As we get older, our hair goes through a number of changes.
Dr Erika Schwartz said via The New York Times: "Like everything else in aging, your hair suffers the consequences."
One change is the loss of melanin, the molecule responsible for hair colour.
"Thick, shiny hair is a hallmark of youth," said Dr Erika.
How quickly a person's hair loses colour has to do with genetics and the extent to which the hairline recedes.
Most people's hair also goes through telogen, the phase in which hair growth slows significantly.
Dr Dendy Engelman, a dermatologist, said via The New York Times: "I tell my patients they aren't imagining it. Hair really does spend less time in the growth phase as we get older."
In addition, hair follicles undergo changes that can result in thinner hair, also known as 'miniaturisation.'
"Think of your scalp like parched earth- when it is dehydrated, hair become less rooted," said Jeni Thomas (Procter and Gamble) via The New York Times.
Both men and women also experience a decrease in sebum production, which makes hair shiny.
Experts say that if you choose to combat these changes to your hair, make sure to update and maintain your new routines.
Debra Lin said via The New York Times: "A lot of women have figured out what worked for them in their 30s. But then they're hit with changes in their 40s and need to figure it out again."
"You can't just do something and stop. You have to keep it up if you want to maintain your results," said Plastic surgeon Dr Gary Linkov via the New York Times.
Sign up to W24's Newsletters so you don't miss out on any of our stories and giveaways