Displaying publications 1 - 20 of 35 in total

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  1. Martin TE
    Science, 2015 Aug 28;349(6251):966-70.
    PMID: 26315435 DOI: 10.1126/science.aad1173
    Life history theory attempts to explain why species differ in offspring number and quality, growth rate, and parental effort. I show that unappreciated interactions of these traits in response to age-related mortality risk challenge traditional perspectives and explain life history evolution in songbirds. Counter to a long-standing paradigm, tropical songbirds grow at similar overall rates to temperate species but grow wings relatively faster. These growth tactics are favored by predation risk, both in and after leaving the nest, and are facilitated by greater provisioning of individual offspring by parents. Increased provisioning of individual offspring depends on partitioning effort among fewer young because of constraints on effort from adult and nest mortality. These growth and provisioning responses to mortality risk finally explain the conundrum of small clutch sizes of tropical birds.
  2. Martin TE, Ton R, Niklison A
    Ecol Lett, 2013 Jun;16(6):738-45.
    PMID: 23473270 DOI: 10.1111/ele.12103
    Intrinsic processes are assumed to underlie life history expression and trade-offs, but extrinsic inputs are theorised to shift trait expression and mask trade-offs within species. Here, we explore application of this theory across species. We do this based on parentally induced embryo temperature as an extrinsic input, and mass-specific embryo metabolism as an intrinsic process, underlying embryonic development rate. We found that embryonic metabolism followed intrinsic allometry rules among 49 songbird species from temperate and tropical sites. Extrinsic inputs via parentally induced temperatures explained the majority of variation in development rates and masked a relationship with metabolism; metabolism explained a minor proportion of the variation in development rates among species, and only after accounting for temperature effects. We discuss evidence that temperature further obscures the expected interspecific trade-off between development rate and offspring quality. These results demonstrate the importance of considering extrinsic inputs to trait expression and trade-offs across species.
  3. Surendran S, Thomas E
    Am J Orthod Dentofacial Orthop, 2014 Jan;145(1):7-14.
    PMID: 24373650 DOI: 10.1016/j.ajodo.2013.09.007
    The objective of this study was to determine whether dental calcification can be used as a first-level diagnostic tool for assessment of skeletal maturity.
  4. Lim SH, Guadamuz TE, Wei C, Chan R, Koe S
    AIDS Behav, 2012 Oct;16(7):1979-87.
    PMID: 22714116
    We examined socio-demographic and behavioral characteristics of men who have sex with men (MSM) residing in Asia and correlates of unprotected receptive intercourse with Internet ejaculation (URAIE). Asia Internet MSM Sex Survey, a behavioral survey of MSM in Asia was conducted from 1 January to 28 February 2010. Data analysis was limited to participants aged 18 or above, biological male, and had one regular or casual sex partner in the past 6 months (n = 10,413). Pearson's Chi-square test, t test and logistic regression were used to examine the correlates of URAIE in the past 6 months, the highest risk sexual behavior sampled. Of 7311 participants who had receptive anal intercourse, 47.5 % had URAIE, which was associated with the following attributes: less than high-school education and pre-college education compared to university (AOR = 1.53, 95 % CI: 1.28, 1.83; AOR = 1.22, CI: 1.08, 1.37), being in the heterosexual marriage (AOR = 1.35, CI: 1.18, 1.56), having regular partners or both regular and casual partners compared to having casual partners (AOR = 2.85, CI: 2.48, 3.27; AOR = 2.32, CI: 2.06, 2.62), HIV-positive compared to HIV-negative status (AOR = 1.39, 95 % CI: 1.08, 1.81), higher perception of HIV risk (AOR = 1.62, CI: 1.34, 1.95), use of recreational drug before sex (AOR = 1.30, CI: 1.14, 1.49), and use of the Internet as the main way to seek sex partners (AOR = 1.21, CI: 1.08, 1.36). MSM from certain Asian countries reported alarming rates of URAIE. The internet can be used as a platform for HIV surveillance and intervention.
  5. Yang C, Guadamuz TE, Lim SH, Koe S, Wei C
    LGBT Health, 2016 Apr;3(2):168-74.
    PMID: 26789393 DOI: 10.1089/lgbt.2014.0041
    We explored factors associated with alcohol use before or during sex among a sample of 10,861 men who have sex with men (MSM) in Asia who were recruited online for the study. Multinomial logistic regression analysis indicated that having sex under the influence of alcohol was associated with having multiple male partners, seeking partners primarily through gay bar/gym/dance party/friends, selling sex and using multiple drugs during the past 6 months, and unprotected anal sex. More efforts are needed to better assess alcohol use and misuse among MSM in Asia and understand contextual influences on alcohol use and HIV-related behaviors in order to implement culturally-specific interventions.
