Table 2.

Multivariable analysis of factors associated with methamphetamine use among people who inject drugs in Iran (2019–2020)

Variables	Adjusted odds ratio (95% CI)	P-value
History of homelessness (L12Ma)
Yes	1.57 (1.77, 2.10)	0.001
No	Ref
Age at first drug use (any type)
< 18 years old	1.40 (1.05, 1.87)	0.020
≥ 18 years old	Ref
Duration of injectionab
≥ 10 years	1.47 (1.11, 1.95)	< 0.001
< 10 years	Ref
Non-injection illicit opioids use (L3Mc)
Yes	7.18 (4.93, 10.47)	< 0.001
No	Ref
Injecting illicit opioids use (L3Mc)
Yes	2.98 (2.03, 4.36)	< 0.001
No	Ref
Multiple sex partners (L12Ma)
Yes	1.60 (1.50, 2.73)	< 0.001
No	Ref
Region
Central	1.15 (0.70, 1.89)	0.585
North	5.42 (2.92, 10.03)	< 0.001
South	2.95 (2.04, 4.27)	< 0.001
East	24.43 (15.62, 38.22)	< 0.001
West	Ref

^aLast 12 months

^bWhile this variable showed collinearity with age, we retained duration of injection because it represents a more direct measure of cumulative exposure to injection-related risks and environmental vulnerabilities that can influence methamphetamine use patterns. Unlike chronological age, injection career length better captures the accumulated effects of high-risk injection environments, unsafe practices, and structural vulnerabilities that are known to shape

^cLast three months