I am 61 now but back when I turned 40, in the US the suggestion was a baseline at 40, so I had one. I was also acutely aware of the danger of breast cancer due to a younger mother with kids my kids' ages dying of it. So, so sad. That said, because I have always had normal mammograms and have zero family history of breast cancer, now I get one every few years. I think family history and age matters.
Came back to add: what is gained by the small amount of radiation far exceeds any risk.