International Epidemiological Association 2001
International Journal of Epidemiology 2001;30:1449–1454 Sex trade involvement and rates of human immunodeficiency virus positivity among young gay and bisexual men
Amy E Weber,a Kevin JP Craib,a Keith Chan,a Steve Martindale,a Mary Lou Miller,aMartin T Schechtera,b and Robert S Hogga,b
Background Susceptibility to human immunodeficiency virus (HIV) infection is of particular
concern for marginalized populations. The objective of this study was to deter-mine risk factors associated with sex trade work among young gay and bisexualmen. Further, we aimed to compare HIV prevalence and incidence among meninvolved and not involved in sex trade work.
The study is based upon data obtained from a prospective cohort study of younggay and bisexual men. Participants had completed a baseline questionnaire whichelicited information on demographic information, sexual behaviours, and sub-stance use. Sex trade involvement was defined as the exchange of money, drugs,goods, clothing, shelter or protection for sex within the one year prior to enrol-ment. Contingency table and multivariate logistic regression analyses were usedto identify risk factors associated with involvement in the sex trade.
Of the 761 eligible participants, 126 (16%) reported involvement in sex tradework. Multivariate logistic regression analysis revealed regular alcohol use (OddsRatio [OR] = 3.6, 95% CI : 1.8–7.2), aboriginal ethnicity (OR = 3.7, 95% CI : 1.6–8.7),unemployment (OR = 3.9, 95% CI : 2.1–7.3), history of residence in a psychiatricward (OR = 4.2, 95% CI : 1.8–9.8), bisexual activity (OR = 7.0, 95% CI : 3.5–14.1)and the use of crack (OR = 7.4, 95% CI : 3.0–18.7) to be independently associatedwith sex trade work. Sex trade workers had a significantly higher HIV prevalenceat baseline compared with non-sex trade workers (7.3% versus 1.1%, P Ͻ 0.001). As well, HIV incidence was found to be significantly higher for sex trade workerscompared with non-sex trade workers (4.7% versus 0.9%, P = 0.011).
Our study reveals that for male sex trade workers in this setting increased vul-nerability to HIV infection is related to unfavourable living conditions, substanceuse and sexual risk behaviour.
Homosexual men, sex trade worker, risk factors, sexual behaviour, housing
In Canada, gay and bisexual men have been seriously affected
overall proportion of men infected with HIV, gay and bisexual
by the human immunodeficiency virus/acquired immuno-
men continue to be greatly affected by the HIV/AIDS epidemic.
deficiency symdrome (HIV/AIDS) epidemic. In 1985, 83% of
In the US, gay and bisexual men accounted for 50% of AIDS
all reported AIDS cases among adult males occurred in this
cases and 43% of non-AIDS cases in 1996.2
population. By 1995, the percentage of reported cases in this
Sexual transmission among gay and bisexual men continues
category had decreased to 74%.1 Despite a reduction in the
to be a major source of new HIV infections in Canada. As is truefor other populations, subgroups of men who have sex withmen may be at increased risk for HIV infection. Also, they may
a British Columbia Centre for Excellence in HIV/AIDS, St Paul’s Hospital,
be less likely to be reached by prevention messages aimed at
bDepartments of Health Care and Epidemiology, University of British
the broader gay and bisexual community.3 These vulnerable
subgroups include men who inject drugs, trade sex for money
Correspondence: Robert Hogg, Program Director, Division of Epidemiology
or drugs and those men who do not self-identify as gay or
and Population Health, BC Centre for Excellence in HIV/AIDS, 608–1081Burrard St, Vancouver, BC V6Z 1Y6, Canada. E-mail: [email protected]
It is important to identify whether men who engage in the
variables including the frequency of receptive and insertive anal
sex trade are a demographically and behaviourally distinct sub-
intercourse with regular and casual partners; and the frequency
group of gay and bisexual men in order to develop better and
of condom use during receptive and insertive anal intercourse.
more focused intervention programmes. This analysis aimed to
The use of alcohol and other drugs was also assessed. For the
determine risk factors associated with involvement in sex work
purpose of this analysis unstable housing was defined as living
among young gay and bisexual men in order to have a better
in a hotel, boarding house, group home, in the street or having
profile of their lives. Further, as men involved in sex work have
been identified as being at increased risk of HIV infection, we
The HIV prevalence and incidence calculations were also
compared HIV prevalence and incidence for men involved and
compared for the two groups. The HIV incidence was calculated
as the number of new infections divided by the total person-time under observation. Person-time was calculated as theinterval between enrolment and the most recent follow-up visit
for subjects who did not seroconvert through January 1999. For
The Vanguard Project is an ongoing prospective study of over
subjects who became HIV positive, person-time was calculated
900 gay and bisexual men in the Greater Vancouver region.
as the interval between enrolment and the first visit at which an
Men were eligible to participate if they were aged 18–30 years,
HIV positive test result was detected. The 95% CI for the incid-
lived in the Greater Vancouver region, had not previously tested
ence estimates were calculated based on the Poisson distribution.
