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Table 1 Characteristics of study participants; bivariate and full multivariate linear regressionsa, (N = 811)

From: Comparison of subset selection methods in linear regression in the context of health-related quality of life and substance abuse in Russia

Independent variables n (%)b Bivariate OLS regression Full multivariate OLS regression (N = 803)c
Beta 95 % CI Beta 95 % CI
I. SOCIO-DEMOGRAPHIC CHARACTERISTICS
Sex:      
 Male 631 (77.8) Ref - Ref -
 Female 180 (22.2) 1.72 (−0.62 ; 4.06) −3.25 (−5.61 ; −0.88)
Age (median = 32 y.o):      
 Less than 32 y.o. 397 (49.0) Ref - Ref -
 32 y.o. or older 414 (51.0) −5.21 (−7.27 ; −3.14) −4.81 (−6.69 ; −2.93)
Education:      
 Primary or basic 62 (7.6) Ref - Ref -
 Secondary, vocational or at least some higher 749 (92.4) 7.37 (2.89 ; 11.84) 3.54 (−0.61 ; 7.68)
Main source of income:      
 Legal source 677 (83.5) Ref - Ref -
 Illegal source 134 (16.5) −3.27 (−5.78 ; −0.76) −0.35 (−2.75 ; 2.05)
Level of income:      
 Coping well 245 (30.2) Ref - Ref -
 Coping is difficult (or very difficult) 566 (69.8) −8.99 (−11.18 ; −6.80) −3.86 (−6.00 ; −1.73)
Living arrangements:      
 Someone else’s house 274 (33.8) Ref - Ref -
 Owned or rented place 512 (63.1) −3.24 (−5.35 ; −1.13) 1.73 (−0.33 ; 3.79)
 Shelter/no fixed place 25 (3.1) −5.00 (−10.80 ; 0.81) 0.97 (−4.74 ; 6.69)
Marital status:d      
 Not married 554 (68.4) Ref - Ref -
 Married 256 (31.6) −0.21 (−2.55 ; 2.13) −0.96 (−3.40 ; 1.49)
II. ALCOHOL AND DRUG USE
Alcohol abuse using CAGE scale:      
 CAGE = 0–1 274 (33.9) Ref - Ref -
 CAGE = 2-4 534 (66.1) −10.10 (−12.20 ; −8.00) −1.76 (−4.00 ; 0.47)
Age of first drug use (cannabis excluded; median = 16 y.o.):      
 17 y.o. or older 280 (34.5) Ref - Ref -
 16 y.o. or younger 531 (65.5) −6.64 (−8.70 ; −4.58) −3.38 (−5.47 ; −1.30)
Main drug of use:      
 (Meth)-amphetamines 27 (3.3) Ref - Ref -
 Methadone/Fentanyl 221 (27.3) −6.92 (−11.80 ; −2.04) 1.43 (−3.51 ; 6.37)
 Heroin 563 (69.4) −14.74 (−19.39 ; −10.08) 0.87 (−4.01 ; 5.74)
Poly-drug use in the last 4 weeks:e      
 Injected 1 class of drugs 697 (85.9) Ref - Ref -
 Injected 2 or more classes of drugs 114 (14.1) −6.15 (−9.08 ; −3.22) −3.62 (−6.38 ; −0.87)
Frequency of injecting drugs (days during the last 4 weeks; median = 20):      
 19 days or less 337 (41.6) Ref - Ref -
 20 days or more 474 (58.4) −8.37 (−10.49 ; −6.25) −1.39 (−3.88 ; 1.09)
Frequency of injecting drugs (times per day; median = 1):      
 One 437 (54.0) Ref - Ref -
 Two or more 372 (46.0) −7.69 (−9.79 ; −5.60) −0.40 (−2.61 ; 1.80)
Used non-sterile injecting equipment at least once in the last 4 weeks:      
 No (or don’t know) 344 (42.4) Ref - Ref -
 Yes 467 (57.6) −10.54 (−12.59 ; −8.50) −2.05 (−4.41 ; 0.30)
Ever used non-sterile injecting equipment:      
 No 79 (9.7) Ref - Ref -
 Yes 732 (90.3) −10.94 (−14.08 ; −7.81) −0.55 (−4.13 ; 3.04)
Getting sterile injecting equipment (any unused syringes in last 4 weeks):      
 No 46 (5.7) Ref - Ref -
 Yes 765 (94.3) 9.12 (4.77 ; 13.48) −0.97 (−5.14 ; 3.20)
Ever overdosed:      
 No 284 (35.0) Ref - Ref -
