Injecting drug users in Scotland, 2006: Listing, number, demography, and opiate-related death-rates

Figures & data

Table I.  Number of individuals observed: (a) in each combination of data-sources per demographic cross-classification; (b) by each demographic characteristic (GGC = Greater Glasgow & Clyde; Rest = rest of Scotland), or data-source (DS1 = social enquiry reports; DS2 = hospital records; DS3 = drug treatment agencies; DS4 = recent HCV diagnoses)

(a)
DS1	DS2	DS3	DS4	Male <35 GGC	Male 35+ GGC	Female <35 GGC	Female 35+ GGC	Male <35 Rest	Male 35+Rest	Female <35 Rest	Female 35+ Rest	Total
0	0	0	0	?	?	?	?	?	?	?	?	?
1	0	0	0	97	60	41	13	278	67	86	12	654
0	1	0	0	77	111	48	34	173	144	108	56	751
1	1	0	0	3	4	3	0	4	0	5	0	19
0	0	1	0	292	149	117	26	1379	431	584	114	3092
1	0	1	0	7	4	5	0	110	16	53	3	198
0	1	1	0	6	5	7	4	39	27	24	9	121
1	1	1	0	2	0	0	0	2	1	2	1	8
0	0	0	1	122	135	48	38	134	104	78	25	684
1	0	0	1	2	1	1	0	6	0	3	0	13
0	1	0	1	5	10	2	4	7	7	5	3	43
1	1	0	1	0	1	0	0	1	0	0	0	2
0	0	1	1	3	2	4	1	27	13	18	1	69
1	0	1	1	1	0	0	0	5	1	0	0	7
0	1	1	1	3	0	0	0	2	1	2	1	9
1	1	1	1	0	0	0	0	0	0	0	0	0
				620	482	276	120	2167	812	968	225
(b)
Summary statistics by data-source, or characteristic			DS1	DS2	DS3	DS4	Male	Female	<35	35+	GGC	Rest
IDUs observed			901	953	3504	827	4081	1589	4031	1639	1498	4172

Figure 1. Posterior probability distribution for Scotland's number of current injectors in 2006: by using all four data sources and by using three only.

Table II.  Posterior median [mean] and 95% “symmetric” CI rounded to nearest 100 for number of current IDUs, overall and per-stratum: M = male, F = female; 15–34 and 35 + denote age-groups

Current IDUs per stratum: to nearest 100	2006: all 4 data-sources		2006: having excluded recent HCV diagnoses
	Model-averaged median [mean]	95% CI	Model-averaged median [mean]	95% CI
M, 15–34, GGC	4200 [ 4300]	(3000,  6000)	3300 [ 3400]	(2600,  4900)
M, 35+, GGC	4500 [ 4600]	(3100,  6500)	2800 [ 2900]	(2100,  4400)
F, 15–34, GGC	1800 [ 1800]	(1200,  2600)	1300 [ 1300]	(1000,  2000)
F, 35+, GGC	1100 [ 1100]	( 700,  1600)	600 [  600]	( 400,  1000)
M, 15–34, Rest	9100 [ 9200]	(7100, 11300)	8200 [ 8400]	(6800, 11700)
M, 35+, Rest	5400 [ 5400]	(3800,  7000)	3900 [ 4000]	(3000,  5800)
F, 15–34, Rest	3900 [ 3900]	(3000,  4800)	3300 [ 3400]	(2700,  4700)
F, 35+, Rest	1300 [ 1300]	( 900, 1700)	900 [  900]	( 700,  1300)
Total	31500 [31700]	(24900, 38700)	24300 [25000]	(20700, 35000)

Table III.  Posterior median [mean] and 95% “symmetric” CI rounded to nearest 100 for the number of current IDUs per gender and age-group stratum in 2000, 2003, and 2006: 15–34 and 35+ denote the age-groups

Gender and age-group stratum in serial Bayesian CRC analyses	Model-averaged median for Scotland's current IDUs
	2000^ab (King et al., 2005)	2003^b (King et al., 2009)	2006: all four data-sources having excluded recent HCV diagnoses
			Median [mean]	95% CI
Male, 15–34	16000	13400	13400 [13500]	(10600, 16500)
			11500 [11800]	(9500, 16500)
Male, 35+	3300	5800	9900 [10000]	(7300, 12800)
			6700 [ 6900]	(5200, 10100)
Female, 15–34	6300	6500	5700 [ 5800]	(4500,  7000)
			4600 [ 4700]	(3700,  6600)
Female, 35+	800	1700	2400 [ 2400]	(1700,  3100)
			1500 [ 1600]	(1100,  2300)

Notes: ^aOutwith Greater Glasgow, four island and other health areas did not take part in the 2000 CRC study, to account for which a modest proportionate adjustment (by 1.15) was made by King et al. (2005). Also, only two CRC data-sources (social enquiry reports; recent HCV diagnoses) in 2000 were the same as in 2003 and 2006; and the numerator used was all DRDs rather than opiate-related DRDs.

