. 2017 Oct 1;179:309–316. doi: 10.1016/j.drugalcdep.2017.07.024

Table 3.

Results of Generalised Estimating Equation analysis comparing historical offending rates of opiate users and non-users using whole sample (Model 1, N = 97,803) and those with complete data on age of initiation of opiate use (Model 2, N = 91,565), separately for males and females and for four categories of offences.

		Male				Female
		Model 1^b		Model 2^c		Model 1^b		Model 2^c
Offence category	Variable	RR	95% CI	RR	95% CI	RR	95% CI	RR	95% CI
All crimes	Opiate users vs. non-users	1.99	[1.96, 2.01]	–	–	4.59	[4.48, 4.69]	–	–
	Initiation of opiate use	–	–	1.16	[1.15, 1.17]	–	–	2.00	[1.95, 2.05]
	Users (pre-onset) vs. non-users	–	–	2.00	[1.97, 2.03]	–	–	2.80	[2.71, 2.90]
	Users (post-onset) vs. non-users	–	–	2.32	[2.29, 2.35]	–	–	5.61	[5.47, 5.75]
	Age^a	1.92	[1.92, 1.93]	1.90	[1.90, 1.91]	2.53	[2.51, 2.55]	2.32	[2.30, 2.34]
	Age-squared^a	0.77	[0.77, 0.78]	0.77	[0.77, 0.77]	0.78	[0.78, 0.78]	0.79	[0.79, 0.79]
	Age-cohort
	<1975	0.75	[0.74, 0.76]	0.74	[0.73, 0.75]	0.62	[0.60, 0.64]	0.68	[0.66, 0.70]
	1975–1979	0.86	[0.85, 0.87]	0.85	[0.84, 0.86]	0.78	[0.76, 0.80]	0.82	[0.79, 0.84]
	1980–1984	Ref		Ref		Ref		Ref
	1985+	1.32	[1.30, 1.34]	1.33	[1.31, 1.35]	1.76	[1.71, 1.82]	1.71	[1.65, 1.76]

Non-serious acquisitive	Opiate users vs. non-users	2.65	[2.61, 2.69]	–	–	4.79	[4.66, 4.91]	–	–
	Initiation of opiate use	–	–	1.72	[1.69, 1.75]	–	–	2.18	[2.11, 2.25]
	Users (pre-onset) vs. non-users	–	–	1.97	[1.92, 2.02]	–	–	2.73	[2.62, 2.85]
	Users (post-onset) vs. non-users	–	–	3.39	[3.34, 3.45]	–	–	5.95	[5.78, 6.12]
	Age	1.85	[1.84, 1.85]	1.74	[1.73, 1.75]	2.46	[2.43, 2.48]	2.23	[2.20, 2.25]
	Age-squared	0.83	[0.83, 0.83]	0.83	[0.83, 0.83]	0.76	[0.76, 0.77]	0.78	[0.77, 0.78]
	Age-cohort
	<1975	0.87	[0.85, 0.89]	0.92	[0.90, 0.93]	0.80	[0.78, 0.83]	0.90	[0.87, 0.93]
	1975–1979	0.95	[0.93, 0.97]	0.96	[0.94, 0.98]	0.88	[0.85, 0.91]	0.93	[0.89, 0.96]
	1980–1984	Ref		Ref		Ref		Ref
	1985+	1.08	[1.05, 1.10]	1.05	[1.02, 1.07]	1.30	[1.25, 1.35]	1.26	[1.21, 1.32]

Serious acquisitive	Opiate users vs. non-users	1.84	[1.81, 1.87]	–	–	4.11	[3.85, 4.38]	–	–
	Initiation of opiate use	–	–	1.25	[1.22, 1.27]	–	–	1.76	[1.62, 1.92]
	Users (pre-onset) vs. non-users	–	–	1.87	[1.82, 1.91]	–	–	3.16	[2.88, 3.46]
	Users (post-onset) vs. non-users	–	–	2.33	[2.27, 2.38]	–	–	5.58	[5.19, 6.00]
	Age^a	1.16	[1.15, 1.16]	1.11	[1.11, 1.12]	1.39	[1.36, 1.42]	1.27	[1.23, 1.30]
	Age-squared^a	0.66	[0.66, 0.66]	0.65	[0.64, 0.65]	0.81	[0.80, 0.82]	0.81	[0.80, 0.83]
	Age-cohort
	<1975	0.83	[0.81, 0.84]	0.73	[0.71, 0.75]	0.75	[0.69, 0.82]	0.84	[0.77, 0.93]
	1975–1979	1.40	[1.37, 1.43]	1.39	[1.36, 1.42]	0.83	[0.76, 0.91]	0.90	[0.82, 0.99]
	1980–1984	Ref		Ref		Ref		Ref
	1985+	1.05	[1.02, 1.07]	1.06	[1.04, 1.09]	1.44	[1.31, 1.57]	1.46	[1.33, 1.61]

Violent offences	Opiate users vs. non-users	1.39	[1.36, 1.42]	–	–	2.42	[2.30, 2.55]	–	–
	Initiation of opiate use	–	–	0.75	[0.72, 0.77]	–	–	1.04	[0.96, 1.13]
	Users (pre-onset) vs. non-users	–	–	1.79	[1.72, 1.85]	–	–	2.51	[2.31, 2.72]
	Users (post-onset) vs. non-users	–	–	1.34	[1.30, 1.37]	–	–	2.61	[2.45, 2.77]
	Age^a	1.85	[1.84, 1.87]	1.91	[1.89, 1.93]	1.79	[1.76, 1.83]	1.80	[1.75, 1.84]
	Age-squared^a	0.80	[0.80, 0.81]	0.80	[0.80, 0.80]	0.88	[0.87, 0.89]	0.88	[0.87, 0.89]
	Age-cohort
	<1975	0.71	[0.69, 0.73]	0.67	[0.65, 0.69]	0.43	[0.40, 0.47]	0.44	[0.41, 0.48]
	1975–1979	0.71	[0.69, 0.73]	0.69	[0.67, 0.71]	0.60	[0.56, 0.65]	0.61	[0.56, 0.65]
	1980–1984	Ref		Ref		Ref		Ref
	1985+	1.87	[1.82, 1.92]	1.92	[1.86, 1.97]	2.53	[2.38, 2.70]	2.59	[2.43, 2.78]

See Appendix D (Supplementary material) for rate within years.

Age: per five year change.

Model 1 calculates the rate ratio, comparing the historical offences of opiate users with non-users, controlling for all other variables in table.

Model 2 includes linked data on age of opiate initiation, to model the effect of opiate initiation on the offending Rate Ratio. This allows the comparison of opiate users and non-users both prior to and post- opiate initiation.