed. These data expand the ideas about the phenomenon of "viability determinate decrease in offspring of irradiated cells" discovered in the 1970s. This phenomenon was evaluated according to the standpoint of modern radiobiology.

This study examined maximum life span predictions obtained with the Gompertz mortality rate model, which assumes that there is a constant rate of acceleration in the age-related mortality of adult populations. The influence of population size N on the maximum life span (tmax) was shown to be small, because the numeric impact of N is reduced to ln[ln(N)]. In contrast, the Gompertz exponential mortality coefficient alpha has much more influence on the tmax, which varies as 1/alpha.

The health of the Portuguese has improved considerably in the last twenty years. Economic and social transformations that have contributed to the progressive amelioration of problems of feeding, sanitation, hygiene, housing and social conditions in general, as well as health services, have had decisive effect on this phenomenon. The spectacular regression of the indicators related to transmitted diseases, infant, perinatal (more than 50% between 1985 and 1994) and maternal mortality, and the mortality of children 1 to 4 yr old, also reflects this impact.

Secular growth has been occurring in Europe for about 150 years. In the USA, since 1900, each new generation has increased by an average of 1in (2.54cm) in height and about 10lb (4.54kg) in weight. This trend has generally been viewed as favorable and tallness is admired, with the current ideal height for a man in the Western world being 6ft 2in (188cm). The Japanese have increased in height since the end of the Second World War by about 5in (12.7cm) in height and the Chinese have been growing at the rate of 2.54cm/decade since the 1950s.

Aging research has benefited immensely from the application of genetics during the past decade. This success frequently obscures some of the latent difficulties associated with this method. Interpretations of many experiments are overly optimistic. The emerging functional methods spawned by the knowledge of the genome promise a new window on the biological aging process. However, conceptual approaches have not quite caught up with the technology.

As patients live longer, and more illnesses become chronic, comorbidity rates increase. This increase shows in attended morbidity registers, and its importance is revealed by the use of services, treatments, the survival rates and the patients life quality.

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.