Don't use email as a login
you can't update your email without deleting your entire person record. Bad practice to use email as a login. They change.
Stu Knapp commented
The HELP page for YOUR HEALTHVAULT ACCOUNT has an entry for "How do I change my sign-in information?" Step 3 says "At the bottom of the page under Sign-in information, click Add or edit sign-in information." I don't find anything about Sign-in information on that page. ????