^bThe estimates for 2000 and 2003 included the HCV database as a data source in the CRC analyses.

Table IV.  Posterior median [mean] and 95% “symmetric” CI by gender and age-group stratum for the annual opiate-related DRD rate per 100 current IDUs in 2006 – all 4 data-sources in play

Stratum	Current IDUs: model-averaged median [mean]: to nearest 10	Opiate-related DRDs in 2006 and 2007	Annual mean opiate-related DRD rate per 100 current IDUs (95% CI)
All Scotland: summary strata
15–34, female	5720 [ 5750]	57	0.50 (0.40, 0.62)
15–34, male	13440 [13530]	333	1.25 (0.99, 1.53)
35+ years, both sexes	12280 [12390]	306	1.24 (0.90, 1.59)
All Scotland: males
15–34	13440 [13530]	333	1.25 (0.99, 1.53)
35+ years	9900 [ 9990]	251	1.28 (0.94, 1.64)
All Scotland: females
15–34	5720 [ 5750]	57	0.50 (0.40, 0.62)
35+ years	2380 [ 2400]	55	1.17 (0.84, 1.52)
GGC: males
15–34	4180 [ 4330]	115	1.37 (0.91, 1.83)
35+ years	4450 [ 4600]	114	1.29 (0.82, 1.74)
GGC: females
15–34	1770 [ 1830]	26	0.73 (0.48, 0.98)
35+ years	1060 [ 1090]	26	1.24 (0.78, 1.71)
Rest of Scotland: males
15–34	9140 [ 9200]	218	1.20 (0.94, 1.50)
35+ years	5360 [ 5390]	137	1.30 (0.94, 1.71)
Rest of Scotland: females
15–34	3900 [ 3920]	31	0.40 (0.31, 0.50)
35+ years	1300 [ 1310]	29	1.14 (0.81, 1.51)

Table V.  Posterior median [mean] and 95% “symmetric” CI by gender and age-group stratum for the annual opiate-related DRD rate per 100 current IDUs in 2006 – after exclusion of recent HCV diagnoses (data-source DS4)

Stratum	Current IDUs: model-averaged median [mean]: to nearest 10	Opiate-related DRDs in 2006 and 2007	Annual mean opiate-related DRD rate per 100 current IDUs (95% CI) Also for 2003: from King et al. (2009)
All Scotland: summary strata
15–34, female	4600 [ 4720]	57	0.61 (0.43, 0.76)
			2003: 0.38 (0.31, 0.49)
15–34, male	11480 [11810]	333	1.43 (1.01, 1.75)
			2003: 0.98 (0.81, 1.25)
35+ years, both sexes	8180 [ 8480]	306	1.85 (1.24, 2.37)
			2003: 1.21 (0.95, 1.63)
All Scotland: males
15–34	11480 [11810]	333	1.43 (1.01, 1.75)
			2003: 0.98 (0.81, 1.25)
35+ years	6680 [ 6920]	251	1.86 (1.24, 2.40)
			2003: 1.22 (0.95, 1.64)
All Scotland: females
15–34	4600 [ 4720]	57	0.61 (0.43, 0.76)
			2003: 0.38 (0.31, 0.49)
35+ years	1500 [ 1560]	55	1.82 (1.19, 2.41)
			2003: 1.18 (0.91, 1.62)
GGC: males
15–34	3280 [ 3390]	115	1.74 (1.17, 2.21)
35+ years	2800 [ 2910]	114	2.02 (1.30, 2.67)
GGC: females
15–34	1310 [ 1350]	26	0.99 (0.66, 1.28)
35+ years	610 [  640]	26	2.12 (1.33, 2.91)
Rest of Scotland: males
15–34	8190 [ 8420]	218	1.32 (0.93, 1.60)
35+ years	3880 [ 4010]	137	1.75 (1.17, 2.25)
Rest of Scotland: females
15–34	3290 [ 3370]	31	0.47 (0.33, 0.58)
35+ years	890 [  920]	29	1.62 (1.08, 2.14)

Table A1.  Posterior probability of each two-way interaction, with its posterior mean (standard deviation) when present.

