Because the emergence of highly active antiretroviral therapy (HAART), the availability of life-prolonging treatments has made the durable suppression of HIV the primary goal of treatment. Morbidity and mortality have decreased with the advent of these new anti-HIV therapies.1-5 However, despite the clinical improvement of treated HIV-infected patients, the impact of HAART on physical condition and overall well-being has become a major concern. In particular, health-related quality of life (HRQL) has been identified as a key component in the overall health of HIV-infected patients.6 HIV is increasingly regarded as a chronic illness, possibly associated with comorbidities.7
The impact of HAART on risky sexual behavior is still a matter of debate. Although the number of new cases of HIV infection has decreased among the injection drug user population, the occurrence of HIV infection among gay men continues to account for a large proportion of new infections.8,9 Unsafe sex is therefore still common among gay men10,11 and HIV-positive men.12
More specifically, in France, repeated cross-sectional studies published in the gay press have shown that the prevalence of unsafe sex among gay populations has varied very little from the 1985 level of approximately 20%.13 This finding indicates that although patients' associations have been playing an active role in the gay community, prevention is still an issue among this population. One serious limitation of studies of this kind is the recruitment bias introduced by the means used to reach the target population. In the majority of the studies, men who are recruited either at gay sexual venues or via the gay press might represent the least safe segment of the gay population as a whole. Another limitation is the fact that they do not deal with an exclusively HIV-infected population, and to our knowledge, no studies have been conducted so far on a representative sample of HIV-infected gay men.
The aim of this study was therefore to determine the factors associated with unsafe sex in a representative sample of French HIV-infected gay men. In particular, we chose to distinguish factors related to sexual lifestyle, those related to disease progression and treatment, and, finally, subjective health outcomes such as HRQL, for which standardized methods of assessment are now available.6
In 2003, the French National Agency of AIDS Research (ANRS, France) supported a national cross-sectional survey conducted among a random stratified sample of people living with HIV/AIDS (PLWHAs), recruited at 102 French hospital departments delivering HIV care. Its aim was to describe the living and socioeconomics conditions of PLWHAs in France. The stratification criteria were the hospital departments' geographic location and the HIV caseload. Eligible subjects were outpatients at least 18 years of age and who had been diagnosed with HIV-1 at least 6 months previously. Those who were foreign citizens had to have been living in France for at least 6 months. At each participating hospital, participation in the survey was proposed to each eligible outpatient at the end of their consultation, whether they were attending a regular or a special HIV-related appointment. The participants gave their written informed consent and were each given a 15-euro voucher. In addition, the sample size was proportional to the number of HIV-infected patients being followed in the unit.
Patients who agreed to participate answered a face-to-face questionnaire (398 closed-ended questions) administered by a trained interviewer using the CAPI (Computer-assisted Personal Interview) system. They were then asked to fill in a self-administered questionnaire. The first questionnaire dealt with a range of aspects of the daily life of PLWHAs and their socioeconomic conditions. The second questionnaire was used to assess the respondents' HRQL. In parallel, the consulting physician completed a short medical questionnaire.
This analysis was restricted to male patients who defined themselves as homosexual or bisexual, who declared that they had had at least 1 male sexual partner during the previous 12 months and who had completed the HRQL Scale questionnaire included in the self-administered questionnaire.
Sexual Behavior-Related Characteristics
The following characteristics of the respondents' sexual life were collected: number of male and female partners during their lifetime and during the previous 12 months, existence of a steady partner, bisexual behavior during the previous 12 months, and frequency of sexual intercourse during the previous 4 weeks. Specific questions about the use of condoms with the steady partner and casual partners were also asked, as well as 7 reasons for not having used condoms (you forgot; you feel your partners are responsible for protecting themselves; your partner[s] is [are] also HIV positive; your viral load is undetectable; you or your partner[s] have difficulty in using condoms or refuse to do so; using a condom betrays the fact that you are seropositive; or you rely on preventive postexposure treatment). In addition, there were 6 yes/no questions about the means used to find sexual partners during the previous 12 months: ad columns, Internet/phone networks, saunas/backrooms/sex clubs, bars/discos, encounters via friends/associations/work, or outdoor places of sexual encounter.
Unsafe sex was defined as having had at least 1 episode of anal intercourse without a condom with a casual partner during the previous 12 months.
