The Field Representative's Manual noted that the period described as "smoking the most" respondent could range from a month to years. It noted that if the respondent did not understand the question, interviewers should ask, "Was there any period in your life when you smoked more than you smoke now?"

In the 1970 survey, a respondent representing the family (a proxy) could answer the question associated with CIGSHEAVIEST for all other family members over age 17. As self-report is typically more accurate than proxy report, researchers may want to indicate this caveat when analyzing the data or interpreting results.