Age at start of hormone replacement medication use is based on self-report. Female participants are first asked if they have ever taken medication for hormone replacement. Those who respond "yes" are asked to identify the form of medication (e.g., pill, patch). Participants are then asked to report age at first use:

1. Did you ever take any type of estrogen hormonal medication, for example Premarin, Ogen, or Estrace, or progesterone hormonal medication, for example Provera?
2. Were these estrogen or progesterone hormones in the form of a pill, injection, vaginal cream or suppository, or skin patch?
3. How old were you when you first took this/these medications?

Note: If the response for either age at start of hormone replacement or age of last use is not valid, both values are set as missing.