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Table 4 Average increase in cotinine concentration (ng/ml) in adult daily smokers per one cigarette smoked in the previous 24 hours by type of regression model.

From: Salivary cotinine concentrations in daily smokers in Barcelona, Spain: a cross-sectional study

Estimation of model

β *

95% CI

R 2

p-value

Men (n = 103)

    

simple linear model

5.3

3.5, 7.2

0.244

----

quadratic model

15.7

9.0, 22.3

0.313

< 0.05

quadratic model adjusted for covariates

14.8

8.1, 21.5

0.353

< 0.05

Women (n = 104)

    

simple linear model

7.7

5.9, 9.5

0.412

----

quadratic model

11.2

5.7, 16.7

0.421

0.188

quadratic model adjusted for covariates

11.3

5.8, 16.7

0.458

0.078

  1. Barcelona (Spain), 2004-2005.
  2. β for the simple variable "number of cigarettes smoked in previous 24 hours" (for one cigarette smoked)
  3. p-value for the change of fit between the adjusted models and the simple linear model adjusted for age, educational level, and body mass index