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Biomedical subjects

S A Strathdee

Publications and source records attributed to S A Strathdee.

At least 55 records · Page 3Linked to original sources
PubMed1998

Determinants of sexual risk-taking among young HIV-negative gay and bisexual men.

Data from a cohort of young HIV-negative gay and bisexual men were analyzed to identify determinants of sexual risk-taking at baseline. Gay/bisexual men aged between 18 and 30 completed a self-administered questionnaire including demographics, depression, social support, substance use, and consensual versus nonconsensual sex. Risk-takers were defined as those who had unprotected anal sex with casual male sex partners in the previous year; non-risk-takers were defined as those who reported consistent condom use during anal sex with all male partners in the previous year. Logistic regression was used to identify independent predictors of sexual risk-taking. Of 439 men studied, risk-takers had less education, a higher depression score, less social support, and were more likely to report nonconsensual sex and recreational drug use relative to non-risk-takers. Independent predictors of sexual risk-taking were low education, nitrite use, low social support (adjusted odds ratio [AOR]=1.65; 95% CI, 1.04-2.59), and nonconsensual sex experienced as a youth or adult (AOR=1.85; 95% CI, 1.15-2.96). Young gay/bisexual men reporting nonconsensual sex, low social support, or nitrite use were significantly more likely to have recently had unprotected anal sex with casual partners. HIV prevention programs aimed at young gay/bisexual men should include sexual abuse counselling and foster community norms supporting safer sex practices.

Adult↗
PubMed1998

Barriers to use of free antiretroviral therapy in injection drug users.

CONTEXT: In British Columbia, human immunodeficiency virus (HIV)-infected persons eligible for antiretroviral therapy may receive it free but the extent to which HIV-infected injection drug users access it is unknown. OBJECTIVE: To identify patient and physician characteristics associated with antiretroviral therapy utilization in HIV-infected injection drug users. DESIGN: Prospective cohort study with record linkage between survey data and data from a provincial HIV/AIDS (acquired immunodeficiency syndrome) drug treatment program. SETTING: British Columbia, where antiretroviral therapies are offered free to all persons with HIV infection with CD4 cell counts less than 0.50 x 10(9)/L (500/microL) and/or HIV-1 RNA levels higher than 5000 copies/mL. SUBJECTS: A total of 177 HIV-infected injection drug users eligible for antiretroviral therapy, recruited through the prospective cohort study since May 1996. MAIN OUTCOME MEASURES: Patient use of antiretroviral drugs through the provincial drug treatment program and physician experience treating HIV infection. RESULTS: After a median of 11 months after first eligibility, only 71 (40%) of 177 patients had received any antiretroviral drugs, primarily double combinations (47/71 [66%]). Both patient and physician characteristics were associated with use of antiretroviral drugs. After adjusting for CD4 cell count and HIV-1 RNA level at eligibility, odds of not receiving antiretrovirals were increased more than 2-fold for females (odds ratio [OR], 2.53; 95% confidence interval [CI], 1.08-5.93) and 3-fold for those not currently enrolled in drug or alcohol treatment programs (OR, 3.49; 95% CI, 1.45-8.40). Younger drug users were less likely to receive therapy (OR, 0.47/10-y increase; 95% CI, 0.28-0.80). Those with physicians having the least experience treating persons with HIV infection were more than 5 times less likely to receive therapy (OR, 5.55; 95% CI, 2.49-12.37). CONCLUSIONS: Despite free antiretroviral therapy, many HIV-infected injection drug users are not receiving it. Public health efforts should target younger and female drug users, and physicians with less experience treating HIV infection.

Adult↗
PubMed1998

Is AIDS a floating point between HIV seroconversion and death? Insights from the Tricontinental Seroconverter Study.