 Yes 527 (65.0) −6.58 (−8.75 ; −4.42) 0.10 (−2.12 ; 2.32)
III. MENTAL HEALTH
Mental health problems score:      
 Lower score on mental health problems 427 (52.7) Ref - Ref -
 Higher score on mental health problems 384 (47.3) −9.27 (−11.28 ; −7.26) −2.61 (−4.85 ; −0.38)
IV. SEXUAL RISK
Sexually active in the last 6 months:      
 No 188 (23.2) Ref - Ref -
 Yes 623 (76.8) 1.75 (−0.73 ; 4.23) 0.91 (−1.69 ; 3.52)
Involved in sexual work in the last 6 months:      
 No 757 (93.3) Ref - Ref -
 Yes 54 (6.7) −0.16 (−3.35 ; 3.03) 2.80 (−1.05 ; 6.66)
Paid for sex in the last 6 months:      
 No 748 (92.2) Ref - Ref -
 Yes 63 (7.8) 7.80 (4.65 ; 10.95) 2.25 (−1.11 ; 5.60)
Condom use during the last sexual intercourse:      
 Yes 378 (46.6) Ref - N/A -
 No 238 (29.3) −0.79 (−3.29 ; 1.72)   
 Don’t know 195 (24.0) −2.44 (−5.11 ; 0.24)   
HIV and Hepatitis C status of primary sexual partner:      
 HIV and HCV negative or unknown 155 (19.1) Ref - Ref -
 Known to be HIV or HCV positive 218 (26.9) −11.09 (−14.14 ; −8.04) −1.98 (−5.05 ; 1.09)
 No primary partner in the last 6 months 438 (54.0) −8.23 (−11.00 ; −5.47) −2.02 (−5.04 ; 1.00)
V. INFECTIOUS DISEASES HISTORY AND STATUS
Ever been tested for HIV:      
 No (or don’t know) 52 (6.4) Ref - Ref -
 Yes 759 (93.6) −1.95 (−6.04 ; 2.13) 3.63 (−0.58 ; 7.84)
HIV status awareness:      
 Result of the most recent HIV test is negative, unknown or never tested 428 (52.8) Ref - N/A -
 Result of the most recent HIV test is positive 383 (47.2) −9.71 (−11.74 ; −7.68)   
HIV status (based on study testing):      
 Negative 359 (44.3) Ref - Ref -
 Positive 452 (55.7) −9.20 (−11.26 ; −7.15) −2.71 (−6.55 ; 1.13)
Receiving regular HIV care:      
 HIV-negative or unaware 428 (52.8) Ref - Ref -
 HIV+; receives regular HIV care 125 (15.4) −0.87 (−3.41 ; 1.67) 1.46 (−3.05 ; 5.98)
 HIV+; does not receive regular HIV care 258 (31.8) −13.77 (−15.95 ; −11.59) −4.32 (−8.36 ; −0.28)
Tuberculosis history awareness:      
 No (or don’t know) 757 (93.3) Ref - Ref -
 Yes 54 (6.7) −7.46 (−11.15 ; −3.76) −3.32 (−6.43 ; −0.22)
Hepatitis C history awareness:      
 No 126 (15.5) Ref - N/A -
 Yes 685 (84.5) −10.13 (−13.02 ; −7.23)   
Treatment of Hepatitis C:      
 Never diagnosed with HCV 126 (15.5) Ref - Ref -
 HCV+, never been offered treatment 591 (72.9) −11.09 (−14.00 ; −8.17) −4.56 (−7.62 ; −1.50)
 HCV+, was offered treatment, but did not receive it 50 (6.2) −7.45 (−12.58 ; −2.32) −7.37 (−12.75 ; −1.99)
 HCV+, was offered treatment and received it 44 (5.4) −0.27 (−4.53 ; 3.98) −2.02 (−6.80 ; 2.76)
Hepatitis B history awareness:      
 No 401 (49.4) Ref - Ref -
 Yes 410 (50.6) −9.31 (−11.29 ; −7.34) −0.05 (−2.36 ; 2.25)
Ever vaccinated against Hepatitis B:      
 No (or don’t know) 525 (64.7) Ref - Ref -
 Yes (at least one dose) 286 (35.3) 7.29 (5.07 ; 9.50) 1.63 (−0.74 ;4.00)
VI. CONTACT WITH TREATMENT SERVICES AND PRISON
History of incarceration:      
 No 537 (66.2) Ref - Ref -
 Yes 274 (33.8) −2.41 (−4.64 ; −0.18) −1.49 (−3.40 ; 0.42)
Having basic medical insurance:      
 No 156 (19.3) Ref - Ref -
 Yes 654 (80.7) 2.39 (−0.40 ; 5.17) 1.46 (−1.06 ; 3.98)
