Biomedical subjects

David W Purcell

Publications and source records attributed to David W Purcell.

35 records · Page 2Linked to original sources

PubMed2005

Sexual risk, substance use, and psychological distress in HIV-positive gay and bisexual men who also inject drugs.

OBJECTIVES: Gay and bisexual men and injection drug users (IDU) are the two main groups at risk of HIV exposure in the United States, but few studies have focused on the intersection of these two groups. Little is known about HIV-positive gay and bisexual IDU. The aim of this study is to identify and compare differences in HIV transmission risk behaviors and psychological distress in HIV-positive gay and bisexual men by injection versus non-injection drug use. METHODS: Data were from the baseline assessment of a randomized controlled trial of an HIV prevention intervention for HIV-positive gay and bisexual men. RESULTS: Of the 1168 men, 236 (20%) reported injection drug use, 500 (43%) reported only non-injection drug use, and 422 (36%) reported no drug use. More of the IDU reported having sex with women, and identified themselves as "barebackers" (i.e. men who intentionally have unprotected anal intercourse). IDU reported more unprotected sexual behaviors than men who did not use drugs, but their sexual risk behaviors were similar to those of men who used non-injection drugs. IDU, compared with other drug users, reported more use of non-injected methamphetamine, amphetamine, barbiturates, and gamma hydroxybutyrate. More IDU, compared with the other two groups, reported sexual abuse, anxiety, and hostility. CONCLUSION: HIV-positive gay and bisexual IDU are a distinct group from other HIV-positive gay and bisexual men. Prevention case management and interventions that help men cope with multiple health concerns and prevent HIV transmission are needed for this population.

Adolescent↗

PubMed2005

Predictors of the use of viagra, testosterone, and antidepressants among HIV-seropositive gay and bisexual men.

OBJECTIVE: To examine the use and correlates of the use of prescription drugs that may affect sexual behavior among HIV-positive gay and bisexual men. METHODS: In a cross-sectional assessment of baseline data from a behavioral intervention, we recruited 1168 HIV-positive gay and bisexual men in 2000-2001 from community venues in New York City and San Francisco, and determined the point prevalence of the use of viagra, testosterone, and antidepressants. We examined bivariate and multivariate associations between the use of each drug and demographics, health status, substance use, psychological symptoms, and sexual risk. RESULTS: The current use of antidepressants was 21%, testosterone 19%, and viagra 12%. Some viagra users reported using drugs that could interact dangerously with viagra. The use of viagra, testosterone, or antidepressants was related to unprotected receptive anal intercourse and unprotected insertive oral intercourse (UIOI) with both HIV-positive and HIV-negative/unknown-status casual partners. The use of viagra was also associated with unprotected insertive anal intercourse. In multivariate models, viagra use was associated with being older, more educated, using ketamine, and engaging in UIOI with HIV-negative/unknown-status casual partners. Testosterone use was associated with being more educated and using nitrites (poppers). Antidepressant use was associated with race, using poppers, and being more depressed. CONCLUSION: Prescription medications used by HIV-positive men can have unintended negative effects such as drug interactions or associations with risky sexual behavior, particularly a drug such as viagra that is fast acting, short lasting, and provides a desirable effect. Physicians should discuss these issues with patients when prescribing, and interventions should address these challenges.

Adult↗

PubMed2005

What happened in the SUMIT trial? Mediation and behavior change.

OBJECTIVES: We wished to identify which potential mediators of the Seropositive Urban Men's Intervention Trial (SUMIT) intervention were in fact changed by the intervention, and further to identify which among these factors distinguished men who decreased their risk behavior relative to those who increased it, irrespective of the intervention arm. METHODS: We examined social cognitive theory and other psychosocial variables that the intervention was designed to affect (potential mediators) in both sets of analyses. These were assessed at baseline, 3-month follow-up, and 6-month follow-up. We tested which potential mediators were changed by the intervention relative to the comparison arm, and which of these factors distinguished men discontinuing risk behavior [unprotected insertive anal intercourse (UIAI) or UIAI with HIV-negative or status-unknown partners] compared with those initiating it. RESULTS: Factors changed by the intervention included partner serostatus assumption making, hedonistic condom outcome expectancies, anxiety and depression. Factors associated with behavioral risk reduction included personal responsibility to protect others from infection and self-evaluative outcome expectancies regarding transmission risk behavior. These constructs are similar and involve the engagement of moral processes and altruism in sexual behavior with others. DISCUSSION: The present results suggest that, although we designed the intervention to enhance personal responsibility to protect others from HIV, we were not successful in this goal. However, changes in this factor did prove to be an important correlate of behavior change. Possible ways to design and deliver more successful interventions are discussed.