Interaction in 2006 vs. 2003	Posterior probability	Effect size: mean (SD)
Source-by-source
DS1 (social) × DS2 (hospital): lost significance	0.083	0.002 (0.017)
DS1 (social) × DS3 (DTA): effect doubled in 2006	1.000	0.193 (0.041)
DS1 (social) × DS4 (HCV)	0.079	0.000 (0.017)
DS2 (hospital) × DS3 (DTA): effect at least halved in 2006	0.700	0.068 (0.054)
DS2 (hospital) × DS4 (HCV)	0.998	0.212 (0.048)
DS3 (DTA) × DS4 (HCV)	0.087	−0.001 (0.017)
Covariate-by-covariate
Age (35+) × sex (female)	1.000	−0.144 (0.018)
Age (35+) × region (rest)	1.000	−0.134 (0.017)
Sex (female) × region (rest)	0.035	0.001 (0.004)
Source by covariate
DS1 (social) × age (35+)	1.000	−0.208 (0.030)
DS2 (hospital) × age (35+): acquired significance in 2006	0.912	0.075 (0.034)
DS3 (DTA) × age (35+)	1.000	−0.178 (0.027)
DS4 (HCV) × age (35+)	0.133	0.006 (0.021)
DS1 (social) × sex (female): lost significance in 2003	0.126	−0.005 (0.015)
DS2 (hospital) × sex (female): acquired significance in 2006	1.000	0.104 (0.020)
DS3 (DTA) × sex (female)	0.047	0.001 (0.007)
DS4 (HCV) × sex (female)	0.138	0.006 (0.017)
DS1 (social) × region (rest)	0.509	0.052 (0.062)
DS2 (hospital) × region (rest): lost significance in 2006	0.320	0.031 (0.051)
DS3 (DTA) × region (rest): acquired significance in 2006	1.000	0.247 (0.053)
DS4 (HCV) × region (rest)	0.768	−0.092 (0.057)

Notes: After exclusion of recent HCV diagnoses: Posterior marginal probabilities of the presence of each possible two-way interaction are shown in Table A2. From Table A1, two significant pairwise interactions, shown above in yellow, which involved recent HCV diagnoses became inadmissible in Table A2, where the only other change of note is further diminished importance for interaction between DS2 (hospital) and DS3 (DTA).

Table A2.  Having excluded DS4 (recent HCV diagnoses) as data-source, posterior probability of each two-way interaction, with its posterior mean (standard deviation) when present. DS1 = social enquiry reports; DS2 = hospital records; DS3 = drug treatment agencies

Interaction in 2006	Posterior probability	Effect size: mean (SD)
Source-by-source
DS1 (social) × DS2 (hospital)	0.139	−0.004 (0.024)
DS1 (social) × DS3 (DTA)	0.998	0.145 (0.043)
DS1 (social) × DS4 (HCV)	Inadmissible
DS2 (hospital) × DS3 (DTA)	0.207	0.013 (0.036)
DS2 (hospital) × DS4 (HCV)	Inadmissible
DS3 (DTA) × DS4 (HCV)	Inadmissible
Covariate-by-covariate
Age (35+) × sex (female)	1.000	−0.146 (0.020)
Age (35+) × region (rest)	1.000	−0.135 (0.019)
Sex (female) × region (rest)	0.057	0.001 (0.006)
Source by covariate
DS1 (social) × age (35+)	1.000	−0.164 (0.030)
DS2 (hospital) × age (35+)	0.974	0.131 (0.041)
DS3 (DTA) × age (35+)	1.000	−0.124 (0.040)
DS4 (HCV) × age (35+)	Inadmissible
DS1 (social) × sex (female)	0.121	−0.003 (0.013)
DS2 (hospital) × sex (female)	0.997	0.123 (0.020)
DS3 (DTA) × sex (female)	0.384	0.019 (0.029)
DS4 (HCV) × sex (female)	Inadmissible
DS1 (social) × region (rest)	0.299	0.016 (0.029)
DS2 (hospital) × region (rest)	0.096	0.001 (0.014)
DS3 (DTA) × region (rest)	1.000	0.211 (0.024)
DS4 (HCV) × region (rest)	Inadmissible

Notes: For the most part, interactions that were salient in 2003 were so also in 2006 with exceptions potentially reflecting changes in how current IDUs access services. Some of the changes, such as hospital listing, may be a consequence of the ageing of Scotland's IDU-population, others a reflection of regional variation in service delivery. We shall know more when the 2010 CRC analysis is complete so that a fourth pillar can be added to the demographic tallies of IDUs in Scotland in the twenty-first century.

King R, Bird SM, Brooks SP, Hutchinson SJ, Hay G. Prior information on behavioural capture–recapture methods: Demography influences injectors’ propensity to be listed on data sources and their drugs-related mortality. American Journal of Epidemiology 2005; 162: 694–703

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