Receiving any healthcare services in the last 12 months:      
 Received 546 (67.3) Ref - Ref -
 Not received 265 (32.7) −3.00 (−5.32 ; −0.68) −1.46 (−3.56 ; 0.64)
Ever received drug abuse treatment:      
 No 229 (28.2) Ref - N/A -
 Yes 582 (71.8) −5.79 (−8.15 ; −3.43)   
Receiving detoxification services in the last 6 months:      
 Did not need detox services 646 (79.7) Ref - Ref -
 Needed, but did not receive detox 99 (12.2) −10.74 (−14.12 ; −7.35) −5.39 (−9.00 ; −1.78)
 Needed and received detox 66 (8.1) −4.00 (−8.04 ; 0.04) −4.82 (−7.96 ; −1.67)
Ever had difficulties obtaining drug abuse treatment:      
 Never received treatment (or don’t know) 233 (28.7) Ref - Ref -
 Had no difficulties 482 (59.4) −4.44 (−6.89 ; −1.99) 1.26 (−0.93 ; 3.45)
 Had difficulties 96 (11.8) −10.56 (−13.92 ; −7.20) −0.74 (−4.14 ; 2.66)
Had difficulties obtaining medical care because of drug use:      
 No (or don’t know) 764 (94.2) Ref - Ref -
 Yes 47 (5.8) −5.10 (−9.48 ; −0.73) −4.22 (−8.21 ; −0.22)
VII. STIGMA, DISCLOSURE AND POLICE HARASSMENT
Ever experienced police confiscate syringes:      
 No 599 (73.9) Ref - Ref -
 Yes 212 (26.1) −6.00 (−8.41 ; −3.59) −0.48 (−3.02 ; 2.06)
PWID status disclosure to family/friends:f      
 Rather disclosed 420 (51.8) Ref - Ref -
 Rather did not disclose 391 (48.2) −7.06 (−9.10 ; −5.01) −0.65 (−2.78 ; 1.48)
PWID status disclosure to a healthcare provider:g      
 Rather disclosed 278 (34.3) Ref - Ref -
 Rather did not disclose 533 (65.7) 3.83 (1.67 ; 5.99) −0.16 (−2.51 ; 2.19)
Internalized PWID stigma:h      
 Low 417 (51.4) Ref - Ref -
 High 394 (48.6) −9.14 (−11.15 ; −7.13) −3.68 (−5.92 ; −1.44)
PWID stigma consciousness:h      
 Low 343(42.3) Ref - Ref -
 High 468 (57.7) −1.68 (−3.81 ; 0.45) 1.52 (−0.52 ; 3.56)
  1. 95 % CI 95 % confidence interval, HRQoL Health-related quality of life, OLS Ordinary Least Squares, PWID people who inject drugs, Ref Reference Category, VAS Visual Analogue Scale
  2. aDependent Variable is EuroQoL 5D VAS measure of the HRQoL
  3. bNumbers may not sum up to total due to missing values, and % may not sum up to 100 due to rounding
  4. cThe adjusted R2 = 0.37. Four variables (Condom use during the last sexual intercourse, HIV status awareness, Hepatitis C awareness, Ever received drug abuse treatment) were not included into the multivariate regression, because of complete collinearity with other variables in the model
  5. dMarried = legally married or living as married; Not married = widowed, divorced or never married
  6. eThe following classes of drugs are included: opiates, amphetamines, and cocaine
  7. fBased on five questions, each measured on 5-point Likert scale. Individual items scores were summed and dichotomized by median
  8. gBased on one question measured on 5-point Likert scale, and dichotomized by median
  9. hBoth internalized stigma scale and stigma consciousness scale are six items questionnaires measured on the 5-point Likert scale. Individual items scores were summed and dichotomized by median
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BMC Medical Research Methodology

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