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Graying hair is an inescapable part of growing older for most, as those first strands of silver appear to sprout for many people in their mid-30s — and by age 50, it's not unusual for half their hair to be gray.
Known by scientists as canities or achromotrichia, the graying of hair is a long-studied phenomenon that has a variety of causes. First, the good news: It's not going to kill you. In a 1998 study published in The Journals of Gerontology, researchers found no correlation between the mortality and the extent of graying of the hair among a random sample of 20,000 participants in a long-term cardiovascular study launched in 1975 in Copenhagen, Denmark.
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But why do we go gray?
Hairs appear to the naked eye as white, silver or gray absent the pigments that otherwise provide color in shades of black, brown, blond or red.
Within each hair follicle are cells, known as melanocytes, that produce one of two basic pigments: eumelanin or pheomelanin, depending on your DNA. Eumelanin is commonly present in black and brown hair, while pheomelanin is found in red, auburn and blond hair.
Unlike the melanin that colors skin, the pigments produced in scalp hairs typically degrade more slowly. That helps the hair keep its color as it grows out over an average of 3.5 years, according to a 2020 article in the journal Skin Appendage Disorders.
Gray hair develops as melanocytes decrease in number, but exactly when those cells begin to wane differs for each individual. However, there are some general trends. According to the article, “graying typically begins in the mid-30s for Caucasians, the late-30s for Asians, and the mid-40s for Africans."
The odd life of melanocytes
Scientists have recently shed new light on what may be happening to melanocyte stem cells as humans age. The new theory – backed by research reported in the journal Nature.
While hair itself may seem like a dead zone, hair follicles are a lively place. It’s here where melanocytes can be found moving around – particularly when we are young. On their journey, the stem cells receive signals (via proteins) that transform them into pigment factories that color our hair. That process, however, is interrupted as hair ages, sheds and then repeatedly grows back. When that happens, increasing numbers of melanocytes get stuck in places where they don’t receive the necessary signal to get busy, according to the research conducted on laboratory mice.
“The newfound mechanisms raise the possibility that the same fixed positioning of melanocyte stem cells may exist in humans,” study lead investigator Qi Sun, a postdoctoral fellow at New York University Langone Health, said in a statement. “If so, it presents a potential pathway for reversing or preventing the graying of human hair by helping jammed cells to move again between developing hair follicle compartments.”
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