HIV-positive, and self-identified as gay or bisexual or reported
Categorical variables were compared between groups using
having sex with other men. Potential participants were re-
Pearson’s χ2 test. Contingency tables that contained one or more
cruited through community outreach at gay community events,
expected counts of less than five were analysed by the Fisher’s
community health clinics or local physicians, and through the
exact test. Comparisons of continuous variables were carried
out using Wilcoxon’s rank-sum test. All variables that were foundto be significant at P р 0.05 in the univariate analyses were
entered into a stepwise multivariate logistic regression model
Since May 1995, participants completed a detailed self-
that was used to identify independent risk factors associated
administered questionnaire and provided a blood sample for HIV
with involvement in the sex trade. Participants with missing
antibody testing at baseline and annually thereafter. Completed
data for variables entered into the multivariate model were
baseline questionnaires provide demographic data as well as
excluded from the analysis. All reported P-values are two-sided.
information regarding sexual behaviours. Included are aspectsof insertive and receptive anal and oral sex with regular partners
(men with whom you have sex at least once per month), casualpartners (men with whom you have sex less than once per
Of the 761 eligible participants, 126 (16%) reported that they
month) and paid partners (sex exchanged for money, drugs,
were involved in sex work. Comparison of sex trade workers
goods, clothing, shelter or protection). Participants are also asked
versus non-sex trade workers revealed significant differences
whether they have ever been forced to have sex (any type of
with respect to socio-demographic characteristics (Table 1). Sex
sexual activity that you were forced or coerced into against your
trade workers were younger (median: 23 years versus 26 years,
will), and the age range when this first occurred. Participants
P Ͻ 0.001), more likely to be Aboriginal (29% versus 6%,
completed a seven-item abbreviated version of the Centres for
P = 0.001), and to have less than a high school education
Epidemiologic Studies of Depression (CES-D) scale. Participants
(40% versus 12%, P Ͻ 0.001). Sex trade workers were more
were classified as being clinically depressed if their score on the
likely to report living in unstable housing (45% versus 4%,
abbreviated CES-D scale was greater than the median value for
P Ͻ 0.001), to have an annual income of less than $10 000
the cohort. Additionally, participants answered questions about
(58% versus 26%, P Ͻ 0.001), and to have ever been in a psy-
their use of legal and illegal recreational drugs including
chiatric ward (32% versus 6%, P Ͻ 0.001). Further, sex trade
alcohol, tobacco, nitrite inhalants (poppers), marijuana, cocaine
workers were found to have a high depression score (82%
and heroin. Baseline questionnaires were used to assess these
versus 50%, P Ͻ 0.001) and to have ever been in jail (54%
versus 6%, P Ͻ 0.001) compared with non-sex trade workers.
Table 2 outlines differences in reported sexual behaviours of
sex trade workers and non-sex trade workers. Sex trade workers
The analysis presented here is limited to those individuals who
reported a younger median age at first consensual sex with both
had completed a baseline questionnaire and HIV test between
men (15 years versus 18 years, P Ͻ 0.001) and women (14 years
May 1995 and January 1999. As noted above, sex trade in-
versus 17 years, P Ͻ 0.001). Sex trade workers were found to
volvement was defined as the exchange of money, drugs, goods,
be significantly more likely to report bisexual activity (48%
clothing, shelter or protection for sex. It is important to note
versus 8%, P Ͻ 0.001), and to having ever experienced non-
that for the purposes of this analysis any man who reported sex
consensual sex (49% versus 32%, P Ͻ 0.001) compared with
trade involvement in the year prior to baseline were included.
those men not involved in the sex trade.
