|
Oral presentation
in November 1998, in Ottawa, at the 7th Annual Meeting of HIV/AIDS
Surveillance & Epidemiology.
Comparison of Sexual Behaviors, Condom Use, and Substance
Use between Two Independent Cohorts of Gay and Bisexual Men in
Vancouver
Presented by Dr. Robert Hogg, on
behalf of...
Peter G.A. Cornelisse, Msc; Kevin J.P.
Craib, MMath; Steve L. Martindale; Michael V.
O'Shaughnessy, PhD; Martin T. Schechter, OBC, MD, FRCP, PhD; Julio S.G. Montaner, MD; Robert S. Hogg, PhD; for the Vanguard Project;
UBC and the BC Centre for Excellence in HIV/AIDS.
OBJECTIVE
To compare demographic characteristics, sexual practices and
substance use between seronegative gay and bisexual men who have
participated in two independent prospective studies: the Vanguard
Project (VP) and the Vancouver Lymphadenopathy AIDS Study (VLAS).
METHODS
The Vanguard Project (VP):
An ongoing prospective study of over 600 gay and bisexual
men aged 18 to 30, living in the Greater Vancouver region who
were recruited through outreach, clinics, and physicians' offices.
Men were eligible to participate in this longitudinal study
if they had not previously tested HIV-1 positive, and if they
self-identified as men who have sex with men (MSM). Since May
1995, VP participants have completed self-administered questionnaires
and undergone HIV-1 testing on an annual basis.
Vancouver Lymphadenopathy-AIDS Study (VLAS):
From November 1982 to December 1984, over 700 gay and
bisexual men aged 18 to 75 were recruited through six general
practices in central Vancouver. Follow-up visits occurred approximately
every six months until September 1986 after which subjects completed
visits on an annual basis.
During each visit subjects completed a self-administered questionnaire
which elicited information regarding demographic characteristics,
sexual practices, and other variables.
In addition, a physical examination was performed and blood
samples were drawn for immunologic and HIV antibody testing.
To assess differences in behavioural and other risk factors
for HIV-1 transmission between these cohorts, we conducted two
cross-sectional comparative analyses.
First analysis:
We compared 235 VP participants who were HIV-1 negative
when they completed their enrolment questionnaire during the period
May 1995 to April 1996, and 263 VLAS participants who were
HIV-1 negative when they completed a follow-up visit during the
period January to December 1985.
For VLAS participants, we chose this follow-up visit for comparison
because this was the earliest study visit from which information
about condom use was available.
Second analysis:
We compared 235 VP participants with those VLAS participants
who were between the ages of 18 to 30 at the time of the follow-up
visit (n=82).
SEXUAL BEHAVIOUR
For sexual behaviour variables, a distinction was made between
sexual encounters with regular and casual partners.
- Regular partners: Defined as those partners
with whom the frequency of sexual encounters was at least once
per month.
- Casual partners: Defined as those partners
with whom the frequency of sexual encounters was less than once
per month.
STATISTICAL METHODS
Categorical variables were compared between cohorts using Pearson's
chi-square test. Contingency tables which contained one or more
expected counts of less than five were analyzed by Fisher's exact
test.
Comparison of quantitative variables between cohorts were carried
out using Wilcoxon's rank-sum test.
All p-values were two-sided.
SEROCONVERSIONS
Vanguard (1995 - 1997):
- 7 seroconversions out of 235 subjects (3.0%).
VLAS (1985 - 1991):
- 31 seroconversions out of 263 subjects (11.8%).
CONCLUSIONS
Although younger gay and bisexual men currently report higher
numbers of sexual partners and sexual activities than in the mid-1980s,
the frequency of condom use has significantly increased during
high-risk sexual behaviours.
Table 1:
Comparison of
DEMOGRAPHIC CHARACTERISTICS
between participants in theVanguard Project and the Vancouver Lymphadenopathy-AIDS Study
(VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Age (at baseline): |
| Median: |
26 years |
34 years |
<0.001* |
| Range: |
18-30 yrs |
19-61 yrs |
| Ethnicity: |
| Caucasian: |
176 (75%) |
255 (97%) |
<0.001 |
| Other: |
59 (25%) |
8 (3%) |
| Income: |
|
< 10,000: |
48 (21%) |
52 (20%) |
0.688 |
|
> 10,000: |
178 (79%) |
211 (80%) |
| Education (attended university): |
|
No: |
148 (65%) |
142 (54%) |
0.014 |
|
Yes: |
80 (35%) |
121 (46%) |
* Wilcoxon rank-sum test.