Attitude to Health↗

PubMed2004

Interventions for seropositive injectors-research and evaluation: an integrated behavioral intervention with HIV-positive injection drug users to address medical care, adherence, and risk reduction.

BACKGROUND: Behavioral interventions to address the complex medical and HIV risk reduction needs of HIV-seropositive (HIV-positive) injection drug users (IDUs) are urgently needed. We describe the development of Interventions for Seropositive Injectors-Research and Evaluation (INSPIRE), a randomized controlled trial of an integrated intervention for HIV-positive IDUs, and the characteristics of the baseline sample. METHODS: HIV-positive IDUs were recruited from community settings in 4 US cities. After completing a baseline assessment, participants who attended the first session were randomly assigned to (1) a 10-session peer mentoring intervention designed to improve utilization of HIV care, to improve adherence to HIV medications, and to reduce sexual and injection risk or (2) an 8-session videotape control. Periodic follow-up for 12 months is ongoing. RESULTS: A total of 1161 HIV-positive IDUs completed the baseline assessment, and 966 (83%) were randomized. Retention rates are greater than 80% for all follow-up periods. Approximately 79% of baseline participants reported a recent medical visit, 49% were taking highly active antiretroviral therapy, and 19% had an undetectable viral load. Use of injection and noninjection substances was prevalent, and sexual and injection risks were each reported by more than 25% of participants. CONCLUSION: There is a need for an integrated intervention for HIV-positive IDUs, and these data show the acceptability of such an approach.

Educational Status↗

PubMed2004

Sexual risk of HIV transmission is missed by traditional methods of data collection.

Brief acts of unprotected anal sex (i.e.'dipping') have not been systematically measured in AIDS research. Eleven per cent of HIV-positive men who reported that they had not engaged in any unprotected insertive anal intercourse with an HIV-negative or unknown status partner reported that they did engage in insertive 'dipping'. Men reported 'dipping' an average of 5.1 times, representing 773 acts of insertive intercourse that would have been missed by traditional methods of sexual data behavior.

Condoms↗

PubMed2004

HIV serostatus disclosure to sexual partners among HIV-positive injection drug users.

Utilizing mixed methods analyses with cross-sectional data from an ethnically diverse sample of HIV-seropositive injection drug users (IDUs), we sought to examine disclosure and sexual behavior based on partner type, partner serostatus, and transmission risk. Results indicated that more participants disclosed to their HIV-positive sex partners than to their HIV-negative or unknown status sex partners. However, unexpectedly, we found that more participants disclosed to casual sex partners than primary partners before first sexual contact. Consistent disclosers reported more unprotected sexual activity compared to nondisclosers, and were more likely to believe they had a responsibility to disclose. Nondisclosers were less likely than consistent disclosers to believe it was important to protect sex partners from HIV and were more resentful of wearing condoms. In terms of the qualitative data, we found that the emotionally upsetting narratives came from those we defined as "eventual disclosers." This category represented those participants who were in relationships and had not disclosed their status to their primary partners until after having had sex with that partner. These narratives indicated that researchers looking at disclosure behavior should be aware of varying disclosure contexts as well as the emotional consequences impacting disclosure decision-making within these contexts.

Adult↗

PubMed2004

Race/ethnic disparities in HIV testing and knowledge about treatment for HIV/AIDS: United States, 2001.

