You can look at the change documents for user to see changes to user attributes (user creation, deletion, locks, password changes, validity period, etc.) and changes to Roles/Profiles. In SU01 or from SUIM, you run the change documents for user report. In SU01, from Information menu-->Change Documents for Users. Not sure if this is what you're referring to...but this report does not include changes to user parameters. Hope this helps.