Patients were asked whether they had used any psychoactive substances (cannabis, ecstasy, heroine, cocaine, amphetamines, or poppers) during the previous 12-month period (never/sometimes/regularly/every day). Consumption of stimulating substances was defined as the use of ecstasy and/or cocaine and/or amphetamines at least once during the previous 12 months. Because alcohol is commonly consumed, only binge drinking (defined as taking at least 6 alcoholic drinks on a single occasion) was taken into consideration.
Health-Related Quality of Life
The self-administered questionnaire included the Medical Outcome Study Short-Form Health Survey (SF-36)14-16 validated in French,17-19 which involves a scale designed to analyze 8 health aspects: 4 relating to the physical quality of life (physical functioning, bodily pain, physical-related role limitation, and general health) and 4 relating to the mental quality of life (vitality, social functioning, emotional-related role limitation, and general mental health). All 8 HRQL scores were dichotomized, taking as the threshold the 25th percentile of the distribution by age and sex of each score in the general French population.17,20 All patients obtaining a score below the threshold value were classified as "low HRQL" patients. In addition, to obtain an overall assessment of physical HRQL and mental HRQL, we counted the number of aspects with a low score. Poor physical/mental HRQLs were defined as having at least 1 physical/mental aspect with a low score in comparison with the general French population. This method has been described in a previous study.21 In addition, the number of mental dimensions that were considered as low was summed up. To have a continuous measure of HRQL, the physical component summary (PCS) and the mental component summary (MCS) aggregate scores were computed.16,19
The medical questionnaire included information about each patent's viral load, CD4 cell count, clinical stage, time of diagnosis, and HIV treatment.
Among the subsample of patients who declared having had intercourse with casual partners during the previous 12 months, the sociodemographic and clinical characteristics of patients who completed the HRQL questionnaire (HRQL respondents) were compared with those of patients who did not complete this questionnaire (HRQL nonrespondents). Second, the practice of unsafe sex with casual partners was analyzed among the HRQL respondents. χ2 Tests were used to compare patients practicing unsafe sex with those who did not behave in this way. To identify the factors independently associated with unsafe sex, and especially to test the impact of mental HRQL, logistic models were used. A stepwise procedure was used here to select statistically significant factors in a multivariate model (entry threshold, P < 0.20). Statistical analyses were performed using the SPSS v 12.0.1 software program (SPSS, Inc, Chicago, IL).
Among the 4963 eligible patients, 264 were not solicited because their physician considered that their physical or psychological conditions were not compatible with participation in the survey, whereas 1767 patients refused to participate (2932 participants; participation rate, 59%). Patients most frequently explained their refusal by a lack of time. Nonparticipants were not significantly different from participants in terms of sex, age, viral load, or CD4 lymphocyte count.
Among the 2932 participants in the VESPA survey, 1117 male patients declared that they were homosexual or bisexual. Of this group, 13.6% reported having no male partners during the previous 12 months. Among the remaining 965 patients, 265 (27.5%) had intercourse with a steady partner only, 399 (41.3%) with casual partners only, and 301 (31.2%) with both. Our analysis focused on the 700 patients who had intercourse with casual partners during the previous 12 months. We excluded from the analysis 24 participants diagnosed HIV-infected for less than 12 months (because among them, risky sexual behavior during the previous 12 months may have occurred before diagnosis).
Of the remaining 676 patients, 85 produced incomplete HRQL data. No significant differences were found to exist between the 591 HRQL respondents and the 85 HRQL nonrespondents in terms of age, employment, education, plasma viral load, CD4 cell count, or clinical stage. We therefore conducted our analysis on the 591 HRQL respondent patients.
In our selected population of 591 gay men, the mean age was 43 years, 269 patients (46%) had graduated at least from high school, and 371 (63%) were employed. Nearly half of the patients reported having a stable partnership (n = 257, 43%). One patient out of 10 (n = 58) declared having had bisexual relationships during the previous 12 months, 68 had a history of prostitution, and the median number of sexual partners reported during the previous year was 10. The main places used to find partners were saunas, backrooms, and sex clubs (n = 306, 52%); bars/discos (n = 252, 43%); outdoor sexual places of encounter (n = 245, 42%); and via the Internet/phone network (n = 184, 31%). Only 118 patients (20%) met partners in their social network (via friends/associations/work), and 88 (15%) used ad columns.
Substance use was frequent: more than 40% (n = 260) reported using poppers; nearly one third used cannabis (n = 183), and more than 10% declared that they indulged in binge drinking at least once a month (n = 77). The use of anxiolytics use was also frequent (n = 136, 23%).