In order to assess risk factors associated with involvement in the
With respect to sexual encounters with regular and casual
sex trade, we conducted cross-sectional comparative analyses.
partners, a lower proportion of sex trade workers reported un-
Variables of interest in these comparative analyses included:
protected insertive (50% versus 75%, P Ͻ 0.001) and receptive
socio-demographic characteristics such as age, ethnicity,
(53% versus 75%, P Ͻ 0.001) oral sex with regular partners.
income, housing status and education; sexual behaviour
There were no statistical differences in the proportion of people
DETERMINANTS OF INVOLVEMENT IN THE SEX TRADE
Table 1 Reported socio-demographic characteristics of male sex trade workers and non-sex trade workers Sex trade workers Non sex trade workers P-value Ethnicity Less than high school education Unstable housing Income Ͻ$10 000/year Ever in psychiatric ward High depression score (CES-D Ͼ12) Ever in jail
NB: Column totals may not equal total number of subjects due to missing values. Table 2 Reported sexual experiences of male sex workers and non-sex trade workers Sex trade workers Non sex trade workers P-value Age at first sexual experience with: Bisexual activity in previous year Non-consensual sex (ever)
NB: Column totals may not equal total number of subjects due to missing values.
reporting unprotected anal intercourse with regular partners or
Substance use was also found to be higher among the sex
unprotected oral sex with casual partners. However, higher levels
trade workers compared with non-sex trade workers (Table 4).
of unprotected insertive (28% versus 15%, P = 0.002) and
Compared with non-sex trade workers, sex trade workers
receptive (20% versus 13%, P = 0.042) anal sex were reported
were more likely to consume more than 10 drinks per week
with casual partners for sex trade workers compared with non-
(39% versus 13%). As well, a higher proportion of sex trade
workers reported the use of poppers (43% versus 28%), cocaine
Table 3 Reported unprotected sexual behaviour with regular and casual partners in the year prior to baseline for male sex trade workers and non-sex trade workers Sex trade workers Non sex trade workers P-value Regular partners Casual partners
NB: Column totals may not equal total number of subjects due to missing values. Table 4 Comparison of substance use in the year prior to baseline for male sex trade workers and non-sex trade workers Sex trade workers Non sex trade workers P-value Greater than 10 drinks/week Injected drugs
NB: Column totals may not equal total number of subjects due to missing values.
(63% versus 25%), crack (38% versus 4%), and heroin (30%
1.1%, P Ͻ 0.001). As well, the HIV incidence rate was found to
versus 3%) compared with non-sex trade workers (all P Ͻ 0.001).
be significantly higher for sex trade workers 4.7/100 person years
Sex trade workers were also more likely to report having
(pyrs) (95% CI : 0.1–9.4/100 pyrs) compared with non-sex
injected drugs in the year prior to baseline compared to non-sex
trade workers 0.9/100 person years (95% CI : 0.3–1.5/100 pyrs)
trade workers (32% versus 4%, P Ͻ 0.001).
The results of the logistic regression analysis of independent
factors associated with involvement in the sex trade are sum-
marized in Table 5. The regular use of alcohol characterized by having more than 10 drinks per week was associated with a
Comparison of male sex trade workers and other young gay and
3.6-fold increase in the likelihood of being involved in sex trade
bisexual men revealed many important differences with respect
work. Further independent risk factors for involvement in sex
to risk factors associated with sex work. Sex trade workers were
trade work were aboriginal ethnicity (Odds Ratio [OR] = 3.7),
more likely to be marginalized as characterized by their younger
being unemployed (OR = 3.9), having ever been in a psychiatric
age, low levels of education, unstable housing and low annual
ward (OR = 4.2), engaging in sexual relations with both men
incomes. Aboriginal status was found to be independently asso-
and women (OR = 7.0) and using crack (OR = 7.4).
ciated with sex work. Although the proportion of aboriginal
Sex trade workers had a significantly higher HIV prevalence
men in our study who were involved in prostitution (20%) was
at baseline compared with non-sex trade workers (7.3% versus
much lower than that recently reported for youth in Canada,4
DETERMINANTS OF INVOLVEMENT IN THE SEX TRADE
Table 5 Multivariate logistic regression model: Risk factors associated with involvement in the sex trade (n = 521) Unadjusted odds ratio Adjusted odds ratio Use of alcohol Aboriginal ethnicity Unemployed Psychiatric ward Bisexual activity Use of crack
Aboriginal men are over-represented in the sex trade worker
Prostitution is an economic necessity for many drug users,
population. To date there is little research of male sex trade
both male and female.20 Our results indicate that a significantly
workers from different ethnic backgrounds. However, Aboriginal
higher proportion of sex trade workers used both non-injection
men have been found to make up a significant proportion of
and injection drugs compared with the rest of the cohort. The
men involved in prostitution, street youth and injection drug
proportion of sex trade workers reporting the use of poppers,
users.5,6 Further evidence of the marginalized status of these
cocaine, crack and heroin was significantly higher than other
men include the higher proportion of sex trade workers report-
gay and bisexual men in this study. People who use injection
ing having ever been in a psychiatric ward, having a high depres-
drugs are at particular risk for HIV infection because they may
sion score and having ever been incarcerated. Unemployment
be exposed to the virus through both unprotected sex and the
and a history of residence in a psychiatric ward were found to
sharing of injection equipment.21,22 de Graff et al.8 reported
be independently associated with sex work. These differences
that heavily addicted drug users were less discriminating in
are consistent with other studies that have shown sex trade
their choice of clients, and lowered their barriers more easily
workers to be living in impoverished conditions confounded by
when it came to performing sexual acts without using condoms.