In the United States, access to HIV care has remained suboptimal for people of color. To assess racial disparities in HIV testing and knowledge about treatment for HIV/AIDS in the United States, we analyzed the 2001 Behavioral Risk Factor Surveillance System. We obtained the percentage of respondents aged 18 to 64 years who: (1) were tested for HIV ever and recently (in the past 12 months) excluding for blood donations and (2) responded "true" to the statement, "There are medical treatments available that are intended to help a person who is infected with HIV to live longer." We calculated the difference in rates of HIV testing and knowledge about treatment between blacks or Latinos compared to whites. Overall, of the 162,962 respondents, 44.7% had been tested for HIV and 12.8% were tested in the past year. Overall, 86.4% answered "true" to the statement on treatment for HIV/AIDS. HIV testing rates were significantly lower among whites (ever, 42.4%; recent, 10.8%) than blacks (ever, 59.7%; recent, 23.4%) or Latinos (ever 45.6%, recent 14.8%). Compared to knowledge among whites (89.6%), knowledge level was, lower among blacks (odds ratio [OR] = 0.58, 95% confidence interval [CI] = 0.52, 0.64) and Latinos (OR = 0.67, 95%CI = 0.59, 0.75) even after adjusting for sociodemographics and HIV testing status. The knowledge gap among blacks compared to whites decreased with increasing income and education. We conclude that knowledge about the availability of antiretroviral treatment was high overall. Compared to whites, blacks, and latinos had significantly higher HIV testing rates but significantly lower knowledge about antiretrovirals.

AIDS Serodiagnosis↗

PubMed2004

Human temporal auditory acuity as assessed by envelope following responses.

Temporal auditory acuity, the ability to discriminate rapid changes in the envelope of a sound, is essential for speech comprehension. Human envelope following responses (EFRs) recorded from scalp electrodes were evaluated as an objective measurement of temporal processing in the auditory nervous system. The temporal auditory acuity of older and younger participants was measured behaviorally using both gap and modulation detection tasks. These findings were then related to EFRs evoked by white noise that was amplitude modulated (25% modulation depth) with a sweep of modulation frequencies from 20 to 600 Hz. The frequency at which the EFR was no longer detectable was significantly correlated with behavioral measurements of gap detection (r = -0.43), and with the maximum perceptible modulation frequency (r = 0.72). The EFR techniques investigated here might be developed into a clinically useful objective estimate of temporal auditory acuity for subjects who cannot provide reliable behavioral responses.

Acoustic Stimulation↗

PubMed2004

Positive and negative consequences of HIV disclosure among seropositive injection drug users.

This study examines HIV status disclosure in an ethnically diverse sample of HIV-seropositive injection drug users (IDUs) from New York City and San Francisco. Qualitative interviews were conducted with 158 participants. Analyses revealed a number of negative and positive consequences of disclosing serostatus to sexual partners. Negative consequences included stigma, rejection by sexual partners and others, loss of intimacy, and threats to personal well-being. Positive rewards resulting from disclosure included increased social support and intimacy with partners, reaffirmation of one's sense of self, and the opportunity to share personal experiences and feelings with sexual partners. The role of responsibility in impacting disclosure and nondisclosure revealed varied patterns in terms of how this construct impacts disclosure and resulting behaviors with sexual partners. Some participants used particular strategies, such as getting involved in seroconcordant relationships or minimizing intimacy in relationships, in order to combat potential negative outcomes of disclosure. For others, positive rewards were viewed as important enough to risk negative consequences. Interventions for HIV-positive IDUs are discussed.

Adult↗

PubMed2003

Concurrent measurement of distortion product otoacoustic emissions and auditory steady state evoked potentials.

