Table 4.

Cohort studies reporting all cause and overdose mortality rate ratios comparing periods out and in opioid substitution treatment adjusted for confounding

Study	Confounding factors*				All cause mortality				Overdose mortality
	Patient demographics	Severity of drug use/treatment	Comorbidity		Unadjusted rate ratio	Adjusted rate ratio	Percentage change†		Unadjusted rate ratio	Adjusted rate ratio	Percentage change†
Methadone
Buster, 20027	Sex, race	Treatment modality, time since first treatment	—		—	—	—		0.87	0.87	−0.3
Davoli, 200732	Age, sex	Length of heroin use, heroin injection, previous overdose	HIV, psychiatric comorbidity		—	—	—		7.71	7.43	−3.6
Degenhardt, 20096	Age, sex, calendar year	—	—		1.91	1.88	−1.3		—	—	—
Cornish, 20108	Age, sex, calendar year	—	Medical comorbidity		2.83	3.27	15.5		—	—	—
Evans, 20159 ‡	Age, sex, race, education, employment, criminality, health coverage	Primary opioid, frequency and length of opioid use, non-opioid drug use	HIV, hepatitis C, tuberculosis, disability, medical comorbidity, psychiatric comorbidity		2.73	3.70	35.5		3.51	4.42	25.8
Nosyk, 201536 ‡	Age, sex, race, calendar year, region	No of previous treatment episodes	Time since HIV diagnosis, CD4 count, AIDS, antiretroviral therapy, medical comorbidity		3.04	2.94	−3.4		1.14	1.47	28.6
Cousins, 201637	Age, sex	Treatment supervision, methadone dose	Medical comorbidity		3.09	3.64	17.8		1.60	1.63	1.7
Buprenorphine
Cornish, 20108	Age, sex, calendar year	—	Medical comorbidity		1.41	1.64	16.8		—	—	—

*Baseline or time varying confounding factors used in adjustment.

†Percentage change in rate ratio after adjustment for corresponding confounding factors.

‡Overdose mortality rate ratios reported combining methadone maintenance with detoxification (11.4% of person years in treatment) in Evans et al,⁹ and including never treated participants (73.3% of person years out of treatment) in Nosyk et al.³⁶