  6. Mitchell AE, Boersma J, Anthony A, Kitayama K, Martin TE
    Am Nat, 2020 10;196(4):E110-E118.
    PMID: 32970467 DOI: 10.1086/710151
    AbstractOrganisms living at high elevations generally grow and develop more slowly than those at lower elevations. Slow montane ontogeny is thought to be an evolved adaptation to harsh environments that improves juvenile quality via physiological trade-offs. However, slower montane ontogeny may also reflect proximate influences of harsh weather on parental care and offspring development. We experimentally heated and protected nests from rain to ameliorate harsh montane weather conditions for mountain blackeyes (Chlorocharis emiliae), a montane songbird living at approximately 3,200 m asl in Malaysian Borneo. This experiment was designed to test whether cold and wet montane conditions contribute to parental care and postnatal growth and development rates at high elevations. We found that parents increased provisioning and reduced time spent warming offspring, which grew faster and departed the nest earlier compared with offspring from unmanipulated nests. Earlier departure reduces time-dependent predation risk, benefitting parents and offspring. These plastic responses highlight the importance of proximate weather contributions to broad patterns of montane ontogeny and parental care.
  7. Ord TJ, Blazek K, White TE, Das I
    Proc Biol Sci, 2021 Jun 09;288(1952):20210706.
    PMID: 34102889 DOI: 10.1098/rspb.2021.0706
    Social animals are expected to face a trade-off between producing a signal that is detectible by mates and rivals, but not obvious to predators. This trade-off is fundamental for understanding the design of many animal signals, and is often the lens through which the evolution of alternative communication strategies is viewed. We have a reasonable working knowledge of how conspecifics detect signals under different conditions, but how predators exploit conspicuous communication of prey is complex and hard to predict. We quantified predation on 1566 robotic lizard prey that performed a conspicuous visual display, possessed a conspicuous ornament or remained cryptic. Attacks by free-ranging predators were consistent across two contrasting ecosystems and showed robotic prey that performed a conspicuous display were equally likely to be attacked as those that remained cryptic. Furthermore, predators avoided attacking robotic prey with a fixed, highly visible ornament that was novel at both locations. These data show that it is prey familiarity-not conspicuousness-that determine predation risk. These findings replicated across different predator-prey communities not only reveal how conspicuous signals might evolve in high predation environments, but could help resolve the paradox of aposematism and why some exotic species avoid predation when invading new areas.
  8. Martin TE, Oteyza JC, Mitchell AE, Potticary AL, Lloyd P
    Am Nat, 2015 Mar;185(3):380-9.
    PMID: 25674692 DOI: 10.1086/679612
    Growth and development rates may result from genetic programming of intrinsic processes that yield correlated rates between life stages. These intrinsic rates are thought to affect adult mortality probability and longevity. However, if proximate extrinsic factors (e.g., temperature, food) influence development rates differently between stages and yield low covariance between stages, then development rates may not explain adult mortality probability. We examined these issues based on study of 90 songbird species on four continents to capture the diverse life-history strategies observed across geographic space. The length of the embryonic period explained little variation (ca. 13%) in nestling periods and growth rates among species. This low covariance suggests that the relative importance of intrinsic and extrinsic influences on growth and development rates differs between stages. Consequently, nestling period durations and nestling growth rates were not related to annual adult mortality probability among diverse songbird species within or among sites. The absence of a clear effect of faster growth on adult mortality when examined in an evolutionary framework across species may indicate that species that evolve faster growth also evolve physiological mechanisms for ameliorating costs on adult mortality. Instead, adult mortality rates of species in the wild may be determined more strongly by extrinsic environmental causes.
  9. Jin H, Friedman MR, Lim SH, Guadamuz TE, Wei C
    LGBT Health, 2016 Dec;3(6):465-471.
    PMID: 26982598
    PURPOSE: Men who have sex with men and are sex workers (MSMSW) are disproportionately affected by the growing and emerging HIV epidemic. As sex work and same-sex behavior are heavily stigmatized and often illegal in most Asian countries, HIV research focusing on MSMSW has been limited. The goal of this analysis is to examine HIV testing practices and identify correlates of HIV testing among MSMSW in Asia.

