Skip to main content
. Author manuscript; available in PMC: 2018 Mar 1.
Published in final edited form as: Epidemiology. 2017 Mar;28(2):266–274. doi: 10.1097/EDE.0000000000000609

Table 1.

Summary of covariate models.

Variable Type of model when used as
dependent variable		 Functional form when
used as predictor
Non-modifiable
  Gender Not predicted Indicator
  Age Not predicted Quadratic linear
  Height Not predicted Quadratic linear
  Education level Not predicted Six categoriesa
  Occupation Not predicted Six categoriesa
  Marital status Not predicted Three categoriesb
  Baseline smoking Not predicted Three categoriesb
Modifiable
  SBP Linear Quadratic linear
  Smoking Logistic then log-linearc Quadratic linear
  Cholesterol Linear Quadratic linear
  Anti-hypertension
  drug		 Linear Three categoriesb
a

Education level categories are ≤ 8th grade, some high school, high school graduate, some college, college graduate, and post-graduate. Occupation categories are executive/supervisory, technical, laborer, clerical, sales, and housewife.

b

Marital status categories are single, married, and divorce or widowed. Baseline smoking are smoking, not smoking, and quitting. Anti-hypertension drug are regular use, not use, and sporadic use.

c

zero-continuous variables such as cigarettes per day are predicted in two stages, first a logistic regression on an indicator of whether the variable is nonzero and then a linear regression of the log of the nonzero values.