More than one third of the study population was diagnosed as having HIV after 1995 (n = 203, 34%). From the medical point of view, 476 (81%) were HAART treated, 132 (22%) were in the CDC clinical stage C of the illness, 374 (63%) had an undetectable viral load (<400 copies/mL), and 519 (88%) had a CD4 cell count of more than 200/mL.
Physical HRQL was rather low in the study population (Table 1). On each physical subscale, the proportion of patients obtaining a low score (in comparison with the general French population) ranged from 36%, in the case of the bodily pain scale, to 60% in that of the general health perception scale. Using the overall indicator, 74% of them were found to have poor physical HRQL (defined as at least 1 subscale with a low score in comparison with the general French population). The PCS mean score was 51 (SD, 8).
As far as the mental HRQL was concerned, nearly 50% of the patients obtained a low score on each of the subscales. Poor mental HRQL (defined in a similar way to the physical HRQL) was observed in 68% of all the patients included in the study. The MCS mean score was 49 (SD, 10).
Unsafe Sex With Casual Partners
Among the 591 patients selected, 117 (20%) reported having had at least 1 episode of unprotected anal intercourse with casual partners. The main reasons put forward for not using condoms were difficulty in using a condom or refusal to do so (n = 51, 44%), seropositive partners (n = 41, 35%), and the fact that the respondent's own viral load was undetectable (n = 26, 22%). Fifteen percent of the patients felt that their partners were responsible for protecting themselves (n = 18), 8% forgot (n = 9), 5% were afraid that using a condom would disclose their seropositivity (n = 6), and 3% relied on preventive postexposure treatment (n = 3).
Neither the patients' sociodemographic variables (age, etc) nor having a steady partner nor having had sex with both men and women during the previous 12 months was found to be associated with unsafe sex. Table 1 shows the main factors found to be associated with unsafe sex: having had intercourse with more than 15 partners during the previous 12 months, having met sexual partners via the Internet/phone network or in saunas/backrooms/sex clubs, and having occasionally used cannabis, taken part in binge drinking, or used anxiolytics or poppers during the previous 12 months. By contrast, safer sex was more frequently associated with patients who encountered sexual partners via friends/associations/work. None of the other strategies used to search for partners were found to be significant factors. Nor were any of the outcomes accounting for disease progression associated with unsafe sex.
We also analyzed the impact of psychological data on unsafe practices.
The associations between the 4 physical HRQL subscales and unsafe sex were analyzed (Table 1). Patients reporting unsafe sexual behavior more often had less limited physical activities than patients adopting consistently safe sexual behavior. No such differences were observed in the case of the other 3 physical subscales. This was also shown to be true when using the dichotomous indicator of poor physical health or the PCS score.
On each of the mental subscales, significant associations were found to exist with unsafe sex. The strongest association was that between unsafe sex and having a low score on the social functioning subscale (P = 0.001). The number of mental subscales with low scores was linearly associated with a higher risk of unsafe sex (P = 0.003). Using the overall index to mental HRQL, having a poor mental HRQL was also found to be very significantly associated with unsafe practices (P < 0.01). Lastly, a strong association was found when using the MCS score (P < 0.01).
In the multivariate model (Table 2), having a poor mental HRQL was also independently associated with having unsafe sex with casual partners. Other independent factors positively associated with unsafe sex were frequenting a large number of partners during the previous 12 months, using the Internet or phone network as a means of contacting partners, binge drinking, and the use of anxiolytics during the previous 12 months. The only protective factor found in the multivariate analysis to be significantly associated with the outcome was encountering sexual partners via friends/associations/work networks. A similar set of predictors was obtained in the final model when the dichotomous variable defining mental HRQL was substituted by the number of mental subscales with low scores (adjusted odd ratio, 1.2; 95% confidence interval, 1.1-1.3 per unit increase).