    METHODS: The Asia Internet MSM Sex Survey, an online cross-sectional survey of 10,861 men who have sex with men (MSM), was conducted in 2010. Data on sociodemographic characteristics, HIV testing behaviors, and sexual behaviors were collected. Five hundred and seventy-four HIV-negative/unknown respondents reported receiving payment for sex with men at least once in the past 6 months and were included in this analysis. Multivariable logistic regression was conducted to identify independent correlates of HIV testing in the past year.

    RESULTS: About half (48.6%) of the participants had been tested for HIV at least once within the past year, and 30.5% had never been tested. We also found that MSMSW participants who engaged in risky behaviors were less likely to be tested.

    CONCLUSION: While one might expect a high HIV testing rate among MSMSW due to the risks associated with engaging in sex work, we found that HIV testing uptake is suboptimal among MSMSW in Asia. These results suggest that targeted HIV prevention and testing promotion among MSMSW are needed.

  10. Guadamuz TE, Cheung DH, Wei C, Koe S, Lim SH
    PLoS One, 2015;10(5):e0126658.
    PMID: 25973907 DOI: 10.1371/journal.pone.0126658
    BACKGROUND: Poor HIV testing uptake by MSM may be attributable to unique challenges that are localized in Southeast Asia.

    OBJECTIVE: To characterize MSM who never tested for HIV, to identify correlates of never testing, and to elucidate the perceived barriers to HIV testing.

    METHODS: The present study used data from the Asian Internet MSM Sex Survey (AIMSS) and restricted the analysis to 4,310 MSM from the ten member countries of the Association of South East Asian Nations (ASEAN).

    RESULTS: Among MSM participants from ASEAN in our sample, 1290 (29.9%) reported having never been tested for HIV, 471 (10.9%) tested for HIV more than 2 years ago, and 2186 (50.7%) reported their last test date was between 6 months and two years ago, with only 363 (8.4%) of these men having been tested in the past 6 months. In multivariable logistic regression, younger MSM (age 15-22 years old [AOR: 4.60, 95% CI: 3.04-6.96]), MSM with lower education (secondary school or lower [AOR: 1.37, 95% CI: 1.03-1.83]), MSM who identify as bisexual or heterosexual (compared to gay-identified) (AOR: 1.94, 95% CI: 1.60-2.35), and MSM who had never used a condom with male partners (AOR: 1.61, 95% CI: 1.32-1.97) had higher odds of never been HIV tested. Main reason for not being tested was a low risk perception of HIV exposure (n = 390, 30.2%).

    CONCLUSION: Current HIV prevention response must not leave MSM "in the dark," but instead meet them where they are by utilizing the Internet creatively through social media and smart phones. As ASEAN Economic Community (AEC) is quickly becoming a reality, so must there be an equally fast and united response to slowing down the HIV epidemics among MSM in ASEAN.