OBJECTIVE: To investigate the significance of the time from seroconversion to AIDS (incubation time) and other covariates for survival from AIDS to death. METHODS: In survival analysis, survival from AIDS to death was compared for different categories of length of incubation time adjusted and unadjusted for other covariates, and significant predictors for survival from AIDS to death were investigated. RESULTS: Survival after AIDS was not affected by the incubation time in univariate as well as in multivariate analyses. Predictive factors for progression from AIDS to death were age at seroconversion, type of AIDS diagnosis, and CD4 cell count at AIDS. The relative hazard for age at seroconversion increased 1.38-fold over 10 years. Men with a CD4 cell count at AIDS of <130 x 10(6)/l had a twofold higher risk in progression to death than men with higher CD4 cell counts. Persons diagnosed with lymphoma had a sixfold higher risk of progression to death than persons with Kaposi's sarcoma or opportunistic infections. CONCLUSIONS: The incubation time as well as other factors before AIDS did not affect survival after AIDS. Survival from AIDS to death can be predicted by data obtained at the time of AIDS diagnosis, such as type of diagnosis, age and CD4 cell count. AIDS seems to be a significant point in progression to death, and not just a floating point between infection and death affected by prior factors for persons who did not receive effective therapy and did not have long incubation times.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Factors associated with frequent needle exchange program attendance in injection drug users in Vancouver, Canada.

The objective of this study was to identify factors associated with frequent needle exchange program (NEP) attendance by injection drug users (IDUs) in Vancouver, Canada. Data were examined from a case control study of recent HIV infection. IDUs with documented HIV seroconversion after January 1, 1994 (n = 89) and seronegative controls with two documented HIV-negative test results in the same period (n = 192) were asked about demographic and social information, drug injection and sexual behavior, and NEP attendance. Logistic regression was used to examine the effect of multiple variables on NEP attendance while adjusting for HIV status and other potential confounders. Frequent (> 1 time/week) versus nonfrequent (< or = 1 time/week) NEP attenders did not differ with respect to gender, age, ethnicity, education, or HIV serostatus. For men, multivariate analysis showed that frequent cocaine injection was the only variable independently associated with NEP attendance (adjusted odds ratio [AOR] = 3.9; 95% confidence interval [CI] = 1.8-8.3); for women, independently associated variables were frequency of any drug injection (AOR = 5.5; 95% CI = 1.7-17), shooting gallery attendance (AOR = 11.5; 95% CI = 2.2-66), and having a nonlegal source of income (AOR = 3.4; 95% CI = 1.0-12). Borrowing used needles was associated with frequent NEP attendance in the univariate analysis. The NEP in Vancouver attracts IDUs who are frequent injectors (especially men using cocaine) and who have high-risk behaviors or an unstable lifestyle. This finding reinforces the role of NEPs as potential focal points for intervention in this hard-to-reach population.

Adult↗
PubMed1998

A qualitative investigation into an HIV outbreak among injection drug users in Vancouver, British Columbia.

The proportion of injection drug users (IDUs) testing positive for Human Immunodeficiency Virus (HIV) in British Columbia has increased from 3 to 7% since January 1993 (Patrick et al., 1997). We conducted a qualitative study as a first step in a case control investigation aimed at identifying risk factors associated with HIV seroconversion. Sixteen subjects participated in in-depth interviews which were transcribed and analysed using grounded theory methods. Three dominant themes emerged: Addiction, Prevention, and Social Determinants. The results suggest that prevention efforts such as the availability of clean needles and condoms are not adequate to combat the complex social determinants of addiction--be they causal or consequential--which in turn contribute to unsafe injection practices.

Adult↗
PubMed1997

Associations of age, immunosuppression, and AIDS among homosexual men in the Tricontinental Seroconverter Study.

To characterize the associations of age, immunosuppression, and AIDS outcomes, we evaluated serial measures of CD4+ lymphocytes from 376 homosexual men with documented dates of HIV-1 seroconversion registered in the Tricontinental Seroconverter Study. Using regression models and adjusting for variation within individuals, we found no association between age and the number of CD4+ lymphocytes at seroconversion or with CD4+ lymphocyte decline after seroconversion. Men who developed opportunistic infections had fewer CD4+ lymphocytes at the time of diagnosis compared with men who developed AIDS-defining Kaposi's sarcoma. Older age was significantly associated with higher numbers of CD4+ lymphocytes in individuals diagnosed with AIDS-defining Kaposi's sarcoma but was not significant for individuals with opportunistic infections. Because older age shortens the latency period of Kaposi's sarcoma and does not affect the CD4+ lymphocyte loss, it results in higher CD4+ lymphocytes at the time of diagnosis. These findings suggest distinct biologic mechanisms for various AIDS manifestations, which is important for clinical decision making and health care planning.

