Modeling predictors of risky drug use behavior among male street laborers in urban Vietnam
© Nguyen et al.; licensee BioMed Central Ltd. 2013
Received: 2 June 2012
Accepted: 2 May 2013
Published: 7 May 2013
The application of theoretical frameworks for modeling predictors of drug risk among male street laborers remains limited. The objective of this study was to test a modified version of the IMB (Information-Motivation-Behavioral Skills Model), which includes psychosocial stress, and compare this modified version with the original IMB model in terms of goodness-of-fit to predict risky drug use behavior among this population.
In a cross-sectional study, social mapping technique was conducted to recruit 450 male street laborers from 135 street venues across 13 districts of Hanoi city, Vietnam, for face-to-face interviews. Structural equation modeling (SEM) was used to analyze data from interviews.
Overall measures of fit via SEM indicated that the original IMB model provided a better fit to the data than the modified version. Although the former model was able to predict a lesser variance than the latter (55% vs. 62%), it was of better fit. The findings suggest that men who are better informed and motivated for HIV prevention are more likely to report higher behavioral skills, which, in turn, are less likely to be engaged in risky drug use behavior.
This was the first application of the modified IMB model for drug use in men who were unskilled, unregistered laborers in urban settings. An AIDS prevention program for these men should not only distribute information and enhance motivations for HIV prevention, but consider interventions that could improve self-efficacy for preventing HIV infection. Future public health research and action may also consider broader factors such as structural social capital and social policy to alter the conditions that drive risky drug use among these men.
KeywordsVietnam Drug use Risk Behavior(s) HIV/AIDS Unskilled Laborer(s) IMB Model Structural Equation Modeling (SEM)
Vietnam is one of a few countries in Asia and the Pacific region that is experiencing an exponential increase of HIV/AIDS among at-risk, drug-using populations . The first case of HIV was reported in 1990 in Hochiminh City, but then rapidly increased among injection drug users (IDU). By 1999, 63 provinces reported more than 16,149 HIV-positive cases, of which 65% were IDU . The same was also true in the most recent national data reporting that there have been 160,019 reported HIV cases and 44,050 deaths due to AIDS-related illnesses by the end of 2009, most (82.5%) were males with an overwhelming majority as IDU .
Although the HIV epidemic is primarily associated with injection drug use, its extent is highly variable across the country. In the cities of Hochiminh, Can Tho, Hai Phong, Thai Nguyen, and Quang Ninh, for instance, the HIV rate among IDU was over 40% . In Hanoi, the first HIV infection was reported in 1993, but then increased rapidly among IDU from 3.3% in 1998 to 13.3% in 1999, 17.5% in 2000 , and 20.8% in 2008 .
Compared with nonmigrant populations, migrants are more vulnerable to risk behaviors for HIV. The separation from family, social disruption, breakdown of social networks, lack of social control and support and anonymity of urban living created opportunities for risk behaviors – substance abuse and risky sexual behaviors - placing them at particular risk for HIV infection . A literature review by Voyer et al.  suggests that the variables of ethnicity, gender, marital status, mental health status, health perception, social support and access to health services were associated with drug use in most studies. According to Yang and Luo [5, 7], in addition to migrants’ individual characteristics, such as education, marital status, and psychosocial well-being, that seem to have predisposed them to drug misuse, exposure to the social influence of drug-using peers, friends, or relatives in their social network may also facilitate migrants to take drugs. Whether drug use is examined separately or jointly with other risk behaviors, psychosocial well-being and behavior-specific social influences as measured in many studies are all significant risk factors, and their impacts are frequently consistent with the literature. Until now, although sexual risk behaviors among migrants have received greater attention, little is known about drug use behavior and its associated factors among this population .
In response to several of these recommendations, a recent qualitative study was conducted on this population which aimed to explore lived experiences of male migrants who served in informal sectors – performing unskilled, unregistered, and low-income labors within an urban setting of Vietnam . The results highlighted some important social factors that placed these men at risk of HIV transmission. Family and community pressure, expectations and limited employment options in rural areas frustrated and compelled them to migrate great distances to the city for informal work. However, working in urban settings generated numerous stressors for these men, compelling them to seek out a range of coping strategies, such as sex and drug uptake. Risk behaviors for acquiring HIV, including unsafe sex and injection drug use, were more likely in men who had misperceptions of HIV/AIDS and experienced psychological stresses such as tedium, boredom, depression, fatalism, revenge, and family and social pressure as well as alcohol consumption than in other men. However, a key gap in the literature is a lack of quantitative research that can be statistically tested in order to validate previous qualitative findings and to identify the extent to what various factors have been considered to influence drug use behavior among this population.