In the context of the relapses occurring these days in gay male circles in many Western countries, the aim of this study was to determine the main factors associated with unsafe sex with casual partners among HIV-positive gay men. To have a homogenous study population exposed to comparable situations of risk taking, we chose to restrict our sample to patients who reported at least 1 casual partner, excluding those who reported no male partner and those who only reported a steady partner. Factors of several kinds were investigated: clinical, psychosocial, and behavioral factors, as well as factors relating to various kinds of substance consumption. Furthermore, to be comparable with other studies, we utilized a commonly used definition of unsafe sex.22-28
Some factors previously reported to be associated with sexual risk behavior in studies on gay men were also included in our study. The results confirmed that unsafe sex with casual partners is significantly associated with the number of partners, binge drinking, and anxiolytic consumption.28-32 We also established that various types of strategies used to meet sexual partners33-36 are associated with unsafe sex. The Internet constitutes a new sexual risk environment, and subsequent studies are now required to investigate how the Internet might be used to promote both safer sex behavior36 and HIV prevention in high-risk homosexual populations.37 By contrast, our results show that patients who seek partners via their social network (friends, work, and associations) tend less frequently to engage in unsafe practices. Among HIV-positive gay men, unsafe sex was not found here to be correlated with the subjects' sociodemographic characteristics, in line with previous studies.10,38
The main contribution of the present study is the fact that it outlines some specific HIV-related factors. In particular, unsafe sex was found to be significantly correlated with a poor mental HRQL. This finding seems to be particularly important because of the fact that, among HIV-infected people, HAART seems to restore mental HRQL less effectively than physical HRQL.21 This result is also consistent with other studies showing that sexual risk behavior is associated with mental disorders.29,39-41 In a sample of patients with HAART resistance, mental disorder was found to be an independent predictor of sexual risk behavior.12 The present study, which, to our knowledge, was the first ever conducted on a population of HIV-positive gay men, shows the existence of a highly significant association between the mental aspects of HRQL and unsafe sex. We used a dichotomous measure of mental HRQL that had already been used in another study focused on HIV-infected individuals.21 This measure was able to summarize all dimensions of mental HRQL. Furthermore, we were able to show that sexual risk behavior was linearly associated with the number of impaired mental dimensions of HRQL.
Previous studies have shown that the symptoms induced by treatment can have major effects on treated patients' HRQL.21,42 Moreover, several studies conducted on HIV-infected patients have shown the existence of a correlation between the side effects of treatment and sexual risk taking.28,43 It therefore seems likely that the side effects of treatment may constitute 1 of the main components of mental HRQL, but this hypothesis still requires confirmation through further investigations.
In our study, none of the characteristics of disease progression or response to treatment were found to be associated with unsafe sex. This is a fundamental point, in view of the discrepancies existing between previous findings published in literature. Several studies had shown that unsafe sex was either associated44,45 or not associated46,47 with optimum viral suppression as well as with perception of sexual risk behavior.48,49
Some of the limitations of our study obviously have to be acknowledged. First, our study shares with many others some of the general methodological problems related to risky sexual behavior assessment based on patients' declarations, which may be affected by social desirability bias. However, several studies have shown that such methods are very reliable, and they have been widely used in several countries.50 Neither did we have any precision on the type of anal sex, that is, insertive or receptive. The way our questionnaire was administered-face-to-face and not self-administered-made it difficult to ask such type of questions.
Second, we adopted a predictive approach based on cross-sectional data to assess the HRQL, whereas longitudinal data might have been more appropriate for examining the personal trajectory of individuals in terms of their HRQL. However, the VESPA survey provides a valuable complement to the existing longitudinal data: this is the first survey ever conducted in France on a large, representative random sample of HIV-infected outpatients.
Third, assessment of HRQL using the SF-36 refers to the 4 preceding weeks. We, on the other hand, measured unsafe sex during the 12 preceding months, and consequently, our results may be affected because of the difference in time. Nevertheless, HRQL has been shown to be relatively stable over time.42
A fourth limitation relates to possible bias caused by HRQL nonresponses. Health-related quality-of-life nonrespondents were excluded from our analysis, which raises concerns about the generalization of our data. Nevertheless, these patients were not different in terms of sociodemographics and medical outcomes, limiting the possibility of selection bias.
In conclusion, a poor mental HRQL was found in the present study to be strongly associated with unsafe sex with casual partners among HIV-infected homosexuals. This finding has important public health implications in terms of secondary prevention. It therefore appears necessary in the future to take into account HIV-infected patients' mental HRQL during their long-term follow-up, to optimize secondary prevention.