  11. Lim SH, Cheung DH, Guadamuz TE, Wei C, Koe S, Altice FL
    Drug Alcohol Depend, 2015 Jun 1;151:31-7.
    PMID: 25865907 DOI: 10.1016/j.drugalcdep.2015.02.040
    BACKGROUND: High prevalence of substance use among men who have sex with men (MSM) may drive the HIV epidemic in Malaysia but patterns of substance use among Malaysian MSM have not been examined. Our study investigated specific Malaysian MSM risk groups to determine the association between their substance use and sexual risk behaviors.
    METHODS: Data from Malaysian respondents (n=1235) in a large, multinational online survey of Asian MSM in 2010 were used to identify latent classes of substance use. Subsequent covariates were included in a joint model to predict class membership.
    RESULTS: The 3-class model was identified as the best fitting model, which included: (1) 'negligible substance use' for those reporting none or using any substance sparingly; (2) 'soft substance use' for those using poppers, ecstasy and drinking before sex; and (3) 'amphetamine-type stimulant (ATS) use' for those using stimulants (methamphetamine, ecstasy), erectile dysfunction drugs and recreational drug use before sex. Men in the 'ATS use' category were significantly less likely to not know their HIV status (AOR: 0.30, 95%CI: 0.14,0.66), more likely to have had more than 6 male sex partners (AOR: 4.83, 95% CI: 1.92-12.2), to have group sex (AOR:4.07, 95% CI: 2.31-7.15), to report inconsistent condom use (AOR:2.01, 95% CI: 1.12-3.60), to be HIV-infected (AOR:3.92, 95% CI: 1.63-8.42) and to have had any sexually transmitted infections (AOR:3.92, 95% CI:1.70, 9.08), compared to men in the 'negligible substance use' category.
    CONCLUSIONS: Our study identified subgroups of Malaysian MSM with distinct substance use patterns and HIV-related risk profiles, which provides implication for targeting HIV prevention in this subpopulation.
  12. Samoh N, Peerawaranun P, Jonas KJ, Lim SH, Wickersham JA, Guadamuz TE
    Sex Transm Dis, 2020 Aug 24.
    PMID: 32842048 DOI: 10.1097/OLQ.0000000000001271
    An online assessment among -social media-using YMSM found that 87% were willing to use HIV self-testing with online supervision (HIVSTOS). Correlates included never tested, having higher numbers of sexual partners and seeking partners online. HIVSTOS may be appropriate for YMSM who have high risks and may not access venue-based settings.
  13. Kongjareon Y, Samoh N, Lim SH, Peerawaranun P, Jonas KJ, Guadamuz TE
    AIDS Care, 2020 08;32(8):954-958.
    PMID: 32160793 DOI: 10.1080/09540121.2020.1734174
    HIV-related factors and suicide-risk status were assessed among YMSM aged 18-24 years recruited through various MSM-related online social apps in Bangkok (N = 1394). The online survey assessed demographic characteristics, sexual behaviours and suicide-risk status. Measure of suicide risk was taken from the Suicidal Behaviors Questionnaire-Revised (cut-off score of seven or higher). Among participants, 249 (17.9%) reported suicide-risk. In multivariable logistic regression, correlates of suicide-risk status included having sometimes or often ever participated in group sex (AOR=1.58, 95% CI: 1.17-2.14), having received money or opportunities for sex (AOR=1.54, 95% CI: 1.09-2.17), often seeking partners online (AOR=1.59, 95% CI: 1.05-2.39), inconsistent condom use (AOR=1.67, 95% CI: 1.26-2.21), and self-assessed as having "medium" or "high" HIV risk (AOR=2.53, 95% CI: 1.61-3.98 and AOR=3.35, 95% CI: 1.92-5.82, respectively). Findings suggest that HIV risk behaviours shown by YMSM are significantly associated with higher risk of suicide.
  14. Shrestha R, Galka JM, Azwa I, Lim SH, Guadamuz TE, Altice FL, et al.
    Transgend Health, 2020;5(3):182-190.
    PMID: 32923668 DOI: 10.1089/trgh.2019.0085
    Background: While global research on the implementation of HIV self-testing (HIVST) has increased exponentially, few studies have assessed information on HIVST uptake factors (i.e., willingness, preferences) in transgender women (TW) and none in the Malaysian context. We therefore sought to assess willingness to use HIVST among this understudied key population. Methods: A cross-sectional survey was conducted among 361 HIV-negative Malaysian TW in 2017. Participants were recruited using flyers, announcements through social media, and direct referral from staff members of the community-based organizations serving the TW communities. Multivariable logistic regression was used to identify correlates of willingness to use HIVST. Results: Nearly half of the participants (47.6%) reported that they would be willing to use HIVST. Multivariable analysis showed that willingness to use HIVST was positively associated with having experienced sexual assault in childhood (adjusted odds ratio [aOR]=3.239, p<0.001), having ever used mobile phone or apps to find sex work clients (aOR=1.677, p=0.040), and having engaged in condomless sex in the past 6 months (aOR=1.886, p=0.018). In contrast, living in Kuala Lumpur (aOR=0.559, p=0.032), having higher number of sex work clients per day (aOR=0.927, p=0.004), and current depressive symptoms (aOR=0.576, p=0.026) were negatively associated with willingness to use HIVST. Conclusions: Findings in this study suggest that TW in our sample were moderately willing to use HIVST. Especially important here is the increased interest in HIVST among TW who are at higher risk for HIV infection. Overall, our findings underscore the need for additional research on how to most effectively implement HIVST for key populations, including TW, such that uptake and retention in regular HIV screening is sustained.
  15. Cheung DH, Samoh N, Jonas K, Lim SH, Kongjareon Y, Guadamuz TE
    Sex Transm Dis, 2024 May 01;51(5):352-358.
    PMID: 38301623 DOI: 10.1097/OLQ.0000000000001937
    BACKGROUND: Human immunodeficiency virus (HIV) testing for Thai men who have sex with men (MSM) is suboptimal, which undermines their linkage to care and subsequent HIV preexposure prophylaxis (PrEP) uptake.

