The Influence of Smoking, Gender, and Family History on Colorectal Adenomas

Table 5

An ordered logistic regression model of smoking and adenoma occurrence among individuals (𝑛=5,395) undergoing screening colonoscopy in the New Hampshire Colonscopy Registry from 2004–2006.

	Increasing Size Category^a of
	Adenoma v. No Adenoma^b
Variable in fullmodel^c	Odds Ratio (95% CI)
Smoking
No pack-years	1.00 (referent)
15 pack-years or fewer	1.10 (0.89–1.34)
More than 15 pack-years	1.61 (1.34-1.93)^∗
Sex
Male	1.00 (referent)
Female	0.54 (0.46-0.63)^∗
Age (years)	1.02 (1.01-1.03)^∗
Family history^d
Negative	1.00 (referent)
Positive	1.69 (1.37-2.08)^∗

^aSize categories include <5 mm, 5–9 mm, ≥1 cm; odds ratios represent the proportional odds for the logit model. Thus, for one unit change in the predictor variable, the odds for cases in a group less than or equal to a given size category of polyp are the proportional odds times larger.
^bTest for assumption of proportionality of odds across response categories, using a likelihood ratio test, showed that the assumptions of the ordinal logistic regression were met (𝑃=.190).
^cResults reported are odds ratios for each variable in the model, adjusted for all other variables included in the model as shown here.
^dFamily history was defined as a reported diagnosis of colon or rectal cancer in a mother, father, sibling, or child of the patient.
^∗𝑃<.001.