Distortion product otoacoustic emissions (DPOAEs) and auditory steady state evoked response potentials (ASSRs) can both be evoked by tone pairs with frequencies f(1) and f(2). The DPOAE is maximal at 2f(1)-f(2) and the ASSR is maximal at f(2)-f(1). Since DPOAE magnitude depends on the ratio f(2)/f(1), but ASSR amplitude depends on the beat frequency f(2)-f(1), compromises are necessary when recording both responses concurrently. Tone pairs with f(2) of 900, 1800 and 3600 Hz were presented simultaneously at either 40 or 50 dB sound pressure level (SPL). The f(1) frequency of each pair was approximately 85 or 180 Hz lower than f(2). Phase measurements were used to calculate apparent latencies at 40 dB SPL. For increasing f(2), DPOAE latencies were 14.5, 9.7 and 6.3 ms for 85 Hz beats, and 11.5, 9.0 and 4.3 ms for 180 Hz beats. ASSR latencies were 22.0, 15.7 and 17.8 ms at 85 Hz, and 17.7, 11.3 and 9.6 ms at 180 Hz. From a model of the mechanical transmission in the cochlea, delays between the basilar membrane and the generator of the ASSR were estimated as 15.4, 12.2 and 15.3 ms at 85 Hz and 8.6, 7.6 and 8.0 ms at 180 Hz.

Acoustic Stimulation↗

PubMed2003

Sexual behavior among HIV-positive men who have sex with men: what's in a label?

Relatively little attention has been paid to the use and importance of labels used by men who have sex with men to describe insertive or receptive sexual behavior during intercourse. This study examines sexual self-labels, sexual behavior, HIV transmission risk, and psychological functioning among 205 HIV-seropositive men who have sex with men. The majority of participants (88%) identified as a top, a bottom, or versatile. Tops were more likely to engage in insertive anal intercourse than bottoms, and bottoms were more likely to engage in receptive anal intercourse than tops, with versatiles reporting intermediate rates of both behaviors. Although the results suggest preliminary evidence regarding the predictive utility of self-labels, sexual behaviors of self-label groups were greatly overlapping. Differences were found among self-label groups in gay self-identification, internalized homophobia, sexual sensation seeking, and anxiety. Results suggest an added value in assessing self-labels in addition to asking about sexual behavior.

Demography↗

PubMed2003

Estimating bone conduction transfer functions using otoacoustic emissions.

A technique for estimating the nonparametric bone conduction transfer function using distortion product otoacoustic emissions (DPOAEs) is presented. Individual transfer functions were obtained using DPOAEs recorded from a single ear of five normal-hearing adults. Repeatability of the technique was investigated by performing measurements on at least three dates. Functions were reasonably repeatable, and were unique to each individual as expected from subjective measurements. Input force and DPOAE measurements were made for each individual, and a model of the auditory periphery representative of an average person was employed. The technique is objective and requires only passive cooperation, but robust DPOAEs are needed and the measurement time can be onerous for a wide frequency band or fine frequency resolution. With appropriate adjustments to the model of the auditory periphery, the method could be applied with animal models.

Acoustics↗

PubMed2003

Human auditory steady-state responses: the effects of recording technique and state of arousal.

UNLABELLED: There is some controversy in the literature about whether auditory steady-state responses (ASSRs) can be reliably recorded in all subjects and whether these responses consistently decrease in amplitude during drowsiness. In 10 subjects, 40-Hz ASSRs became significantly different from background electroencephalogram activity with a probability of P < 0.01 and an average time of 22 s (range, 2-92 s), provided that the responses were analyzed with time-domain averaging rather than spectral averaging. In a second experiment with 10 subjects, 40-Hz ASSRs recorded between the vertex and posterior neck consistently decreased in amplitude during drowsiness and sleep. Findings that the ASSR may occasionally increase during drowsiness may be explained by postauricular muscle responses recorded from a mastoid reference. These may occur during drowsiness in association with rolling-eye movements. ASSRs recorded between the vertex and posterior neck are not distorted by these reflexes. These findings combine with previous literature on the effects of general anesthetics on the ASSR to confirm that the ASSR is a valid option for monitoring the hypnotic effects of general anesthetics. IMPLICATIONS: Auditory steady-state responses to stimuli presented at rates near 40 Hz can be used to monitor anesthesia. These responses can be quickly and reliably recorded during both sleep and wakefulness, provided that appropriate averaging techniques are used.

Acoustic Stimulation↗

PubMed2002

Estimating the audiogram using multiple auditory steady-state responses.