Table 2:
Comparison of self-reported
NUMBERS of SEXUAL PARTNERS
between participants in the Vanguard Project and the Vancouver Lymphadenopathy-AIDS Study
(VLAS)
|
Vanguard
(n=235) |
VLAS
(n=263) |
p-value |
| Number of sexual partners during the past
year: |
|
Mean:
Standard deviation:
Median:
Range: |
15.2
32.5
5
0-400 |
12.2
24.9
4
0-196 |
0.026* |
| Number of REGULAR sexual partners during the
past year: |
|
Mean:
Standard deviation:
Median:
Range: |
1.7
2.8
1
0-30 |
0.6
0.6
1
0-3 |
<0.001* |
| Number of CASUAL sexual partners during the
past year: |
|
Mean:
Standard deviation:
Median:
Range: |
12.5
21.2
4
0-120 |
11.5
24.9
4
0-194 |
0.067* |
* Wilcoxon rank-sum test.
Table 3:
Comparison of self-reported frequency of
ANAL INTEROURSE and CONDOM USE
with REGULAR partners among participants in the Vanguard Project
and the Vancouver Lymphadenopathy-AIDS Study (VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Receptive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
13 (8%)
63 (39%)
27 (17%)
59 (36%) |
59 (40%)
52 (35%)
28 (19%)
8 (5%) |
<0.001 |
|
162 (100%) |
147 (100%) |
| Frequency of condom use during receptive anal
intercourse:* |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
23 (15%)
59 (40%)
23 (15%)
44 (30%) |
63 (72%)
10 (11%)
3 (3%)
12 (14%) |
<0.001 |
|
149 (100%) |
88 (100%) |
| Insertive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
16 (10%)
55 (34%)
26 (16%)
65 (40%) |
46 (31%)
46 (31%)
39 (26%)
16 (11%) |
<0.001 |
|
162 (100%) |
63 (100%) |
| Frequency of condom use during insertive anal
intercourse:** |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
25 (17%)
53 (36%)
22 (15%)
46 (32%) |
70 (69%)
9 (9%)
10 (10%)
12 (12%) |
<0.001 |
| 146 (100%) |
101 (100%) |
* Restricted to men who reported receptive anal
intercourse with a REGULAR partner.
** Restricted to men who reported insertive anal intercourse with
a REGULAR partner.
Table 4:
Comparison of self-reported frequency of
ANAL INTERCOURSE and CONDOM USE
with CASUAL partners among participants in the Vanguard Project
and the Vancouver Lymphadenopathy-AIDS Study (VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Receptive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
71 (38%)
55 (30%)
26 (14%)
33 (18%) |
114 (62%)
49 (27%)
16 (9%)
5 (3%) |
<0.001 |
|
185 (100%) |
184 (100%) |
| Frequency of condom use during receptive anal
intercourse:* |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
7 (6%)
52 (46%)
25 (22%)
30 (26%) |
41 (59%)
9 (13%)
3 (4%)
17 (24%) |
<0.001 |
|
114 (100%) |
70 (100%) |
| Insertive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
59 (32%)
59 (32%)
13 (7%)
29 (54%) |
72 (39%)
58 (32%)
42 (23%)
12 (6%) |
<0.001 |
|
185 (100%) |
184 (100%) |
| Frequency of condom use during insertive anal
intercourse:** |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
8 (6%)
58 (46%)
12 (10%)
48 (38%) |
65 (58%)
17 (15%)
11 (10%)
19 (17%) |
<0.001 |
|
126 (100%) |
112 (100%) |
* Restricted to men who reported receptive anal
intercourse with a CASUAL partner.
** Restricted to men who reported insertive anal intercourse with
a CASUAL partner.