AIDS-Related Opportunistic Infections↗
PubMed1997

Incidence and prognostic significance of symptomatic primary human immunodeficiency virus type 1 infection in homosexual men.

To investigate the incidence of symptomatic primary human immunodeficiency virus type 1 (HIV-1) infection and its prognostic significance for HIV-1 disease progression, data for 328 homosexual men from four cohort studies were evaluated. Rates of diarrhea, fever, night sweats, cough, and fatigue prior to, during, and after seroconversion were compared by use of Poisson regression, and the prognostic significance of these symptoms was evaluated with survival methods. The incidence of all symptoms was elevated during seroconversion; however, only fever was associated with faster disease progression. Seven or more days of fever was reported by 13.8% of subjects; half of them developed AIDS within 6 years, whereas only one-fourth of the men without fever developed AIDS within 6 years. In addition, fever was the only symptom associated with shortened survival and increased CD4 cell loss. Persons experiencing prolonged periods of fever during seroconversion should therefore be considered for early treatment, including prophylaxis against opportunistic infections and combinations of antiretroviral drugs.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Serum levels of human immunodeficiency virus type 1 (HIV-1) RNA after seroconversion: a predictor of long-term mortality in HIV infection.

A cohort of 79 homosexual men with documented dates of human immunodeficiency virus type 1 (HIV-1) seroconversion and baseline CD4 cell counts of > or = 500/microL were followed for up to 11.5 years. HIV-1 RNA was measured from stored sera obtained a median of 7 months after the estimated seroconversion date. AIDS progression and mortality among the men were studied, stratified by median baseline levels of HIV-1 RNA. AIDS progression rates at 11.5 years were 69% and 34%, respectively, among those with higher versus lower than median baseline virus loads (> or = 3040 copies/mL; P = .002), and mortality rates were 61% and 27%, respectively (P = .003). Survival curves continued to diverge throughout the 11.5 years, suggesting that the future clinical course of HIV-1 infection may already be determined at the earliest phases of disease. Initiation of definitive treatment very early in HIV-1 infection may be essential.

Adult↗
PubMed1997

Modelling the impact of HIV disease on mortality in gay and bisexual men.

OBJECTIVE: To assess how HIV infection and AIDS (HIV/AIDS) impacts on mortality rates for gay and bisexual men. METHODS: Vital statistics data were obtained for a large Canadian urban centre from 1987 to 1992. Three scenarios were utilized with assumed proportions of gay and bisexual men of 3%, 6% and 9% among the male population age 20 years. For each scenario, non-HIV deaths were distributed according to the assumed proportion of the total population (3%, 6% or 9%) but 95% of HIV deaths were distributed to gay and bisexual men as this is the proportion of AIDS cases in gay and bisexual men in this centre. The main outcome measures of interest were age-specific patterns of death, life expectancy and life expectancy lost due to HIV/AIDS at exact age 20 years, and the probability of living from age 20 to 65 years. RESULTS: Estimates of the mid-period gay and bisexual population ranged from 5406 to 16,219 for the three scenarios, and total deaths in these men from 953 to 1703. Age-specific mortality was significantly higher for gay and bisexual men than all men aged 30-44. Life expectancy at age 20 for gay and bisexual men ranged from 34.0 years to 46.3 years for the 3% and 9% scenarios respectively. These were all lower than the 54.3 year life expectancy at age 20 for all men. The probability of living from age 20 to 65 years for gay and bisexual men ranged from 32% for the 3% scenario, to 59% for the 9% scenario. These figures were considerably lower than for all men where the probability of living from 20 to 65 was 78%. CONCLUSION: In a major Canadian centre, life expectancy at age 20 years for gay and bisexual men is 8 to 20 years less than for all men. If the same pattern of mortality were to continue, we estimate that nearly half of gay and bisexual men currently aged 20 years will not reach their 65th birthday. Under even the most liberal assumptions, gay and bisexual men in this urban centre are now experiencing a life expectancy similar to that experienced by all men in Canada in the year 1871.