1. Allardice GM, McMenamin JJ, Parpia T, et al. The recent impact of antiretroviral combination therapy on CD4 counts, AIDS and death in HIV-infected persons: routine HIV surveillance in Scotland. Int J STD AIDS
2. Allen LL, Haririfar M, Cohen J, et al. Quality of life and locus of control of migraineurs. Clin Excell Nurse Pract
3. CASCADE T Collaboration. Survival after introduction of HAART in people with known duration of HIV-1 infection. Lancet
4. Mocroft A, Vella S, Benfield T, et al. Changing patterns of mortality across Europe in patients infected with HIV-1. Lancet
5. Sabin CA. The changing clinical epidemiology of AIDS in the highly active antiretroviral therapy era. AIDS
. 2002;16(suppl 4):S61-S68.
6. Wu AW. Quality of life assessment comes of age in the era of highly active antiretroviral therapy. AIDS
7. Vigouroux C, Gharakhanian S, Salhi Y, et al. Adverse metabolic disorders during highly active antiretroviral treatments (HAART) of HIV disease. Diabetes Metab
8. INVS. Premiers résultats du nouveau dispositif de depistage de l'infection par le VIH. Bulletin d'Epidemiologie Hebdomadaire
9. Lert F, Obadia Y, Group V. First result ANRS/VESPA study among representative sample of HIV-infected people. Rev Epidemiol Santé Publique
10. Beck A, McNally I, Petrak J. Psychosocial predictors of HIV/STI risk behaviours in a sample of homosexual men. Sexual Transmitted Infectious
11. Strathdee SA, Martindale SL, Cornelisse PG, et al. HIV infection and risk behaviours among young gay and bisexual men in Vancouver. CMAJ
12. Kozal MJ, Amico KR, Chiarella J, et al. Antiretroviral resistance and high-risk transmission behavior among HIV-positive patients in clinical care. AIDS
13. Bochow M, Jauffret-Roustide M, Michel A, et al. Les évolutions des comportements sexuels et les modes de vie à travers les enquêtes réalisées dans la presse gay en France (1985-2000). In: Broqua C, Lert F, Souteyrand Y, eds. Homosexualités au Temps du Sida. Tensions Sociales et Identitaires
. Paris: Collection Sciences sociales et Sida, 2003:35-54.
14. McHorney CA, Ware JE Jr, Lu JF, et al. The MOS 36-Item Short-Form Health Survey (SF-36): III. Tests of data quality, scaling assumptions, and reliability across diverse patient groups. Med Care
15. McHorney CA, Ware JE Jr, Raczek AE. The MOS 36-Item Short-Form Health Survey (SF-36): II. Psychometric and clinical tests of validity in measuring physical and mental health constructs. Med Care
16. Ware JE Jr, Sherbourne CD. The MOS 36-Item Short-Form Health Survey (SF-36). I. Conceptual framework and item selection. Med Care
17. Leplege A, Ecosse E, Pouchot J, et al eds. Le Questionnaire MOS SF-36: Manuel de L'utilisateur et Guide d'Interprétation des Scores
. Paris: Estem, 2001.
18. Leplege A, Mesbah M, Marquis P. Preliminary analysis of the psychometric properties of the French version of an international questionnaire measuring the quality of life: the MOS SF-36 (version 1.1). Rev Epidemiol Sante Publique
19. Ware JE Jr, Kosinski M, Bayliss MS, et al. Comparison of methods for the scoring and statistical analysis of SF-36 health profile and summary measures: summary of results from the Medical Outcomes Study. Med Care
. 1995;33(4 suppl):AS264-AS279.
20. Leplege A, Ecosse E, Verdier A, et al. The French SF-36 Health Survey: translation, cultural adaptation and preliminary psychometric evaluation. J Clin Epidemiol
21. Carrieri P, Spire B, Duran S, et al. Health-related quality of life
after 1 year of highly active antiretroviral therapy. J Acquir Immune Defic Syndr
. 2003;1 32(1):38-47.
