Actually, the opposite is true: astronauts age slower in space relative to people on the Earth’s surface due to the effects of time dilation.
According to Einstein’s theory of relativity, time can be experienced differently by observers who are moving relative to one another or who are in different gravitational fields. In the case of astronauts in space, they are moving at high speeds relative to the Earth and are also in a weaker gravitational field.
As a result, time passes more slowly for astronauts in space than it does for people on the Earth’s surface. This effect is known as time dilation, and it has been confirmed by experiments with high-precision atomic clocks on the International Space Station.
In practical terms, this means that over the course of a long space mission, such as a trip to Mars and back, astronauts would experience slightly less time than people on Earth, and therefore would age slightly less. This effect is very small, however, and would only become noticeable over very long periods of time.
So, in summary, astronauts age slower in space than they would on the Earth’s surface due to the effects of time dilation.