SEX DIFFERENCES IN INJECTING PRACTICES AND HEPATITIS C: A SYSTEMATIC REVIEW OF THE LITERATURE

Introduction

The hepatitis C virus (HCV) was first identified in 1989 in the United States(1). Before its discovery, the disease was referred to as non-A, non-B hepatitis. Hepatitis C is the leading cause of known liver disease in Canada. It is the most common cause of cirrhosis and a frequent cause of hepatocellular carcinoma(2). In North America, hepatitis C is the most common reason for liver transplantation.

The World Health Organization estimates that about 3% of the world's population, or 170 million people, may be infected with HCV(2). In Canada, the number of people with antibody to HCV is estimated to range between 210 000 and 275 000, of whom only about 30% are aware of their infection(3). Data from Health Canada's Enhanced Hepatitis Strain Surveillance System (previously known as Enhanced Surveillance for Acute Hepatitis B and Hepatitis C) for the period 1999 through 2002 inclusive show average incidence rates of acute infection with HCV (per 100 000 person years) of 2.78 among males and 2.22 among females(4). When the data are examined for the most likely mode of self-reported transmission, injection drug use accounted for 57.4% of new HCV infections for that period. With respect to the sex of cases, the data show that, among females, injection drug use accounted for 58.2% of new cases, a slightly higher proportion than the 57.0% observed among males(4).

There are approximately 75 000 to 125 000 injection drug users (IDUs) in Canada, one-third of whom are women(1). It has been suggested that a large proportion of the IDU population is already chronically infected with HCV, creating a large reservoir of infection that contributes to the ongoing high rates of transmission(5). In the absence of a vaccine against hepatitis C, behavioural interventions are the only effective means available to prevent and reduce the spread of the disease. For this reason, interventions need to be further developed to target the behavioural, attitudinal, and social factors that put IDUs at increased risk of infection. In addition, there is a requirement for greater emphasis and investment in the evaluation of interventions to measure outcomes, identification of best practices, and generation of new knowledge.

Although it is understood that a variety of factors affect an individual's initiation and ongoing involvement in injection drug use, this particular review focuses on the influence of gender. Specifically, it examines the current available literature to assess the influence of gender on drug users' injection initiation, sharing behaviour, and cleaning/disinfecting behaviour.

Methods

A number of electronic databases were searched from 1992 to 2003, including MEDLINE, WebSPIRS, BLACKWELL-SYNERGY, GATEWAY and SCIENCEDIRECT. Terms and keywords, used alone or in combination to identify relevant abstracts in each database, included hepatitis C, injection drug use, IDU, gender, indirect sharing, direct sharing, disinfecting, cleaning, power, dynamics, sexual relationship, heroin, cocaine, injecting practices, syringe shortage, age, and risk. All searches were limited to articles published in English. All relevant abstracts were retrieved in full text. Appropriate articles included in the bibliographic references of the full text articles were also retrieved.

Results

The total number of articles retrieved was 95. Of these, 79 were research studies, two were critical responses to studies, 10 were reviews, three were research letters, and one was a chapter from a book. Eleven were Canadian, 51 were American (US), 22 were European, and the remaining articles were either Australian or South American. Only six of the 95 articles were published before 1994; the remaining 89 were published between 1995 and 2003.

Injection initiation

A drug user's first injection is typically unplanned and usually occurs within the person's peer group or social network. A cohort study of 229 participants showed that only 7% of females and 12% of males reported having injected alone on the first occasion of injection, and only one-third of the entire sample had planned their first injection(6).

There are differences between males and females with respect to who helps them initiate injection, in what way they are initiated, and their reasons for beginning injection drug use. The majority of research points to male sex partners as the primary initiators for females(7-10), although one study identified same-sex initiators for both males and females(6). Unfortunately, this study failed to specify whether these same-sex initiators were also sexual partners. Diaz et al., however, found that 9% of women in their cohort who identified themselves as being either lesbian or bisexual reported being injected by their sex partner at their first injection as compared with 26% for heterosexual women(7). This study also found that females were significantly more likely than males to report receiving the drug as a gift, having an initiator who was >= 5 years older than themselves and having sex with the initiator after injecting(7).