Table 5:
Comparison of self-reported
SUBSTANCE USE
among participants in the Vanguard Project and the Vancouver Lymphadenopathy-AIDS
Study (VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Tobacco: |
|
No:
Yes:
Stopped: |
104 (44%)
110 (47%)
20 (9%) |
90 (34%)
115 (44%)
58 (22%) |
<0.001 |
|
234 (100%) |
263 (100%) |
| Alcohol: |
|
No:
Yes: |
17 (7%)
218 (93%) |
30 (11%)
233 (89%) |
0.112 |
|
235 (100%) |
263 (100%) |
| Cocaine: |
|
No:
Yes: |
164 (70%)
70 (30%) |
241 (92%)
22 (8%) |
<0.001 |
|
234 (100%) |
263 (100%) |
| LSD: |
|
No:
Yes: |
183 (79%)
50 (21%) |
254 (97%)
9 (3%) |
<0.001 |
|
233 (100%) |
263 (100%) |
| Heroin: |
|
No:
Yes: |
226 (97%)
6 (3%) |
263 (100%)
0 (0%) |
0.010* |
|
232 (100%) |
263 (100%) |
| MDA: |
|
No:
Yes: |
194 (83%)
39 (17%) |
236 (90%)
27 (10%) |
0.034 |
|
233 (100%) |
263 (100%) |
| Speed (Amphetamine): |
|
No:
Yes: |
206 (89%)
25 (11%) |
261 (99%)
2 (1%) |
<0.001 |
|
231 (100%) |
263 (100%) |
| Marijuana: |
|
No:
Yes: |
80 (34%)
155 (66%) |
105 (40%)
158 (60%) |
0.175 |
|
235 (100%) |
263 (100%) |
| Poppers: |
|
No:
Yes: |
154 (66%)
78 (34%) |
150 (57%)
113 (43%) |
0.033 |
|
232 (100%) |
263 (100%) |
* Fisher's exact test.
Table 6:
Comparison of
DEMOGRAPHIC CHARACTERISTICS
between participants in the Vanguard Project and participants
aged 18 to 30 in the Vancouver Lymphadenopathy-AIDS Study (VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Age (at baseline visit): |
|
Median:
Range: |
26 years
18-30 yrs |
27 years
18-30 yrs |
<0.001* |
| Ethnicity: |
|
Caucasian:
Other: |
176 (75%)
59 (25%) |
81 (99%)
1 (1%) |
<0.001 |
| Income: |
|
< 10,000:
> 10,000: |
48 (21%)
178 (79%) |
28 (34%)
54 (66%) |
0.020 |
| Education (attended university): |
|
No:
Yes: |
148 (65%)
80 (35%) |
58 (71%)
24 (29%) |
0.038 |
*Wilcoxon rank-sum test.
Table 7:
Comparison of self-reported
NUMBERS of SEXUAL PARTNERS
between participants in the Vanguard Project and participants
aged 18 to 30 in the Vancouver Lymphadenopathy-AIDS Study (VLAS)
|
VP
(n=235) |
VLAS
(n=82) |
p-value |
| Number of sexual partners during the past
year: |
|
Mean:
Standard deviation:
Median:
Range: |
15.2
32.5
5
0-400 |
12.3
27.1
4
0-196 |
0.044 |
| Number of REGULAR sexual partners during the
past year: |
|
Mean:
Standard deviation:
Median:
Range: |
1.7
2.8
1
0-30 |
0.7
0.7
1
0-3 |
<0.001 |
| Number of CASUAL sexual partners during the
past year: |
|
Mean:
Standard deviation:
Median:
Range: |
12.5
21.2
4
0-120 |
11.6
27.1
3
0-194 |
0.084 |
Table 8:
Comparison of self-reported frequency of
ANAL INTERCOURSE and CONDOM USE
with REGULAR partners among participants in the Vanguard Project
and participants aged 18 to 30 in the Vancouver Lymphadenopathy-AIDS
Study (VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Receptive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
13 (8%)
63 (39%)
27 (17%)
59 (36%) |
12 (25%)
21 (44%)
13 (27%)
2 (4%) |
<0.001 |
|
162 (100%) |
48 (100%) |
| Frequency of condom use during receptive anal
intercourse:* |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
23 (15%)
59 (40%)
23 (15%)
44 (30%) |
24 (67%)
6 (17%)
2 (6%)
4 (11%) |
<0.001 |
|
149 (100%) |
36 (100%) |
| Insertive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
16 (10%)
55 (34%)
26 (16%)
65 (40%) |
14 (29%)
18 (38%)
12 (25%)
4 (8%) |
<0.001 |
|
162 (100%) |
48 (100%) |
| Frequency of condom use during insertive anal
intercourse:** |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
25 (17%)
53 (36%)
22 (15%)
46 (32%) |
24 (71%)
2 (6%)
5 (15%)
3 (9%) |
<0.001 |
|
146 (100%) |
34 (100%) |
* Restricted to men who reported receptive anal
intercourse with a REGULAR partner.