The constructs of the original and modified IMB model
Number of items
The original model
HIV preventive information
HIV preventive motivation
HIV preventive behavioral skills
Skill 1 (preparation)
Skill 2 (practice)
The modified model
3 constructs of the original model
The main site for this study was the city of Hanoi, located in Northern Vietnam. The current population is now 6.5 million. Hanoi is one of the cities with the highest HIV/AIDS prevalence in adults within Vietnam . With its large area, industry and services, Hanoi is also one of the two largest cities in Vietnam and one of the most frequent choices for unkilled laborers, migrant laborers, and rural–urban migrants.
Sample size and participants
Survey procedures and ethics considerations
The research instrument was first validated on a sample of 55 participants. The pilot demonstrated that the instrument was technically suitable in terms of face validity and internal consistency (Cronbach’s alpha of most scales > 0.70) for the main survey. In total 450 eligible participants who provided informed consent completed interviews and were included in this study.
Participants were verbally informed about the study, that participation was voluntary, that they had the right to withdraw at any point, and, that data would be handled confidentially. After obtaining informed consent, an anonymous, structured questionnaire was administered to participants as a face-to-face interview. To limit external interference, interviews were conducted either in participants’ homes, in the home of researchers or a location convenient to participants. For those interviewed at worksites or on streets, permission was sought to interview participants separately. Well-trained interviewers and individualized interviews were also able to reduce the effect of the external environment. Each questionnaire took approximately 30–45 minutes to complete. Each participant was given AU$10 to compensate for his time. The study protocol was approved by the Institutional Review Boards at both Queensland University of Technology in Australia and Hanoi Medical University in Vietnam.
The measures for the constructs of the original and modified model are presented in Table 1.
Risky Drug Use Behavior was assessed with five items  asking 1) if participants ever took a drug in their lifetime, 2) if they ever injected a drug in their lifetime, 3) how often did they inject drugs during the past month, 4) how often did they re-use syringes offered from other peers during the past month, and 5) how often did they offer their syringes to other peers during the past month. Items 3, 4 and 5 were then classified into a dichotomous scale with 0 being coded as no or a lower level of the respective practices, and 1 being labeled as a higher level of each practice. These items were summed to form a composite score of the level of risky drug use behavior (α = .82).
SEM , the main procedure of statistical analysis, was conducted with data from 450 male laborers for a principal outcome variable of risky drug use. We adopted the Weighted Least Squares (WLS) estimation given that some of the variables in the model were not normally distributed. Model fit was assessed first with the p-value of WLS Chi square and then with the comparative fit index - CFI [39, 40] and the root-mean-square error of approximation – RMSEA . To be fit, WLS χ2 should be not significant (i.e. P > 0.05). The CFI ranges from 0 to 1, with .90 indicating acceptable fit and .80 indicating marginal fit . The RMSEA ranges from 0 to ∞, with fit values less than .05 indicating close fit and less than .10 indicating fairly acceptable fit . The CFI and RMSEA are sensitive to model misspecification and are minimally affected by sample size . Both the original and modified IMB models were first tested separately, followed with an examination of their fit to which model is better to predict risky drug use.
Sample characteristics and drug use patterns of male laborers
The mean age of male unskilled, unregistered laborers was 39 years. These men had a minimal education level (mean grade completed = 8; in Vietnam the education system classifies 12 grades ranging from 1 to 12 for primary, secondary and high school, and over 12 for higher education). Most were married (84%), migrant (87%), ethnic Kinh (~98%), Buddhist and ancestor worship followers (~66%), and rural workers (60%). The majority (~60%) were farmers in their hometown and the most common occupation during their urban stay was motorbike driver (~65%), followed by manual laborer and construction worker, each contributing more than 10% of the total. The average monthly income was 2.6 million VND (an equivalent of U.S.$130). The response rate was high, representing 95% of the participants.
