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Publications (39)

  • Raymond Harris · Emily R Van Dyke · Thanh G N Ton · [...] · Dedra Buchwald
    [Show abstract] [Hide abstract] ABSTRACT: American Indians and Alaska Natives (AI/ANs) experience significant cancer disparities. To inform future public health efforts, a web-based needs assessment survey collected quantitative and qualitative data from AI/AN community health workers and cancer survivors in the northwestern United States. Content analysis of qualitative responses identified themes to contextualize quantitative results. Seventy-six AI/AN respondents (93% female) described substantial unmet needs for education and resources to assist cancer survivors, including a shortage of patient navigators, support groups, and home health care workers. Fear of negative outcomes, a culturally rooted avoidance of discussing illness, and transportation difficulties were cited as major barriers to participation in cancer education and receipt of health services. Face-to-face contact was overwhelmingly preferred for community education and support, but many respondents were receptive to other communication channels, including e-mail, social media, and webinars. Survey results highlight the importance of culturally sensitive approaches to overcome barriers to cancer screening and education in AI/AN communities. Qualitative analysis revealed a widespread perception among respondents that available financial and human resources were insufficient to support AI/AN cancer patients' needs.
    Article · Oct 2015 · Health Promotion Practice
  • Thanh G.N. Ton · Charles Mackenzie · David H. Molyneux
    [Show abstract] [Hide abstract] ABSTRACT: Neglected Tropical Diseases (NTDs) afflict around one billion individuals in the poorest parts of the world with many more at risk. Lymphatic filariasis is one of the most prevalent of the infections and causes significant morbidity in those who suffer the clinical conditions, particularly lymphedema and hydrocele. Depressive illness has been recognised as a prevalent disability in those with the disease because of the stigmatising nature of the condition. No estimates of the burden of depressive illness of any neglected tropical disease have been undertaken to date despite the recognition that such diseases have major consequences for mental health not only for patients but also their caregivers. We developed a mathematical model to calculate the burden of Disability- Adjusted Life Years (DALY) attributable to depressive illness in lymphatic filariasis and that of their caregivers using standard methods for calculating DALYs. Estimates of numbers with clinical disease was based on published estimates in 2012 and the numbers with depressive illness from the available literature. We calculated that the burden of depressive illness in filariasis patients was 5.09 million disability-adjusted life years (DALYs) and 229,537 DALYs attributable to their caregivers. These figures are around twice that of 2.78 million DALYs attributed to filariasis by the Global Burden of Disease study of 2010. Lymphatic filariasis and other neglected tropical diseases, notably Buruli Ulcer, cutaneous leishmaniasis, leprosy, yaws, onchocerciasis and trachoma cause significant co morbidity associated with mental illness in patients. Studies to assess the prevalence of the burden of this co-morbidity should be incorporated into any future assessment of the Global Burden of neglected tropical diseases. The prevalence of depressive illness in caregivers who support those who suffer from these conditions is required. Such assessments are critical for neglected tropical diseases which have such a huge global prevalence and thus will contribute a significant burden of co-morbidity attributable to mental illness.
    Article · Jul 2015 · Infectious Diseases of Poverty
  • [Show abstract] [Hide abstract] ABSTRACT: Parkinson disease (PD) is the second most common neurodegenerative disorder. Its diagnosis relies solely on a clinical examination and is not straightforward because no diagnostic test exists. Large, population-based, prospective cohort studies designed to examine other outcomes that are more common than PD might provide cost-efficient alternatives for studying the disease. However, most cohort studies have not implemented rigorous systematic screening for PD. A majority of epidemiologic studies that utilize population-based prospective designs rely on secondary data sources to identify PD cases. Direct validation of these secondary sources against clinical diagnostic criteria is lacking. The Framingham Heart Study has prospectively screened and evaluated participants for PD based on clinical diagnostic criteria. We assessed the predictive value of secondary sources for PD identification relative to clinical diagnostic criteria in the Framingham Heart Study (2001-2012). We found positive predictive values of 1.0 (95% confidence interval: 0.868, 1.0), 1.0 (95% confidence interval: 0.839, 1.0), and 0.50 (95% confidence interval: 0.307, 0.694) for PD identified from self-report, use of antiparkinsonian medications, and Medicare claims, respectively. The negative predictive values were all higher than 0.99. Our results highlight the limitations of using only Medicare claims data and suggest that population-based cohorts may be utilized for the study of PD determined via self-report or medication inventories while preserving a high degree of confidence in the validity of PD case identification. © The Author 2014. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail:
    Article · Dec 2014 · American Journal of Epidemiology
  • Thanh G N Ton · Sophia P Gladding · Joseph R Zunt · [...] · Joseph C Kolars
    [Show abstract] [Hide abstract] ABSTRACT: The Fogarty International Center (FIC) Global Health Fellows Program provides trainees with the opportunity to develop research skills through a mentored research experience, increase their content expertise, and better understand trends in global health research, funding organizations, and pathways to generate support. The Northern Pacific Global Health Fellows Research and Training Consortium, which hosts one of the FIC Global Health Programs, sought to enhance research training by developing, implementing, and evaluating a competency-based curriculum that uses a modular, asynchronous, web-based format. The curriculum has 8 core competencies, 36 learning objectives, and 58 assignments. Nineteen trainees completed their 11-month fellowship, engaged in the curriculum, and provided pre- and post-fellowship self-assessments. Self-assessed scores significantly improved for all competencies. Trainees identified the curriculum as one of the strengths of the program. This competency-based curriculum represents a first step toward creating a framework of global health research competencies on which further efforts could be based.
