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Number of biological sons under 50 when first diagnosed with colon cancer


BSACLCAN is a two-digit count variable.

21: Top code of 21 or more
96: Not in Universe
97: Unknown-Refused
98: Unknown-Not Ascertained
99: Unknown-Don't Know


For sample adults with at least one biological son (BSNUM) who ever had colon cancer (BSCLCAN), BSACLCAN reports the number of the respondent's biological sons who were under 50 years of age when the colon cancer was first diagnosed.

Beginning in 2015, details about colon cancer (and several other cancer types) were suppressed because of low frequencies of these types of cancer among family members. Cancers of the colon and rectum are not available separately on the NHIS public use files to protect confidentiality; the number of biological sons under 50 years of age when diagnosed with these cancer types are all combined in BSCLRCAN, which reports the number of biological who were under the age of 50 when diagnosed with colorectal cancer.

BSACLCAN is one of a series of related variables in the "Family History" section of the 2000, 2005, and 2010 Cancer Modules. In all three years, this section begins with the general comment:

We would like to ask you a few questions about your family history of cancer.

According to the 2000 and 2005 Field Representative's Manuals, the purpose of this and other family cancer history questions is to "determine the prevalence of cancer in families in the population" to "allow a greater understanding of how data obtained from genetics clinics can be applied to the general population." The 2010 Manual provides a similar rationale, stating that the collection of this data "will allow analysts a greater understanding of how family history relates to cancer."

The Manuals for all three years define "biological" relatives as people related by blood. Thus, a respondent's biological son is a son related to the respondent by blood (i.e., not a stepson, adopted son, foster son, or son-in-law).


BSACLCAN is fully comparable between 2005 and 2010.

BSACLCAN is largely comparable between 2000 and 2005/2010, though there may be some difference in the meaning of "refused," "not ascertained," and "don't know" as used in 2000 compared to the meanings of those terms in 2005 and 2010.

The Survey Descriptions for all three years caution that while "all sample adults were to be asked the questions in the Cancer Control Module, some persons did not complete the supplement." However, whereas in 2000, persons who answered less than 50 percent of the questions in the supplement had a value of "not ascertained" automatically inserted in the appropriate fields of the Cancer Control Module file, in both 2005 and 2010, persons who answered none of the questions in the supplement had a value of "not ascertained" automatically inserted in the appropriate fields of the Cancer Control Module file.


  • 2000; 2005; 2010: Sample adults age 18+ whose son(s) ever had colon cancer.


  • 2000, 2005, 2010