22. Amirkhanian YA, Kelly JA, Kabakchieva E, et al. A randomized social network HIV prevention trial with young men who have sex with men in Russia and Bulgaria. AIDS
23. Hart TA, Wolitski RJ, Purcell DW, et al. Partner awareness of the serostatus of HIV-seropositive men who have sex with men: impact on unprotected sexual behavior
. AIDS Behav
24. Kalichman SC, Nachimson D, Cherry C, et al. AIDS treatment advances and behavioral prevention setbacks: preliminary assessment of reduced perceived threat of HIV-AIDS. Health Psychol
25. Kelly JA, Kalichman SC. Reinforcement value of unsafe sex as a predictor of condom use and continued HIV/AIDS
risk behavior among gay and bisexual men. Health Psychol
26. Martin JI, Pryce JG, Leeper JD. Avoidance coping and HIV risk behavior among gay men
. Health Soc Work
27. Stolte IG, de Wit JB, van Eeden A, et al. Perceived viral load, but not actual HIV-1-RNA load, is associated with sexual risk behaviour among HIV-infected homosexual men. AIDS
28. Vincent E, Bouhnik AD, Carrieri MP, et al. Impact of HAART-related side effects on unsafe sexual behaviours in HIV-infected injecting drug users: 7-year follow up. AIDS
29. Bouhnik AD, Moatti JP, Vlahov D, et al. Highly active antiretroviral treatment does not increase sexual risk behaviour among French HIV infected injecting drug users. J Epidemiol Community Health
30. Carey MP, Carey KB, Maisto SA, et al. Prevalence and correlates of sexual activity and HIV-related risk behavior among psychiatric outpatients. J Consult Clin Psychol
31. McKirnan DJ, Vanable PA, Ostrow DG, et al. Expectancies of sexual "escape" and sexual risk among drug and alcohol-involved gay and bisexual men. J Subst Abuse
32. Purcell DW, Parsons JT, Halkitis PN, et al. Substance use and sexual transmission risk behavior of HIV-positive men who have sex with men. J Subst Abuse
33. Crosby R, Mettey A. A descriptive analysis of HIV risk behavior among men having sex with men attending a large sex resort. J Acquir Immune Defic Syndr
34. Elford J, Bolding G, Sherr L. Seeking sex on the Internet and sexual risk behaviour among gay men
using London gyms. AIDS
35. Elford J, Bolding G, Sherr L. High-risk sexual behaviour increases among London gay men
between 1998 and 2001: what is the role of HIV optimism? AIDS
36. Mettey A, Crosby R, DiClemente RJ, et al. Associations between Internet sex seeking and STI associated risk behaviours among men who have sex with men. Sex Transm Infect
37. Elford J, Bolding G, Davis M, et al. The Internet and HIV study: design and methods. BMC Public Health
38. Robins AG, Dew MA, Davidson S, et al. Psychosocial factors associated with risky sexual behavior
among HIV-positive gay men
. AIDS Behav
39. Hutton HE, Lyketsos CG, Zenilman JM, et al. Depression and HIV risk behaviors among patients in a sexually transmitted disease clinic. Am J Psychiatry
40. Shi J. Depression severity and HIV risk behavior. Am J Psychiatry
. 2004;161(5):929. [author reply, 929-930].
41. Strathdee SA, Hogg RS, Martindale SL, et al. Determinants of sexual risk-taking among young HIV-negative gay and bisexual men. J Acquir Immune Defic Syndr
42. Preau M, Leport C, Salmon-Ceron D, et al. Health-related quality of life
and patient-provider relationships in HIV-infected patients during the first three years after starting PI-containing antiretroviral treatment. AIDS Care
43. Desquilbet L, Deveau C, Goujard C, et al. Increase in at-risk sexual behaviour among HIV-1-infected patients followed in the French PRIMO cohort. Aids
44. Dukers NH, Goudsmit J, de Wit JB, et al. Sexual risk behaviour relates to the virological and immunological improvements during highly active antiretroviral therapy in HIV-1 infection. AIDS
45. Ven PV, Mao L, Fogarty A, et al. Undetectable viral load is associated with sexual risk taking
in HIV serodiscordant gay couples in Sydney. AIDS
46. Vanable PA, Ostrow DG, McKirnan DJ. Viral load and HIV treatment attitudes as correlates of sexual risk behavior among HIV-positive gay men
. J Psychosom Res
47. Wolf K, Young J, Rickenbach M, et al. Prevalence of unsafe sexual behavior
among HIV-infected individuals: the Swiss HIV Cohort Study. J Acquir Immune Defic Syndr
48. Ostrow DE, Fox KJ, Chmiel JS, et al. Attitudes towards highly active antiretroviral therapy are associated with sexual risk taking
among HIV-infected and uninfected homosexual men. AIDS
49. Suarez TP, Kelly JA, Pinkerton SD, et al. Influence of a partner's HIV serostatus, use of highly active antiretroviral therapy, and viral load on perceptions of sexual risk behavior in a community sample of men who have sex with men. J Acquir Immune Defic Syndr
50. Spira A, Bajos N, Giami A, et al. Cross-national comparisons of sexual behavior
surveys-methodological difficulties and lessons for prevention. Am J Public Health