At the time of initiation, males are far more likely to self-inject under the guidance of a helper, whereas females more often report being directly injected by a helper(6). Males report that they begin injecting because they can no longer get a satisfactory high from snorting or smoking drugs, whereas females report that they begin injecting because they are curious(6). Despite these differences, males and females are of a similar age (range 16.4 to 19.2 years) when initiated into intravenous drug use(11-15).

Sharing behaviours

Direct versus indirect sharing: Multi-person use of injection equipment is described as both direct sharing and indirect sharing. Direct sharing is the receiving and passing on of syringes and needles between IDUs, and indirect sharing is the sharing of other injection equipment like cookers, cottons (filters), and water for rinsing/mixing(16). This equipment is used to prepare the drug for injection and is most often referred to as "paraphernalia"(11,15). Both types of sharing can transfer HCV, though the risk is greater with direct sharing(14).

Research has shown that the sharing of syringes and other injection equipment continues despite access to sterile equipment. These findings suggest that sharing persists for other reasons. Ethnographic data point to the social context and the "culture" of injecting drugs(17). Specifically, the data suggest that injecting risk is rooted in injecting networks and sexual relationships(17). IDUs commonly form social networks and partnerships to facilitate the acquisition of drugs (by pooling their resources) and for companionship and safety. Implicit to these networks is an obligation of reciprocity and trust among members, which may also increase the risks associated with injecting(17).

When sex differences in sharing behaviour are considered, the literature shows that males tend to share with a larger network of people, including sexual partners, friends and relatives(10,13,17-19). Females' networks are typically smaller and are characterized by greater overlap with their sexual partners. In terms of the regularity of sharing, females report sharing more frequently than males(8,10,11,18-21). Differences have also been reported with respect to the type of sharing that females and males engage in. Specifically, females are more likely to report sharing their needles and syringes, suggesting that they participate more frequently in direct sharing than males(8-11,14,18,19). While the data clearly indicate that females participate in direct sharing more frequently than males, evidence concerning which sex exhibits more indirect sharing is conflicting and therefore inconclusive. It is possible that there are no sex differences in indirect sharing behaviour.

Self-reported reasons for sharing: According to the literature, the most common reason for sharing injection equipment, reported by both male and female IDUs, is the unavailability of clean needles/syringes because the demand exceeds the supply(11,17,22-28). Other reported reasons for needle/syringe unavailability include financial and legal constraints(24,27). Accidental sharing and the immediacy of desire for drugs are also frequently reported reasons for sharing(17).

Type of drug: The type of drug injected also seems to play a role in sharing behaviour. Using heroin as opposed to cocaine appears to be associated with a higher likelihood of sharing equipment(28). This may be because heroin users waste little time between acquiring the drug and injecting it to alleviate their withdrawal symptoms, and are thus more likely to divide the drug during preparation. Although dividing the liquid drug after preparation takes less time than dividing the powdered form before preparation, it involves the practice of front and backloading* as well as the sharing of other injection equipment(24). Either method increases the risk of infection through potential exposure to the blood of an infected IDU. Cocaine is also sometimes divided during preparation, but often cocaine users divide the powdered form and then prepare it, reducing the amount of equipment shared(24). Unfortunately, both male and female IDUs often identify heroin as their drug of choice and/or their most commonly injected drug(6,18,28-35).

Although males and females report some common reasons for sharing, there are a few important differences. Females report that sharing is something that is engaged in with regular sex partners when love, trust, and intimacy are present or desired in the relationship(17,19). In contrast, males primarily report practical reasons for sharing, such as an immediate desire for a "hit" and/or because of an unavailability of clean syringes, needles, and injection equipment(17). Males are also more likely than females to report that they share because they believe it is not dangerous(19).

Cleaning/disinfecting behaviour

In the absence of new injection equipment, cleaning and disinfecting previously used injection equipment becomes an important component in reducing the risk of transmitting HCV and other blood-borne infections(27,36). Many IDUs report that the cleaning of injection equipment is burdensome(37), whereas others may do it willingly. Overall, males are more likely to clean and disinfect their needles, syringes, and injection paraphernalia(8,18). However, there is some indication that cleaning may be dependent upon context. For example, the literature suggests that when injecting with friends males and females engage in equal levels of cleaning behaviour, but that when sharing with sexual partners females are less likely to clean their equipment(8). Further, it has been found that injecting at a friend's house is associated with cleaning shared equipment(38) and that males are more likely than females to inject at a friend's home(10). Also, IDUs who clean their needles after sharing them typically have larger drug networks than those who do not(38).