    Article · Nov 2014 · The American journal of tropical medicine and hygiene
  • Jessica I. Lundin · Thanh G. N. Ton · Andrea Z. LaCroix · [...] · Harvey Checkoway
    [Show abstract] [Hide abstract] ABSTRACT: Hormone therapy (HT) is a class of medications widely prescribed to women in the Western world. Evidence from animal models and in vitro studies suggests that estrogen may protect against nigrostriatal system injury and increase dopamine synthesis, metabolism, and transport. Existing epidemiologic research indicates a possible reduced risk of Parkinson's disease (PD) associated with HT use. The objective of this study was to evaluate PD risk associated with specific HT formulations. Neurologist-confirmed cases and age-matched controls were identified from Group Health Cooperative (GHC) of Washington State. Final analysis included 137 female cases and 227 controls. Hormone therapy use was ascertained from the GHC pharmacy database, further classified as conjugated estrogens, esterified estrogens, and progestin. Ever use of HT formulation demonstrated a suggested elevated risk with esterified estrogen use (odds ratio [OR], 3.1; 95% confidence interval [CI], 1.0-9.8), and no risk associated with conjugated estrogen use (OR, 0.6; 95% CI, 0.6-1.3). Restricting this analysis to prescriptions that included progestin further elevated the risk associated with esterified estrogen use (OR, 6.9; 95% CI, 2.1-22.9); again, no risk was associated with conjugated estrogen use (OR, 1.7; 95% CI, 0.6-5.0). The findings from this study suggest an increase in PD risk associated with esterified estrogen use combined with progestin, and no risk associated with conjugated estrogen with progestin. These findings could have important implications for choice of HT in clinical practice. © 2014 International Parkinson and Movement Disorder Society
    Article · Nov 2014 · Movement Disorders
  • [Show abstract] [Hide abstract] ABSTRACT: Objective We characterized functional impact of narcolepsy on patients using a general health status measure, the Sickness Impact Profile (SIP). It has 136 items grouped into 12 categories and 2 dimensions. Methods We ascertained patients with physician-diagnosed narcolepsy in King County, Washington using multiple overlapping methods over four years starting July 2001. We recruited 226 patients (mean age 48 years, 65% female) who underwent in-person interviews and completed: Epworth Sleepiness Scale (ESS), Ullanlinna Narcolepsy Scale (UNS), and SIP. Linear regression was used to assess correlations between measures. Results Mean percent of total dysfunction was higher for psychosocial dimension (13.2) and independent categories (13.4) than physical dimension (5.0). Mean percent of total dysfunction in descending order for categories was: Sleep and Rest (23.6), Alertness Behavior (22.6), and Recreation and Pastimes (20.6). Ten items were endorsed by at least a third of all patients but only two of them concerned sleep. Unexpectedly, among the top ten items were, “My sexual activity is decreased,” and “I forget a lot, for example, things that happened recently, where I put things, appointments.” Percent of overall dysfunction on SIP (mean 10.3) was significantly correlated with ESS (r=0.36, p<0.001) and UNS (r=0.47, p<0.001). In this population-based sample, mean percent of total dysfunction on SIP in patients with narcolepsy (10.3) was higher than previously reported in the general population (3.6) and similar to that in other chronic disabling conditions. Discussion The SIP correlated with ESS and UNS, and captured unique aspects of the impact of narcolepsy on patients.