Adult↗
PubMed1997

Needle exchange is not enough: lessons from the Vancouver injecting drug use study.

OBJECTIVE: To describe prevalence and incidence of HIV-1, hepatitis C virus (HCV) and risk behaviours in a prospective cohort of injecting drugs users (IDU). SETTING: Vancouver, which introduced a needle exchange programme (NEP) in 1988, and currently exchanges over 2 million needles per year. DESIGN: IDU who had injected illicit drugs within the previous month were recruited through street outreach. At baseline and semi-annually, subjects underwent serology for HIV-1 and HCV, and questionnaires on demographics, behaviours and NEP attendance were completed. Logistic regression analysis was used to identify determinants of HIV prevalence. RESULTS: Of 1006 IDU, 65% were men, and either white (65%) or Native (27%). Prevalence rates of HIV-1 and HCV were 23 and 88%, respectively. The majority (92%) had attended Vancouver's NEP, which was the most important syringe source for 78%. Identical proportions of known HIV-positive and HIV-negative IDU reported lending used syringes (40%). Of HIV-negative IDU, 39% borrowed used needles within the previous 6 months. Relative to HIV-negative IDU, HIV-positive IDU were more likely to frequently inject cocaine (72 versus 62%; P < 0.001). Independent predictors of HIV-positive serostatus were low education, unstable housing, commercial sex, borrowing needles, being an established IDU, injecting with others, and frequent NEP attendance. Based on 24 seroconversions among 257 follow-up visits, estimated HIV incidence was 18.6 per 100 person-years (95% confidence interval, 11.1-26.0). CONCLUSIONS: Despite having the largest NEP in North America, Vancouver has been experiencing an ongoing HIV epidemic. Whereas NEP are crucial for sterile syringe provision, they should be considered one component of a comprehensive programme including counselling, support and education.

Adolescent↗
PubMed1997

Determinants of HIV seroconversion in injection drug users during a period of rising prevalence in Vancouver.

To identify determinants of HIV seroconversion among injection drug users (IDUs) during a period of rising prevalence, a case-control investigation was conducted. Cases were IDUs with a new positive test after 1 January 1994, and a negative test within the prior 18 months. Controls required 2 negative tests during the same period. Subjects completed a questionnaire on demographic, psychosocial, and behavioural factors. Eighty-nine cases and 192 controls were similar with respect to gender, age, ethnicity and inter-test interval. Multivariate analyses of events during the inter-test interval showed borrowing syringes (adj. OR = 2.96; P < 0.006), unstable housing (adj. OR = 2.01; P = 0.03) and injecting > or = 4 times daily (adj. OR = 1.71; P = 0.06) to be independently associated with seroconversion. Protective associations were demonstrated for sex with opposite gender (adj. OR = 0.36; P = 0.001) and tetrahydrocannabinol use (adj. OR = 0.41; P = 0.001). There is a need to evaluate programmes dealing with addiction, housing and the social underpinnings of risk behaviours in this population.

Adult↗
PubMed1997

Social determinants predict needle-sharing behaviour among injection drug users in Vancouver, Canada.

Despite the fact that needle exchange was introduced in Vancouver as early as 1988, needle sharing remains common. An analysis was conducted to identify determinants of borrowing used needles among subjects participating in a case-control study. IDUs had a documented HIV seroconversion after 1 January, 1994 (n = 89), or repeatedly tested HIV-seronegative after this date (n = 192). Interviewer-administered questionnaires focused on drug use, sexual behaviours, source of needles and depression. Subjects were asked if they had "ever been forced to have sex" as a child, youth or adult. Logistic regression identified determinants of borrowing needles. After controlling for HIV serostatus, factors independently associated with borrowing were injecting > 4 times/day, polydrug use, and ever experiencing non-consensual sex (AOR = 3.4, 95% CI: 1.8, 6.5). Depression was associated with borrowing, although not independently so. Homosexual activity was independently associated with borrowing among males, whereas living with a sexual partner was an independent predictor for females. Access or barriers to clean needle use were not associated with borrowing. Social determinants, particularly a history of sexual abuse, are among the most significant predictors of needle borrowing among Vancouver's IDUs. Early identification of these factors should be a component of HIV prevention programmes.

