We recommend asking demographics and sensitive questions at the end of a survey. This allows people time to adjust to answering the survey questions prior to being asked more invasive questions. It might also reduce the probability that someone opts to stop a survey early (e.g., if they are presented with demographic-related and/or invasive questions too early in the process). Of course, any questions that you include should always maintain the confidentiality of the participants, and none of the information you collect should make any respondent personally identifiable.