    METHODS: We analyzed a cross-sectional survey conducted in 2021 among Thai MSM who attended any private sex parties or circuit parties in the past 3 years ("sexualized parties").

    RESULTS: Of the 424 men included in our analysis, 47.6% had been recently tested for HIV in the past 1 year, 30.2% had not recently been tested, and 22.2% had never been tested. In our multivariable analysis, relative to participants who had recently tested for HIV, those who have never tested were more likely to have lower education or to live outside of Bangkok, and to have attended both circuit and private sex parties (vs. private sex party only) but were less likely to report any sexually transmitted infection diagnosis or to have heard of PrEP. Participants who had an HIV test more than a year ago were more likely to have attended both circuit and private sex parties (vs. private sex parties only) but were less likely to have any sexually transmitted infection diagnosis, meet sexual partners online, or have heard of PrEP. Rates of condomless anal sex and willingness to use PrEP were similar across groups.

    CONCLUSIONS: Despite the high rates of sexual risk-taking, sexualized party attendees reported suboptimal HIV testing uptake. The joint promotion of HIV testing and PrEP is warranted-especially on-premise HIV testing at circuit parties and outreach at online platforms to reach sexualized party attendees.

  16. Cheung DH, Samoh N, Jonas KJ, Lim SH, Kongjareon Y, Guadamuz TE
    Arch Sex Behav, 2024 Oct;53(9):3527-3536.
    PMID: 39150645 DOI: 10.1007/s10508-024-02868-8
    Sexualized substance use or "chemsex" may contribute to the HIV epidemic among men who have sex with men (MSM) in Thailand. Specific patterns of chemsex use may be associated with different HIV/STI transmission risks. We examined typologies and correlates of sexualized substance use among a sample of high-risk MSM (n = 532) who had attended a private sex party or circuit party in the past three years using latent class analysis. Multinomial regression was used to adjust for variables associated with the 3-class latent class model. We identified a 3-class model as the best fitting model, which included: (1) "negligible sexualized substance users" (36.7%), who had never engaged in chemsex in the past six months; (2) "sexualized substance users" (13.9%), who had a high level of sexualized alcohol use and a wide range of other substances before or during sex in the past six months; and (3) "exclusive chemsex users" (49.4%), who predominantly used crystal methamphetamine, amyl nitrite, and erectile dysfunctional drugs before or during sex in the past six months. Compared to negligible sexualized substance users, exclusive chemsex users were more likely to be HIV-positive, more likely to have six or more sexual partners in the past six months, less likely to have condom use at last anal intercourse, and more likely to have provided sex work. Relative to negligible sexualized substance users, sexualized substance users reported more frequent online sex-seeking behaviors. These subgroups of Thai MSM have unique substance use patterns and HIV-related risk profiles, underscoring the importance of targeted HIV prevention strategies.
  17. Carter MJ, Frykberg RG, Oropallo A, Sen CK, Armstrong DG, Nair HKR, et al.
    Adv Wound Care (New Rochelle), 2023 Apr;12(4):177-186.
    PMID: 35593010 DOI: 10.1089/wound.2022.0041