Adult↗
PubMed1996

Lack of consistency between five definitions of nonprogression in cohorts of HIV-infected seroconverters.

OBJECTIVE: To identify appropriate criteria for characterizing HIV-infected nonprogressors. DESIGN: Five definitions were compared as follows: (1) last CD4 count > 500 x 10(6)/l; (2) two most recent CD4 counts > 500 x 10(6)/l; (3) calculated CD4 count based on linear regression > 500 x 10(6)/l; (4) CD4 slope > or = 0 with no antiretroviral use; (5) all CD4 counts > 500 x 10(6)/l, decline in CD4 slope < 5 cells per year, no antiretroviral use. PARTICIPANTS: Five prospective cohorts of homosexual men with documented dates of HIV-1 seroconversion. MAIN OUTCOME MEASURES: Proportions of nonprogressors were calculated 7, 8, 9 and 10 years following seroconversion (n = 285). Definitions were evaluated with respect to consistency over time and across sites. Subjects lacking CD4 counts within 3 years preceding end of follow-up were excluded. RESULTS: Across sites, proportions of nonprogressors ranged from 1% (definition 5) to 17.5% (definition 1) 10 years after seroconversion. Definitions based on absolute CD4 counts (definitions 1-3) had higher proportions and were less consistent than those based on stable slopes (definitions 4 and 5). For each definition, proportions decreased as follow-up increased, but were most stable for definition 4 (3%). Site differences decreased as follow-up increased, but remained nearly threefold for definitions 1-3. None of the definitions classified the same subjects as nonprogressors at any timepoint. CONCLUSIONS: Observations regarding nonprogression are highly dependent on the definition and the duration of follow-up. Our findings highlight methodological challenges which will need to be overcome in natural history studies of nonprogression.

CD4-Positive T-Lymphocytes↗
PubMed1996

A decade of research on the natural history of HIV infection: Part 1. Markers.

Within the context of HIV disease, a marker may be described as a consequence of disease that varies over time but does not necessarily predict future disease course. To date, the most powerful marker of HIV disease progression is the CD4 cell count. Other immunologic markers include neopterin, beta 2-microglobulin, and total and HIV-specific immunoglobulin levels. Further research, which focuses on cell-mediated factors such as interleukins, tumour necrosis factor, natural killer cell activity and apoptosis, is required. Measures of viral burden, such as p24 antigenemia and proviral DNA or RNA, may also offer additional prognostic information. As methods involving quantitative polymerase chain reaction become more refined, it is hoped that they may soon be applied to the clinical setting. Clinical markers of interest include the appearance of minor opportunistic infections and the occurrence of acute retroviral syndrome, which may indicate a faster disease course. Although population-based studies have identified a number of HIV disease markers, further research is required to generalize these findings to the individual level.

AIDS-Related Opportunistic Infections↗
PubMed1996

A decade of research on the natural history of HIV infection: Part 2. Cofactors.

Cofactors of HIV disease may be considered risk modifiers that are causally related to future disease course. The search for potential cofactors, of viral, host or environmental origin, may provide avenues for altering the natural history of HIV infection. Potential viral cofactors include viral strains, such as syncytium-inducing and nonsyncytium-inducing variants, and strains that are resistant to specific antiretroviral therapies. Although there is strong evidence that sexually transmitted diseases that lead to genital ulcers or abrasions are important cofactors of HIV transmission, their role as cofactors in HIV disease progression is less clear. Further study of agents such as human herpesviruses 6 and 8 and hepatitis C may shed light on the role of other infectious agents in progressive HIV disease. Far less research has been conducted on behavioural, genetic and sociodemographic factors that may influence HIV disease progression rates. Since current anti-HIV therapies do not offer a cure, but only a means of prolonging life, the identification of possible cofactors is critical.

Comorbidity↗