Characteristics of drug use
Variable (N = 450)
Lifetime drug use (N = 450)
Average age at first use (N = 77, range = 15-50)
26.95 ± 9.69
Lifetime drug injection (77)
Average age at first injection (N = 75, range = 16-51)
29.12 ± 9.79
Injection use during the past month (n = 77)
Frequency of injection (range = 0-6)*
3.4 ± 1.38
None during the past month
Less than monthly
Around once per month
A few times per month
A couple of times per week
Sharing syringes and needles given by other users during the past month (N = 75)
Frequency of sharing syringes and needs (range = 0-5)*
3.01 ± 1.31
About half of the time
Giving syringes and needles to other users to share during the past month (N = 75)
Frequency of sharing syringes and needs (range = 0-5)*
2.83 ± 1.31
About half of the time
Purchasing syringes and needles during the past month (N = 75)
Purchasing syringes and needles (range = 0-4)*
2.15 ± 1.06
Keeping syringes and needles available during the past month (N = 75)
Frequency of keeping syringes and needles (range = 0-4)*
2.15 ± 1.17
Discussing or persuading peers not to share syringes and needles when injecting (N = 75)
Frequency of discussing or persuading peers not to share (range = 0-4)*
1.75 ± 1.17
Descriptives of modified IMB model constructs
Means and standard deviations and correlates among modified IMB model constructs
± SD (Range)
.35 ± .77 (0–10)
5.66 ± 4.83 (0–28.50)
7.20 ± 3.79 (0–20)
6.65 ± 5.16 (0–27)
2.70 ± 1.04 (0–4)
1.5 ± 0.97 (0–3)
26.40 ± 4.58 (10–35)
26.35 ± 5.18 (8–35)
25.85 ± 5.44 (7–35)
10.79 ± 2.63 (3–15)
7.07 ± 1.90 (2–10)
12.Drug Use Level
2.81 ± 1.31 (0–5)
The mediation effect of behavioral skills in the IMB model continued to be examined (data not shown in the interest of space). When we removed two paths from information and motivation to behavior, the path coefficient from information to behavioral skills was still significant (β = .47, P < .05), the path coefficient from motivation to behavioral skills was increased (β = .33, P < .05), and the path coefficient from behavioral skills to behavior significantly increased (|β| = .49, P < .01). When we removed two paths from information and motivation to behavioral skills, path parameters from information and motivation to behavior appeared unchanged. These data suggest that behavioral skills was a complete mediator between information, motivation and behavior.
In this study among male street laborers, most of whom were rural-to-urban migrant, low-skilled and unregistered, over 17% were drug users. Compared with other populations, the proportion of drug users in our sample was much higher. More than 10% of Vietnamese youths aged 15–24 in Quangninh province used drugs , almost 11% of the general population in urban Thailand similarly use , and the rate among several communities in some areas of rural and urban China was 1% . Unfortunately, data on the drug use behavior identified in this present study are not comparable in Vietnam given the lack of previous research examining this issue among rural–urban migrant low-skilled workers. With regards to injecting risk behaviors, our data is quite consistent with studies by Lurie et al.  of drug users in some parts of Africa, by Deren et al. of Puerto Rican drug users in the New York , and Yang, et al. of drug users in southwestern China  demonstrating that needle sharing was not uncommon. As reported by Deren et al. , over one-third of American injectors shared syringes or other paraphernalia associated with HIV and hepatitis C (HCV) transmission (cookers, cotton, water), and 15% used shooting galleries. Similarly, according to data by Yang et al. , close to 60% of the sample of drug users injected drugs, and 35% of those who injected drugs shared used needles when injecting during the past 30 days in China.
The current study also found that male street laborers showed moderate knowledge and understanding of HIV/AIDS and the risk behaviors associated with transmission. They were also moderately motivated and reported fairly high behavioral skills to prevent HIV transmission, but still engaged in risk behaviors related to injecting drugs. The findings of this study seem to support previous data. For instance, heroin users in American methadone maintenance programs , adolescent substance users in the US , and truck drivers in India  had a relatively moderate understanding of HIV theory, displayed a medium level of motivation, including attitudes, norms and intentions, and reported perceived higher behavioral skills for HIV prevention, but practiced a drug use risk behavior at high level.