    Objective: To conduct a systematic review and meta-analysis of recently published randomized controlled trials (RCTs) that employed the use of topical oxygen therapy (TOT) as an adjunct therapy in the treatment of Wagner 1 and 2 diabetic foot ulcers. Approach: Following a literature search of eligible studies from 2010 onward, four RCTs were included. Studies were analyzed for patient and wound characteristics, outcomes, risk of bias, and quality of the evidence assessed using the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) methodology. A random-effects meta-analysis for complete wound healing was carried out due to statistical heterogeneity of included studies. Results: Risk of bias judgment (RoB2 analysis) resulted in one low-risk trial and three trials with some risk. One study was determined to be the origin of the statistical heterogeneity. Pooled results showed statistical significance with a risk ratio (RR) of 1.59 (95% confidence interval [CI]: 1.07-2.37; p = 0.021). Sensitivity analysis, based on imputed values for missing outcomes, demonstrated that both the RR and 95% CIs changed little. The GRADE ratings for each domain were as follows: (a) risk of bias: moderate (3); (b) imprecision: moderate (2), high (1); (c) inconsistency: low (2), high (1); (d) indirectness: moderate (2), high (1); and (e) publication bias: moderate (1), high (2). Overall, the evidence was moderate. Innovation: Our study shows that TOT is a viable diabetic foot ulcer therapy. Conclusions: These data support the use of TOT for the treatment of chronic Wagner 1 or 2 diabetic foot ulcers in the absence of infection and ischemia.
  18. Cheung DH, Waratworawan W, Kongjareon Y, Jonas KJ, Lim SH, Reeves AN, et al.
    AIDS Behav, 2025 Jan 09.
    PMID: 39779629 DOI: 10.1007/s10461-024-04516-7
    This study investigated the clustering of psychosocial adversities and their synergistic effect with depression on suicidality in a 12-month prospective cohort (N = 214) of YMSM living with HIV in Bangkok, Thailand. Latent class analysis identified subgroups with distinct combinations of adversities, including bullying, intimate partner violence, substance use, HIV stigma, low social support, histories of sex work, and below-income status. Significant interactive synergism were found as hypothesized, supporting a syndemic effect with qualitatively increasing levels of adversities on suicidality (score range: 3-17) over the 12 months. The interaction between moderate adversity clustering and depression (βow = 2.50, 95% CI: 1.12-3.88) and high adversity clustering and depression (βow = 3.61, 95% CI: 1.12-6.09) indicated that the impact of depression on suicidality was modified by pre-existing adversities. The findings suggest that, while a multi-component intervention addressing psychosocial problems is ideal, effective depression treatment alone could significantly reduce suicidality among YMSM living with HIV.
  19. Loo CC, Thomas E, Tan HM, Sia TH
    Med J Malaysia, 1997 Sep;52(3):264-8.
    PMID: 10968096
    We have studied the antiemetic efficacy of droperidol alone, and in combination with metoclopramide in first trimester termination of pregnancy in day surgery. The aim was to determine whether the addition of metoclopramide could further reduce the incidence of postoperative nausea and vomiting (PONV) but avoid excessive sedation. Group I (control, n = 40) received i.v. droperidol 0.625 mg at induction. Group II (study, n = 40) received i.v. droperidol 0.625 mg and i.v. metoclopramide 10 mg at induction. The incidence of nausea at 1 and 2 hours postoperatively was 23% and 10% in group I, and 5% and nil in group II respectively. The difference in the incidence of nausea was significant at p < 0.05 at one hour but not at two hours postoperatively. No patients vomited. There was no difference in the sedation and pain score between them. We did not observe any significant side effects attributable to either drug. All patients were discharged home within 3 hours. We conclude that in the prevention of PONV, the combination of metoclopramide and droperidol is superior to the use of droperidol alone at one hour but not at two hours postoperatively.
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