Table 3.

Relative risks of mortality off opioid agonist treatment (OAT) versus on OAT (reference), according to key periods of opioid overdose public health emergency in British Columbia, Canada, 1 January 1996 to 30 September 2018

Period	Risk ratio (95% CI)
	Unadjusted	Adjusted*
Overall†	2.2 (2.1 to 2.4)	2.5 (2.1 to 2.9)
Period 1: before first death involving fentanyl ‡	1.8 (1.7 to 2.0)	2.1 (1.8 to 2.4)
Period 2: after first death involving fentanyl§	2.4 (2.2 to 2.7)	2.6 (2.1 to 3.2)
Period 3: after public health emergency declaration¶	3.1 (2.8 to 3.4)	3.4 (2.8 to 4.3)

Risk ratios compare crude mortality rate off OAT versus on OAT.

^*Adjusted for age, sex, medication type (buprenorphine/naloxone only, methadone only), OAT period (≤4 weeks or >4 weeks since starting or stopping OAT).

^†Entire follow-up period (1 January 1996 to 30 September 2018).

^‡Beginning of follow-up (1 January 1996) to day before first fentanyl related death in British Columbia (31 March 2012).

^§Date of first fentanyl related death in British Columbia (1 April 2012) to day before public health emergency declaration (13 April 2016)

^¶Date of emergency declaration (14 April 2016) to end of follow-up (30 September 2018).