Comparison of percentage variance across various populations
Outcome variable (model version)
Percentage variance in outcome variable
Male street laborers
Drug use behavior (Modified IMB)
Our current study
Male street laborers
Sexual behavior (Modified IMB)
Indian truck drivers
Sexual behavior (IMB)
Sexual behavior (IMB)
Urban minority high school males
Sexual behavior (IMB)
Urban minority high school females
Sexual behavior (IMB)
Low-income African American females
Sexual behavior (IMB)
Low-income white females
Sexual behavior (IMB)
Netherlands adult homosexual males
Sexual behavior (IMB)
Heterosexual university males and females
Sexual behavior (IMB)
Homosexual adult males
Sexual behavior (IMB)
Given the current results, it is recommended that a sound HIV control program targeting this population not only distribute information and enhance motivators (attitudes, norms, and intentions) for HIV prevention, but also consider interventions that could improve self-efficacy or behavioral skills in order to increase drug use-related preventive behaviors or reduce risky behaviors for HIV. The findings highlight an important point for designing intervention programs for these men. For a high risk behavior as injection drug use, it appears to be essential to focus upon individual and psychological factors, while it may also be helpful to investigate broader environmental and social factors that would contribute to drug use.
This study has some limitations. Its cross-sectional design may have precluded the ordering of causality. Self-report bias was also possible due to the social unacceptability of drug use. Since there were some questions that required respondents’ recall, recall bias may be unavoidable. The construct validity of the variables in the model has been examined based on Pearson’s product moment correlation statistics between pairs of variables and the results of factor analysis for the scales used in the model. As Vietnam has many cities that resemble Hanoi, the results of this study could be helpful to other similar urban settings.
However, these limitations notwithstanding, the study provides some significant insights. As it is the first study to examine the fit of the IMB model with this under-researched population, it contributes to our understanding and literature. Further, most of the model constructs were measured with multiple items which were assessed with adequate reliability. Finally, as this is a preliminary investigation, this leads us to a number of interesting implications for further research and intervention in this area. Interventions designed for this population should seek to address informational and motivational impediments to a change in risky drug use behavior as well as improve behavioral skills which help reduce risky drug use behavior. Future research that uses intervention designs with longitudinal follow-up will be crucial for determining causal ordering of the model constructs. There is also a need for further examination of the modified model of IMB in relation to the original version in other populations in order to support interpretations of model fit and consistency. The modified model may include broader environmental and social factors which contribute to risky drug use.
Overall, this research is a first step toward further research into high risky drug use behavior and factors that may fuel the HIV epidemic among such men. The research is helpful in building an increased understanding of the risks for HIV infection and transmission among male street laborers enabling policy makers and practitioners to deal with this uncertain, disturbing, and increasing epidemic. An AIDS prevention program for these men should not only distribute information and enhance motivations for HIV prevention, but consider interventions that could improve self-efficacy for preventing HIV infection. Future public health research and action may also consider broader factors such as structural social capital and social policy to alter the conditions that drive risky drug use among these men. As Hanoi has much in common with many other rapidly urbanized cities in Vietnam, this research provides evidence, policy and practical implications that can be useful to urban settings within the country.
HVN, a Master of Health and International Development, a PhD in Public Health, is a lecturer and a researcher of the Department of Health Management and Organization, Institute for Preventive Medicine and Public Health, Hanoi Medical University (HMU), Vietnam.
DPM, a PhD, a Professor of Social Epidemiology, is a senior lecturer of the School of Public Health and Social Work at Queensland University of Technology in Brisbane, Queensland, Australia, and a director of Vietnam-Queensland University of Technology Public Health Cooperation Program, Australia.
DJ, a PhD, an Associate Professor, is a researcher at Brisbane Sexual Health and HIV Service, MetroNorth Hospital and Health Service, in Brisbane, Queensland, Australia.
Information-Motivation-Behavioral Skills model
Structural equation modeling
Vietnam Dong (the Vietnamese currency)
Weighted Least Squares.
This study was supported by grants awarded from the Institute of Health and Biomedical Innovation from the Queensland University of Technology, and the Australian Government’s Overseas Aid Program (AusAID). The author also thanks the field teams for their tireless efforts to assist this study. The author gratefully acknowledges the participation of all male labourers in the survey interviews in Hanoi city, Vietnam.
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