Showing papers by "David M. Boore published in 2023"
TL;DR: In this article , it was shown that the difference between FR and SRI amplifications for gradient profiles is due to the ratio of seismic impedances, whereas the latter is based on the square root of the seismic impedance ratios.
Abstract:
Amplifications of seismic waves traveling upward through a continuous, interface-free velocity profile are consistently smaller when computed using the square-root-impedance (SRI) method than when computed using full-resonance (FR) calculations. This was found for a wide range of velocity profiles. For realistic profiles, for which the gradient of velocity decreases with depth, the differences are not large, with the ratio of FR/SRI amplifications ranging from about 1.05 to 1.3. Comparisons of the amplifications from a continuous velocity profile with those from approximations to that profile using a stack of constant-velocity layers give some support to the hypothesis that the difference between FR and SRI amplifications for gradient profiles is because the former is controlled by the ratio of seismic impedances, whereas the latter is based on the square root of the seismic impedance ratios. This implies that gradient profiles will always have FR amplifications greater than SRI amplifications. A model-independent, easy-to-implement modification of the SRI amplifications is proposed that shows promise in bringing the SRI amplifications closer to the FR amplifications.
TL;DR: In this article , the authors found that feelings of loneliness did not predict sexual risk-taking within the first year of the COVID-19 pandemic, but loneliness did predict greater sexual risk taking 6 months later.
Abstract: In March 2020, in response to the COVID-19 pandemic, Canadian provincial governments instituted a variety of public health measures that included social distancing and isolation, which may have had unintended consequeses. According to the Loneliness and Sexual Risk Model, gay, bisexual, and other men who have sex with men (GBM) often cope with loneliness through risky sexual behaviors. Previous studies have demonstrated that COVID-19 measures such as social distancing and isolation led to increases in loneliness; thus, these measures may also have led to elevated sexual risk-taking among some GBM. Participants were recruited from an ongoing cohort study on GBM health and well-being, and were included in the current analysis if they had completed relevant study questions (n = 1134). GBM who reported lower levels of social support pre-COVID-19, were younger, and lived alone each reported greater loneliness during the first year of COVID-19. Although feelings of loneliness did not predict sexual risk-taking within the first year of COVID-19, loneliness did predict greater sexual risk-taking 6 months later. Additionally, younger GBM and those living alone were more likely to engage in sexual risk-taking at both COVID-19 data collection points. These findings offer some support of the Loneliness and Sexual Risk Model; however, it is possible that the unique circumstances of the COVID-19 pandemic resulted in a temporary suspension of this association, as many GBM took steps to protect themselves and partners in the context of COVID-19.
TL;DR: In this article , the authors explored factors associated with improvements in mental health symptoms among gbMSM with abnormal depression and anxiety scores over a period of four years, in Vancouver, Canada.
TL;DR: In this article , the authors compared 12-month incidence and persistence of anal HPV infection between vaccinated and unvaccinated men who have sex with men (GBM) in Montreal, Toronto, and Vancouver, Canada, from 2017 to 2019.
Abstract: Abstract Background Real-world evidence of human papillomavirus (HPV) vaccine effectiveness (VE) against longitudinal outcomes is lacking among gay, bisexual, and other men who have sex with men (GBM). We compared 12-month incidence and persistence of anal HPV infection between vaccinated and unvaccinated GBM. Methods We recruited GBM aged 16–30 years in Montreal, Toronto, and Vancouver, Canada, from 2017 to 2019. Participants were followed over a median of 12 months (interquartile range, 12–13 months). Participants self-reported HPV vaccination and self-collected anal specimens for HPV DNA testing. We calculated prevalence ratios (PR) for 12-month cumulative incidence and persistence with ≥1 quadrivalent vaccine type (HPV 6/11/16/18) between vaccinated (≥1 dose at baseline) and unvaccinated participants using a propensity score-weighted, modified Poisson regression. Results Among 248 participants, 109 (44.0%) were vaccinated at baseline, of whom 62.6% received 3 doses. PRs for HPV 6/11/16/18 were 0.56 (95% confidence interval [CI], .24–1.31) for cumulative incidence and 0.53 (95% CI, .25–1.14) for persistence. PRs were 0.23 (95% CI, .05–1.03) and 0.08 (95% CI, .01–.59) for incidence and persistence, respectively, among participants who received their first dose at age ≤23 years and 0.15 (95% CI, .03–.68) and 0.12 (95% CI, .03–.54) among participants who were sexually active for ≤5 years before vaccination. Conclusions Findings support national recommendations for HPV vaccination at younger ages or soon after sexual debut.
TL;DR: In this article , a focus group with residents from a low-income urban neighbourhood (downtown Vancouver, Canada) to assess recent healthcare experiences and elicit interest in mobile phone-based healthcare engagement for underserved residents was held.
Abstract: Mobile phone-based engagement approaches provide potential platforms for improving access to primary healthcare (PHC) services for underserved populations. We held two focus groups (February 2020) with residents (n = 25) from a low-income urban neighbourhood (downtown Vancouver, Canada), to assess recent healthcare experiences and elicit interest in mobile phone-based healthcare engagement for underserved residents. Note-based analysis, guided by interpretative description, was used to explore emerging themes. Engagement in PHC was complicated by multiple, intersecting personal-level and socio-structural factors, and experiences of stigma and discrimination from care providers. Perceived inadequacy of PHC services and pervasive discrimination reported by participants indicate a significant and ongoing need to improve client-provider relationships to address unmet health needs. Mobile phone-based engagement was endorsed, highlighting phone ownership and client-provider text-messaging, facilitated by non-clinical staff such as peers, as helpful to strengthening retention and facilitating care team connection. Concerns raised included reliability, cost, and technology and language accessibility.
