Covid-19 stress may be manifesting in a telltale sign of aging.
Among the anticipated and dreaded effects of being shut in for weeks and weeks was the inevitable appearance of gray roots as growing hair revealed its current natural color. As one of my neighbors said, she wished she could have a mask for her head. She took to wearing hats even when it was cloudy, and attempted to cover her gray with ‘do-it-yourself’ kits from her local pharmacy. For others who thought the decision to color their hair was a decision they believed was several years in their future, gray strands suddenly appeared like the profusion of dandelions after a rainstorm. Was the gray there all along and discovered because of the new necessity of fussing with uncut, unkempt hair? Or were the new gray strands perhaps a consequence of the unrelenting stress of the pandemic?
Canities subita — the sudden, seemingly “overnight” onset of white hair — is a well-described dermatological condition that is sometimes referred to as “Marie Antoinette Syndrome.” There must be something about anticipating one’s execution the next morning that causes hair to lose all of its color. The Queen’s hair went from auburn to white the night before she was guillotined on Oct. 16, 1793. Mary Queen of Scots and Sir Thomas More also lost their hair color the night before they lost their heads. However, premature graying is not uncommon among those living a chronically stressful life. Pictures of the graying of President Obama’s hair during his eight-year tenure as head of state is also often used as an example.
Thus is it possible that the stress of the past few months and its continuation due to Covid-19 might hasten a natural process? Gray and/or white hair normally occurs with aging, and genetics plays a role in determining the age at which the first strands of gray appear. But as an article in Scientific American points out, when the graying of hair seems accelerated, scientists have suggested chronic stress as the cause.
As described in the article, the growth of hair takes place in a sort of assembly line. Hair production begins in epidermal cells found in the approximately 100,000 follicles on the scalp. These cells contain a colorless protein called keratin. The hair cells get their color from other cells called melanocytes in the follicles. These cells contain melanin, which is a pigment. Melanin comes in two shades: dark brown or black (eumelanin) and yellow or red (pheomelanin). For most of our life, new melanocytes continue to be made from melanocyte stem cells that live within each hair follicle. Eventually these stem cells disappear, and, with their disappearance, no new melanocytes containing melanin are formed. When that happens, hair growing out from the hair follicle has less and less pigment, and eventually will appear as gray or eventually white strands.
But this process, i.e. loss of melanocytes, may take decades to occur unless, as scientists have now discovered, the individual has been experiencing substantial stress.
This past winter, prior to the pandemic, researchers at Harvard University led by Dr. Ya-Chieh Hsu, reported that they may have found the link between stress and the production of the melanocytes. Using mice as a research model, researchers exposed them to three kinds of stress: mild short-term pain, psychological stress, and restricted movement. All three stresses caused both the loss of melanocytes and the pigment melanin. The obvious suspects—an immune reaction or too much cortisone—had no effect on the melanocyte production. However, they found that noradrenaline, the “fight or flight” neurotransmitter that is elevated under acute stress, was responsible indirectly for the graying of the animals’ fur. When they injected noradrenaline into non-stressed mice, new fur growth was gray: The melanocytes had disappeared.
It turned out to be a little more complicated. Noradrenaline (or norepinephrine) is released by the sympathetic nervous system. These nerves actually extend into each hair follicle and release noradrenaline into the follicle when the animal (or human) is stressed. The scientists saw that as this occurred, the stem cells that produce the melanocytes disappeared. The change was a permanent loss of melanocytes, and consequently a permanent loss of melanin. All new hair growth would be gray or white.
The irreversible effect of the stress was unanticipated by the scientists. Most of us who have not escaped the almost inevitable stresses of adult life know that it has a detrimental effect on our bodies, as well as on our emotional and cognitive states. Indeed, many rituals surrounding the mourner are based on the inability of someone who has experienced the death of a close family member to be able to function until some time has passed. And the effect of stress on a family caretaker, especially when the care extends for months or years, has been well defined. Moreover, many of us believe that when the stress relents or disappears, good nutrition, exercise, sleep, and perhaps relaxation and meditation will restore our bodies and minds to their former, unstressed state.
But if stress can shut off the production of certain cells in our hair follicles, what other permanent effects might it have?
“Hyperactivation of sympathetic nerves drives depletion of melanocyte stem cells,” Zhang, B, Ma S, Rahmin I et al, Nature 2020; 577:676–681.