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Extrinsically induced senescent cells active intrinsic aging
While extrinsic and intrinsic aging are often thought of as separate, itβs clear that they actually intersect. Research has shown that external aging factors actually increase the rate at which we experience intrinsic aging. Scientists believe that cellular senescence may be the factor that links the two together.Extrinsic aging factors induce early senescence in cells, causing the body to act older than it actually is. With increasing exposure to these factors, the body can no longer keep up with the rate of senescence occurringβleading to an accumulation of senescent cells. These senescent cells secrete a wide range of factors collectively called the senescence-associated secretory phenotype (SASP). This is where the link to intrinsic aging comes into play. SASP itself can actually activate intrinsic aging β inducing inflammation, altering tissue homeostasis and promoting cellular dysfunction. This means that increasing rates of extrinsic aging can actually contribute to increasing rates of intrinsic aging through cellular senescence. When both extrinsic and intrinsic aging increase, we experience earlier onset of age-related diseases. For example, the accumulation of senescent cells in the brain can impair cognitive function and contribute to neurodegenerative diseases such as Alzheimer's.