TL;DR: This article measured the effect of nondifferential exposure misclassification associated with self-reported vaccination on vaccine effectiveness (VE) estimates and conducted a multidimensional and probabilistic quantitative bias analysis to correct VE estimates.
Abstract: Background: Self-report of human papillomavirus (HPV) vaccination has ~80–90% sensitivity and ~75–85% specificity. We measured the effect of nondifferential exposure misclassification associated with self-reported vaccination on vaccine effectiveness (VE) estimates. Methods: Between 2017–2019, we recruited sexually active gay, bisexual, and other men who have sex with men aged 16–30 years in Canada. VE was derived as 1−prevalence ratio × 100% for prevalent anal HPV infection comparing vaccinated (≥1 dose) to unvaccinated men using a multivariable modified Poisson regression. We conducted a multidimensional and probabilistic quantitative bias analysis to correct VE estimates. Results: Bias-corrected VE estimates were relatively stable across sensitivity values but differed from the uncorrected estimate at lower values of specificity. The median adjusted VE was 27% (2.5–97.5th simulation interval = −5–49%) in the uncorrected analysis, increasing to 39% (2.5–97.5th simulation interval = 2–65%) in the bias-corrected analysis. Conclusion: A large proportion of participants erroneously reporting HPV vaccination would be required to meaningfully change VE estimates.
TL;DR: In 2018, the pre-exposure prophylaxis (PrEP) program was initiated in British Columbia (BC), Canada, providing PrEP at no cost to qualifying residents as discussed by the authors .
Abstract: In 2018, the pre-exposure prophylaxis (PrEP) program was initiated in British Columbia (BC), Canada, providing PrEP at no cost to qualifying residents. This observational study discussed the steps to develop key evidence-based monitoring indicators and their calculation using real-time data. The indicators were conceptualized, developed, assessed and approved by the Technical Monitoring Committee of representatives from five health authority regions in BC, the BC Ministry of Health, the BC Centre for Disease Control, and the BC Centre for Excellence in HIV/AIDS. Indicator development followed the steps adopted from the United States Centers for Disease Control and Prevention framework for program evaluation in public health. The assessment involved eight selection criteria: data quality, indicator validity, existing scientific evidence, indicator informativeness, indicator computing feasibility, clients’ confidentiality maintenance capacity, indicator accuracy, and administrative considerations. Clients’ data from the provincial-wide PrEP program (January 2018—December 2020) shows the indicators’ calculation. The finalized 14 indicators included gender, age, health authority, new clients enrolled by provider type and by the health authority, new clients dispensed PrEP, clients per provider, key qualifying HIV risk factor(s), client status, PrEP usage type, PrEP quantity dispensed, syphilis and HIV testing and incident cases, and adverse drug reaction events. Cumulative clients’ data (n = 6966; 99% cis-gender males) identified an increased new client enrollment and an unexpected drop during the COVID-19 pandemic. About 80% dispensed PrEP from the Vancouver Coastal health authority. The HIV incidence risk index for men who have sex with men score ≥10 was the most common qualifying risk factor. The framework we developed integrating indicators was applied to monitor our PrEP program, which could help reduce the public health impact of HIV.
TL;DR: The Engage Study as discussed by the authors is a longitudinal biobehavioral cohort study of gay, bisexual and other men who have sex with men (GBM) in Toronto, Montreal, and Vancouver.
Abstract: The Engage Study is a longitudinal biobehavioral cohort study of gay, bisexual and other men who have sex with men (GBM) in Toronto, Montreal, and Vancouver. Baseline data (2,449 participants) were collected from February 2017 - August 2019 using respondent-driven sampling (RDS). Recruitment in Montreal required fewer seeds, had a much shorter recruitment period, and recruited the largest sample.To better understand why RDS recruitment was more successful in Montreal compared to other sites, we conducted an analysis to examine RDS recruitment characteristics for GBM in each of the three study sites, explore demographic characteristics and measures of homophily, that is, the tendency of individuals to recruit other study participants who are like themselves, and compared motivations for study participation.Montreal had the greatest proportion of participants over the age of 45 (29.1% in Montreal, 24.6% in Vancouver, and 21.0% in Toronto) and the highest homophily for this age group, but homophily was high across the three cities. Montreal also reported the lowest percentage of participants with an annual income greater or equal to $60,000 (7.9% in Montreal, 13.1% in Vancouver and 10.6% in Toronto), but homophily was similar across all three cities. The majority of participants indicated interest in sexual health and HIV as the main reason for participating (36.1% in Montreal, 34.7% in Vancouver, and 29.8% in Toronto). Financial interest as the main reason for participation was low (12.7% in Montreal, 10.6% in Vancouver, and 5.7% in Toronto).Taken together, although we found some differences in study demographic characteristics and homophily scores, we were unable to fully explain the different recruitment success based on the data available. Our study underlines the fact that success of RDS implementation may vary by unknown factors, and that researchers should be proactive and flexible to account for variability.