** Restricted to men who reported insertive anal intercourse with
a REGULAR partner.
Table 9:
Comparison of self-reported frequency of
ANAL INTERCOURSE and CONDOM USE
with CASUAL partners among participants in the Vanguard Project
and participants aged 18 to 30 in the Vancouver Lymphadenopathy-AIDS
Study (VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Receptive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
71 (38%)
55 (30%)
26 (14%)
33 (18%) |
31 (51%)
22 (36%)
7 (11%)
1 (2%) |
0.011 |
| |
185 (100%) |
184 (100%) |
|
| Frequency of condom use during receptive anal
intercourse:* |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
7 (6%)
52 (46%)
25 (22%)
30 (26%) |
19 (63%)
3 (10%)
2 (7%)
6 (20%) |
<0.001
|
| |
114 (100%) |
30 (100%) |
|
| Insertive anal intercourse: |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
59 (32%)
59 (32%)
13 (7%)
54 (29%) |
24 (39%)
18 (30%)
17 (28%)
2 (3%) |
<0.001 |
| |
185 (100%) |
61 (100%) |
|
| Frequency of condom use during insertive anal
intercourse:** |
|
Never:
< 30% of sexual encounters:
30-70% of sexual encounters:
> 70% of sexual encounters: |
8 (6%)
58 (46%)
12 (10%)
48 (38%) |
26 (70%)
4 (11%)
5 (14%)
2 (5%) |
<0.001 |
| |
126 (100%) |
37 (100%) |
|
* Restricted to men who reported receptive anal
intercourse with a CASUAL partner.
** Restricted to men who reported insertive anal intercourse with
a CASUAL partner.
Table 10:
Comparison of self-reported
SUBSTANCE USE
among participants in the Vanguard Project and participants aged
18 to 30 in the Vancouver Lymphadenopathy-AIDS Study (VLAS)
|
Vanguard
n (%) |
VLAS
n (%) |
p-value |
| Tobacco: |
|
No:
Yes:
Stopped: |
104 (44%)
110 (47%)
20 (9%) |
26 (32%)
43 (52%)
13 (16%) |
0.053 |
|
234 (100%) |
82 (100%) |
| Alcohol: |
|
No:
Yes: |
17 (7%)
218 (93%) |
4 (5%)
82 (95%) |
0.460 |
|
235 (100%) |
263 (100%) |
| Cocaine: |
|
No:
Yes: |
164 (70%)
70 (30%) |
72 (88%)
10 (12%) |
<0.001 |
|
234 (100%) |
82 (100%) |
| LSD: |
|
No:
Yes: |
183 (79%)
50 (21%) |
79 (96%)
3 (4%) |
<0.001 |
|
233 (100%) |
82 (100%) |
| Heroin: |
|
No:
Yes: |
26 (97%)
6 (3%) |
82 (100%)
0 (0%) |
0.346* |
|
232 (100%) |
82 (100%) |
| MDA: |
|
No:
Yes: |
194 (83%)
39 (17%) |
71 (87%)
11 (13%) |
0.479 |
|
233 (100%) |
82 (100%) |
| Speed (Amphetamine): |
|
No:
Yes: |
206 (89%)
25 (11%) |
80 (98%)
2 (2%) |
0.020 |
|
231 (100%) |
263 (100%) |
| Marijuana: |
|
No:
Yes: |
80 (34%)
155 (66%) |
35 (43%)
47 (57%) |
0.161 |
|
235 (100%) |
82 (100%) |
| Poppers: |
|
No:
Yes: |
154 (66%)
78 (34%) |
54 (66%)
28 (34%) |
0.931 |
|
232 (100%) |
82 (100%) |
*Fisher's exact test.
|