mental illness and substance use.7–9
Substance use characterized by the consumption of more than
Sex trade workers may be at increased risk of infection 10 drinks per week and the use of crack was found to be inde-
with HIV due in part to their sexual and drug using behaviours.
pendently associated with sex work. The relationship between
Men involved in sex work were on average younger at first
substance use and sex work is complex. Studies have shown that
consensual sex with both males and females compared with
in some cases substance use precedes entry into prostitution
non-sex trade workers. This finding corroborates earlier work
while in others, sex work is used as a means to earn money
by Earls and David10 that indicated that male prostitutes were
to buy drugs.10,23 Regardless of the temporal relationship, it is
significantly younger than the comparison group in terms of the
important to recognise the relationship and acknowledge the
age at first sexual interaction. Younger age at first coitus has
importance of drug treatment for these men. The use of crack is
been linked to risky sexual behaviour including multiple sexual
of further concern because it has been linked with such sexual
partners.11 Sex trade workers in our study were found to have
behaviours as inconsistent condom use and multiple partners
lower rates of unprotected oral sex with regular male partners
that may increase an individual’s risk of infection with
and higher rates of unprotected anal sex with casual male
partners. The latter finding may contribute to the significantly
The prevalence of HIV for male sex trade workers was signifi-
higher HIV prevalence and incidence rates found for sex trade
cantly higher than for other gay and bisexual men in this study.
workers compared with non-sex trade workers. Reporting of a
However, the prevalence is fourfold lower than the rates reported
history of non-consensual sex was higher for sex trade workers
for male prostitutes in Atlanta, USA.28 The independent risk
compared with the rest of the cohort. These data are consistent
factors for sex trade involvement highlighted in this study may
with other studies showing a relationship between non-consensual
contribute to increased risk of HIV infection. Minority status
sex and involvement in the sex trade.10,12–14 Bisexual activity
and marginalization have been linked with increased HIV pre-
was found to be independently associated with sex trade involve-
valence.6,7,29 Involvement in bisexual activity may increase the
ment. Previous research has suggested that men may self-identify
risk of HIV infection due to the relationship between bisexual
as heterosexual and report female sex partners but engage in
activity and involvement in sex work.15 Substance use has been
sexual activity with other men for profit.15–17 A number of studies
linked with risk of HIV infection because the consumption of
have suggested that male sex trade workers are a potential link
alcohol and drugs may interfere with judgement and decision-
between homosexual and heterosexual transmission of HIV.18,19
making thereby potentially increasing unsafe sexual behaviour.30
The danger of HIV infection spreading through homosexual
As is the case with many population-based studies, this is a
prostitution is very real, but the actual risk depends to a great
sample of convenience. Prostitution is a highly heterogeneous
extent on which sexual practices and precautionary measures
activity, with sex being sold in saunas, bars, clubs, public toilets,
through escort agencies and contact advertisements, as well as on
the street.31 The sex trade workers involved in our study self-
10 Earls CM, David H. A psychosocial study of male prostitution. Arch Sex
identified and were not asked the location from which they sell
sex, and so it is difficult to say whether we have adequately
11 Greenberg J, Magder L, Aral S. Age at first coitus: A marker for risky
represented the male sex worker population in Vancouver. As
sexual behavior in women. Sex Transm Dis 1992;19:331–34.
well, the definition of sex work used in this study is very broad
12 Strathdee SA, Hogg RS, Martindale SL et al. Determinants of sexual
and this must be taken into account when interpreting the
risk-taking among young HIV-negative gay and bisexual men. J Acquir
results. The issue of temporality must be taken into considera-
Immune Defic Syndr Hum Retrovir 1998;19:61–66.
tion in the interpretation of the multivariate analysis. It is
Bartholow BN, Doll LS, Joy D et al. Emotional behavioural and HIV
important to note that we have not examined causation in the
risks associated with sexual abuse among adult homosexual and bisexual men. Child Abuse Neglect 1994;18:747–61.
analysis. Therefore it is not possible for us to determine whether
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