Don’t drive yourself crazy. It really does not matter that much. Do whatever suits you. It is simply up to you to decide. Talk to your doctor about your needs and values, and come to an informed consent together. In the very worst case you pay for the screening out of your own pocket, that’s all (more likely your doctor states a justification and the screening is reimbursed). See also answer to C).
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C) The screening program should rather rely on a person’s health or the remaining life expectancy. Since these measures are difficult to derive and highly subjective, age has been found to be a well accepted, politically correct proxy. Think about a person that migrates between regions of low and high life expectancy, where also age recommendations for screening programs are adjusted accordingly. All of a sudden the very same person is or is no longer eligible to participate in a screening program.