The science of ageing

The global population is ageing rapidly. A longer life is a blessing if the added years are spent in health. Cells, tissues, and organs all change with age and eventually, their function begins to deteriorate. The processes that determine ageing are very complex. There are two major groups of theories: programmed self-destruction, and stochastic. Ageing as a predetermined, genetically controlled process is supported by the characteristic lifespans of different species. There are several broad genetic theories: mutation accumulation theory, disposable soma theory, and theory of antagonistic pleiotropy. There are single genetic disorders that cause premature ageing. Hallmarks of ageing includes: genomic instability, telomere(definition) attrition, epigenetics, loss of proteostasis(definition), deregulated nutrient sensing, mitochondrial dysfunction(definition), cell senescence(definition), stem-cell exhaustion, altered intercellular communication, disabled macroautophagy, dysbiosis, and chronic inflammation. Ageing tissues are composed of ageing tissue-specific cells and ageing connective tissue.