Discussion

Sex differences

It is apparent from the current review that males and females differ in their injection drug use behaviour. Overall, females seem to be more emotionally oriented when it comes to adopting risky injection practices, whereas males appear to be more practical in their risk taking. Each sex experiences its drug use in different contexts and manners. There appear to be issues of male power within heterosexual IDU sexual relationships that are interacting and contributing to increased risk for females. Females more often inject within an intimate relationship. These relationships provide certain benefits, including companionship and sex, stability and security, and facilitated access to drugs. However, the benefits come at a significant cost - the loss of control and influence over the injection stages and process(18).

Issues of power imbalance appear to first emerge with injection initiation. Males gain control of the initiation by directly injecting females after first injecting themselves(38). Frequently, females fail to learn how to inject themselves and become injection dependent on other IDUs, often requiring help to inject throughout their injection careers(6,18,23,39-42). This may lead females to feel that the injection process is out of their control and that they do not possess the power to insist that injection equipment not be shared or that equipment be cleaned between users. Further, as noted earlier, females are more likely than males to share equipment with their sexual partners. They believe that sharing with their sexual partner will confirm or create the presence of love, trust, and intimacy in their relationship(17,19). Although their desire is to maintain or create an emotional connection with their partner, females who allow their male sexual partners to inject them with used equipment are ultimately confirming their subordination rather than gaining an emotional link(17).

Similarly, problems of gender-based power imbalance are observed in sexual relationships with respect to the adoption of risky sexual behaviours. Often, if the male decides not to use a condom the female accedes, possibly because she feels she does not have the power to object(43) or because she wants to confirm and/or create trust and intimacy in the relationship. There also appears to be an interaction between adopting risky sexual behaviours and engaging in risky injection behaviours. More often than not, once an IDU sexual couple has adopted unsafe sexual practices the partners are more likely to share injection equipment because this behaviour is perceived to be of a similar magnitude of risk or because it is already too late(12,13). Paradoxically, sharing injection equipment is far riskier than engaging in unsafe sex in terms of contracting HCV(12).

Limitations of the research

Approximately 63% of the articles in this literature review studied a North American population; only 11 of the 95 (11.6%) used a Canadian sample. Therefore, it is unknown whether the findings can be generalized to the Canadian population.

Thirteen out of the 95 articles included in this review reported on HIV rather than hepatitis C. It is possible that some of the generalizations made from these studies may not apply directly to HCV. However, given that injection drug use is a common mode of transmission for both infections and that it is the behaviours associated with injection drug use that are of interest, such generalizations should be appropriate.

Problems were encountered when searching for trends among papers because of poor study designs and sampling methods. Most of the studies examined cohorts of IDUs and, thus, could not sample randomly. A lack of random sampling makes it impossible to conclude whether the trends observed among studies are valid and also makes it difficult to generalize to the entire IDU population.

Conclusion

From the present review, it can be concluded that male and female injection drug users differ with respect to injection initiation, equipment sharing, and equipment cleaning. Although there are some similarities between the sexes, the differences require more attention because they have a greater impact on the adoption of risk behaviours and the transmission of hepatitis C. It is especially important to take note of the gender-based power dynamics within heterosexual IDU sexual relationships because this power imbalance directly affects the adoption of risk reduction behaviour.

Since male and female IDUs often constitute one another's drug networks, their relationships become crucial to the acceptance of risk behaviour. Often, a male drug user's decision to engage in risky behaviour can be a female drug user's constraint or vice versa(44).

Current harm reduction and prevention strategies have fallen short of reducing the incidence of new infections(42,45), including HCV. Understanding the social circumstances of injecting and, in particular, differences between male and female drug injectors' practices and their interactions is crucial to developing gender-sensitive education and prevention programs in order to reduce or prevent the transmission of hepatitis C within the injection drug using population.

Note

* Frontloading is transferring the drug from one syringe directly into another syringe after removing the needle, and backloading is doing the same after removing the plunger.

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Source: R Roman-Crossland, MA, University of Guelph; L Forrester, MSc, Canadian Viral Hepatitis Network; G Zaniewski, MHSc, Blood Safety Surveillance and Health Care Acquired Infections Division, Centre for Infectious Disease Prevention and Control, Health Canada.


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