Table 2

Univariate regression of saliva cotinine (dependent variable) on presumed measures of exposure to cigarette smoke (independent variables), among 98 smokers and 85 daily smokers who provided a saliva sample and were not currently using nicotine replacement products

Measures of exposure (independent variables)		All smokers				Daily smokers
Measures of exposure (independent variables)		Regression coefficient^2-151	r²^2-152			Regression coefficient^2-151	r²^2-152
Cigarettes per day	7.3^2-165	0.359		5.7^2-165	0.250
Cig/day, with values >25 set to 25	16.0^2-165	0.527		14.7^2-165	0.379
Number of butts	7.2^2-165	0.326		5.5^2-165	0.229
Puffs per cigarette	2.0 (NS)	0.004		2.5 (NS)	0.008
Intensity of smoking (0–100 rating)	3.9^2-165	0.397		3.8^2-165	0.356
Self reported nicotine yield (mg)	142.6^2-150	0.058		144.5^2-150	0.072
Nicotine yield on pack (mg)	147.6^2-150	0.065		150.4^2-150	0.080
Self reported tar yield (mg)	11.5^2-160	0.067		12.1^2-160	0.088
Tar yield on pack (mg)	11.4^2-150	0.067		11.3^2-150	0.066
Type of cigarettes (regular + mild + hand rolled versus light + ultralight)	73.5^2-150	0.047		54.3 (NS)	0.031
Self reported length of butts (mm)	−1.5 (NS)	0.004		−3.7 (NS)	0.027
Actual length of butts (mm)	−4.0 (NS)	0.022		−4.1 (NS)	0.029
Colour, end of the filter (0–10 scale)	19.4^2-150	0.054		12.6 (NS)	0.025
Inhalation (1–5 scale)	32.5 (NS)	0.030		12.6 (NS)	0.005
Quantity of smoke (0–10 scale)	41.5^2-165	0.268		32.8^2-165	0.160
Minutes to first cig in the morning	−0.7^2-165	0.298		−0.8^2-165	0.197
Fagerström dependence test (FTND)	41.1^2-165	0.406		33.2^2-165	0.302
FTND items:
1 Minutes to first cig (in four categories)	94.2^2-165	0.355		79.2^2-165	0.282
2 Difficult to refrain	152.6^2-165	0.121		113.9^2-160	0.089
3 Cig hate most to give up	43.6 (NS)	0.016		38.3 (NS)	0.014
4 Cig per day (in four categories)	119.3^2-165	0.407		95.7^2-165	0.290
5 Morning smoking	130.9^2-165	0.126		100.3^2-160	0.092
6 Smoke if ill	157.8^2-165	0.154		117.9^2-160	0.112
Predicted value from four item model	1.0^2-165	0.639		1.0	0.526

Statistical significance:
↵2-150 p⩽0.05;
↵2-160 p⩽0.01;
↵2-165 p⩽0.001. NS: not statistically significant.
↵2-151 Coefficients of linear regression indicate the change in cotinine (in ng/ml) for an increase of one unit in the independent variable.
↵2-152 r ² statistics from linear regression models indicate the proportion of variance in saliva cotinine explained by independent variables.