The changing understanding of ageing. Part 1: Evaluating ageing theories and studies

This is the first of three discussions on emerging views of ageing, its derivation, and ageing-related diseases. To offer a context for the series, this first report briefly reviews several major early and recent theoretical debates. Arguments for and against several well-known ageing theories are presented for their veterinary relevance, including mutation, pleiotropy, reproduction-longevity trade-offs, oxygen metabolism and ageing as a genomically programmed product of natural selection. Additionally, the author presents commonly encountered problems when reading to interpret laboratory and population studies of ageing, offering busy clinicians a perspective on evaluating complex papers that analyse ageing-related data. Included among these problems are categorising intrinsic and extrinsic diseases, contrasts between laboratory-based and population-based observations, over-generalising research outcomes, short-term and long-term studies, and theoretical treatises. Central ideas of these discussions include why post-reproductive life span is relatively common among animals, the nature of age-related diseases relative to stochastic or programmed origins and the disease-related implications.