Table 2.

Hazard rate ratios (and 95% CIs) for incident venous thromboembolism (VTE) associated with traffic density, ARIC, 1987-2005 (n=13,143)

	Quartiles					Continuous variable (log-transformed)
	1 (lowest)	2	3	4	p value for trend *	One unit increase	p value
Median of quartiles	0	2.92	15.00	41.91
No. of cases/subjects	97/3,285	107/3,286	90/3,287	111/3,285
Basic model †	1.00	1.18 (0.89, 1.57)	0.98 (0.72, 1.32)	1.16 (0.88, 1.54)	0.53	1.01 (0.98, 1.03)	0.49
Adjusted model ‡	1.00	1.18 (0.88, 1.57)	0.99 (0.74, 1.34)	1.14 (0.86, 1.51)	0.64	1.01 (0.98, 1.03)	0.51

^*p values for trend based on quartiles scaled by the quartile medians.

^†Covariates included age, sex, center and ethnicity.

^‡Covariates included age, sex, center, ethnicity, BMI, diabetes status, factor VIII, aPTT, active and passive smoking, alcohol intake and background air pollution level.