Multiple auditory steady-state responses were evoked by eight tonal stimuli (four per ear), with each stimulus simultaneously modulated in both amplitude and frequency. The modulation frequencies varied from 80 to 95 Hz and the carrier frequencies were 500, 1000, 2000, and 4000 Hz. For air conduction, the differences between physiologic thresholds for these mixed-modulation (MM) stimuli and behavioral thresholds for pure tones in 31 adult subjects with a sensorineural hearing impairment and 14 adult subjects with normal hearing were 14+/-11, 5+/-9, 5+/-9, and 9+/-10 dB (correlation coefficients .85, .94, .95, and .95) for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. Similar results were obtained in subjects with simulated conductive hearing losses. Responses to stimuli presented through a forehead bone conductor showed physiologic-behavioral threshold differences of 22+/-8, 14+/-5, 5+/-8, and 5+/-10 dB for the 500-, 1000-, 2000-, and 4000-Hz carrier frequencies, respectively. These responses were attenuated by white noise presented concurrently through the bone conductor.

Adult↗

PubMed2002

Advantages and caveats when recording steady-state responses to multiple simultaneous stimuli.

This article considers the efficiency of evoked potential audiometry using steady-state responses evoked by multiple simultaneous stimuli with carrier frequencies at 500, 1000, 2000, and 4000 Hz. The general principles of signal-to-noise enhancement through averaging provide a basis for determining the time required to estimate thresholds. The advantage of the multiple-stimulus technique over a single-stimulus approach is less than the ratio of the number of stimuli presented. When testing two ears simultaneously, the advantage is typically that the multiple-stimulus technique is two to three times faster. One factor that increases the time of the multiple-response recording is the relatively small size of responses at 500 and 4000 Hz. Increasing the intensities of the 500- and 4000-Hz stimuli by 10 or 20 dB can enhance their responses without significantly changing the other responses. Using multiple simultaneous stimuli causes small changes in the responses compared with when the responses are evoked by single stimuli. The clearest of these interactions is the attenuation of the responses to low-frequency stimuli in the presence of higher-frequency stimuli. Although these interactions are interesting physiologically, their small size means that they do not lessen the advantages of the multiple-stimulus approach.

Audiometry, Pure-Tone↗

PubMedDate not supplied

Economic evaluation of an HIV prevention intervention for seropositive injection drug users.

OBJECTIVE: To assess the cost-effectiveness of Intervention for HIV-Seropositive injection drug users--Research and Evaluation (INSPIRE), designed to reduce risky sexual and needle-sharing behaviors in research sites in four US cities (2001-2003). METHODS: We collected data on program and participant costs. We used a mathematical model to estimate the number of sex partners of injection drug users expected to become infected with human immunodeficiency virus (HIV) (with and without intervention), cost of treatment for sex partners who became infected, and the effect of infection on partners' quality-adjusted life expectancy. We determined the minimum effect that INSPIRE must have on condom use among participants for the intervention to be cost-saving (intervention cost less than savings from averted HIV infections) or cost-effective (net cost per quality-adjusted life year saved less than $50,000). RESULTS: The intervention cost was $870 per participant. It would be cost-saving if it led to 53 percent reduction in the proportion of participants who had any unprotected sex in 1 year and cost-effective with 17 percent reduction. If behavior change lasted 3 months, the cost-effectiveness threshold was 66 percent; if 3 years, the threshold was 6 percent. CONCLUSIONS: Although cost-saving thresholds may not be achievable by the intervention, we anticipate that cost-effectiveness thresholds will be attained.

Cohort Studies↗

PubMedDate not supplied

CDC consultation on methamphetamine use and sexual risk behavior for HIV/STD infection: summary and suggestions.

In January 2005, the U.S. Centers for Disease Control and Prevention hosted a national consultation of scientists, public health officials, and community service providers to address growing concerns about the association of methamphetamine use and sexual risk behavior for HIV/STD infection, which is well documented among men who have sex with men. The purpose of the consultation was to review a representation of the current state of the science and practice on the topic in order to reduce the situational link of methamphetamine use and sexual risk. A set of suggestions for future research and programs were developed by the participants. This article provides a summary of content and recommendations from the consultation, and not an exhaustive review of the literature.

Centers for Disease Control and Prevention, U.S.↗