This recoded variable is based on the following variables:

• COLLNO: Time since last colonoscopy: units

• COLLTP: Time since last colonoscopy: time period

• COLLDMO: Calendar month of last colonoscopy

• COLLDYR: Year of last colonoscopy

• COLLESTY: Time since last colonoscopy: grouped year estimate

The 2010 and 2015 Cancer Layout files note that, "This is a time category recode for the time since the most recent colonoscopy. All available information was used and the recoded variable was pre-filled with the response to the time category question first, if available. These data are provided by the respondent and are not imputed."

There is a similar variable that also reports the time since the respondent's most recent colonoscopy, COLLGYRR1, using the same method as the 2000 survey.