Table 2.

Cox proportional hazards model of time to initiating methamphetamine injection among a cohort of injection drug users (n = 1317)

Characteristic	Unadjusted HR* (95% CI)	p-value	Adjusted HR* (95% CI)	p-value
Age (per year older)	0.96 (0.95–0.98)	<0.001	0.96 (0.95–0.98)	<0.001
Sex (female vs. male)	0.86 (0.64–1.14)	0.291	0.58 (0.41–0.82)	0.002
Ethnicity (Caucasian vs. other)	1.22 (0.92–1.61)	0.173
Relationship Status (married vs. single/dating)	0.63 (0.42–0.93)	0.019
Sexual Orientation (LGBTa vs. heterosexual)	0.86 (0.52–1.44)	0.576
Sexual Abuse‡ (yes vs. no)	1.44 (1.08–1.90)	0.012	1.63 (1.18–2.23)	0.004
Age of First Injection (per year older)	0.98 (0.96–0.99)	0.016
Buy Drugs in DTESc† (yes vs. no)	2.40 (1.71–3.36)	<0.001
Use Drugs in DTESc† (yes vs. no)	2.78 (1.97–3.92)	<0.001	2.15 (1.49–3.10)	<0.001
Homeless† (yes vs. no)	2.34 (1.68–3.25)	<0.001	1.43 (1.01–2.04)	0.047
Non-injection Crack Use† (yes vs. no)	3.14 (2.11–4.67)	<0.001	2.06 (1.36–3.14)	0.001
Non-injection MAb Use† (yes vs. no)	4.54 (2.52–8.16)	<0.001	3.69 (2.03–6.70)	<0.001
Injection Heroin Use† (yes vs. no)	2.15 (1.59–2.89)	<0.001
Injection Cocaine Use† (yes vs. no)	1.71 (1.24–2.35)	0.001
Inject with a Sex Partner† (yes vs. no)	1.17 (0.77–1.76)	0.463
Inject with a Friend† (yes vs. no)	1.82 (1.35–2.44)	<0.001
Syringe Sharing† (yes vs. no)	1.75 (1.07–2.85)	0.025
Warrant or Area Restriction¶ (yes vs. no)	2.02 (1.35–3.00)	0.001
Methadone Maintenance Therapy¶ (yes vs. no)	0.89 (0.66–1.21)	0.463
Inject while Incarcerated† (yes vs. no)	3.93 (0.97–15.91)	0.055

^*HR=Hazard Ratio

^aLGBT=lesbian, gay, bisexual, transgender/transsexual

^bMA=methamphetamine

^cDTES=Downtown Eastside

^†refers to activities in the past 6 months

^‡refers to lifetime experiences

^¶refers to current experiences.

Note: Variable selection based on AIC and type III p-values as described in (Lima et al., 2008).