    Article · Mar 2014 · Sleep Science
  • Thanh G N Ton · Mary Lou Biggs · Diane Comer · [...] · Samay Jain
    [Show abstract] [Hide abstract] ABSTRACT: We sought to improve a previous algorithm to ascertain Parkinson's disease (PD) in the Cardiovascular Health Study by incorporating additional data from Medicare outpatient claims. We compared our results to the previous algorithm in terms of baseline prevalence and incidence of PD, as well as associations with baseline smoking characteristics. Our original case ascertainment used self-reported diagnosis, antiparkinsonian medication, and hospitalization discharge International Classification of Diseases-Ninth version code. In this study, we incorporated additional data from fee-for-service Medicare claims, extended follow-up time, review of hospitalization records, and adjudicated cause of death. Two movement disorders specialists adjudicated final PD status. We used logistic regression models and controlled for age, sex, African American race, and education. We identified 75 additional cases but reclassified 80 previously identified cases as not having PD. We observed significant inverse association with smoking status (odds ratio = 0.42; 95% confidence interval (CI) = 0.22, 0.79), and inverse linear trends with pack-years (p = 0.005), and cigarettes per day (p = 0.019) with incident PD. All estimates were stronger than those from the previous algorithm. Our enhanced method did not alter prevalence and incidence estimates compared with our previous algorithm. However, our enhanced method provided stronger estimates of association, potentially due to reduced level of disease misclassification. Copyright © 2013 John Wiley & Sons, Ltd.
    Article · Feb 2014 · Pharmacoepidemiology and Drug Safety
  • Carlos Abanto · Thanh G N Ton · David L Tirschwell · [...] · Joseph Zunt
    [Show abstract] [Hide abstract] ABSTRACT: Background: Because of the aging population in low- and middle-income countries, cerebrovascular disease is expected to remain a leading cause of death. Little has been published about stroke in Peru. We conducted a retrospective cohort study of hospitalized stroke patients at a referral center hospital in Lima, Peru to explore factors associated with functional outcome among stroke patients. Methods: We identified 579 patients hospitalized for ischemic stroke or intracerebral hemorrhage stroke at the National Institute of Neurologic Sciences in Lima, Peru in 2008 and 2009. A favorable outcome was defined as a modified Rankin scale score of ≤ 2 at discharge. Results: The mean age was 63.3 years; 75.6% had ischemic stroke; the average duration of stay was 17.3 days. At hospital discharge, 231 (39.9%) had a favorable outcome. The overall mortality rate was 5.2%. In multivariate models, the likelihood of having a favorable outcome decreased linearly with increasing age (P = .02) and increasing National Institutes of Health Stroke Scale (NIHSS) score (P = .02). Favorable outcome was also associated with male gender (relative risk [RR] 1.2; 95% confidence interval [CI] 1.0-1.5) and divorced status (RR 1.3; 95% CI 1.1-1.7). Patients on Salud Integral de Salud (SIS; public assistance-type insurance; RR 0.7; 95% CI 0.5-1.0) were also less likely to have a favorable outcome. Conclusions: Favorable outcome after stroke was independently associated with younger age, a lower NIHSS score, male gender, being divorced, and not being on SIS insurance. These findings suggest that additional study of worse functional outcomes in patients with SIS insurance be conducted and confirm the importance of risk adjustment for age, stroke severity (according to the NIHSS scale), and other socioeconomic factors in outcomes studies. Future studies should preferentially assess outcome at 30 days and 6 months to provide more reliable comparisons and allow additional study of Peruvian end-of-life decision-making and care.
    Article · Jan 2013 · Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association
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    David L Tirschwell · Thanh G N Ton · Kiet A Ly · [...] · Annette L Fitzpatrick
    [Show abstract] [Hide abstract] ABSTRACT: Background As low and middle-income countries such as Vietnam experience the health transition from infectious to chronic diseases, the morbidity and mortality from stroke will rise. In line with the recommendation of the Institute of Medicine’s report on “Promoting Cardiovascular Health in the Developing World” to “improve local data”, we sought to investigate patient characteristics and clinical predictors of mortality among stroke inpatients at Da Nang Hospital in Vietnam. Methods A stroke registry was developed and implemented at Da Nang Hospital utilizing the World Health Organization’s Stroke STEPS instrument for data collection. Results 754 patients were hospitalized for stroke from March 2010 through February 2011 and admitted to either the intensive care unit or cardiology ward. Mean age was 65 years, and 39% were female. Nearly 50% of strokes were hemorrhagic. At 28-day follow-up, 51.0% of patients with hemorrhagic stroke died whereas 20.3% of patients with ischemic stroke died. A number of factors were independently associated with 28-day mortality; the two strongest independent predictors were depressed level of consciousness on presentation and hemorrhagic stroke type. While virtually all patients completed a CT during the admission, evidence-based processes of care such as anti-thrombotic therapy and carotid ultrasound for ischemic stroke patients were underutilized. Conclusions This cohort study highlights the high mortality due in part to the large proportion of hemorrhagic strokes in Vietnam. Lack of hypertension awareness and standards of care exacerbated clinical outcomes. Numerous opportunities for simple, inexpensive interventions to improve outcomes or reduce recurrent stroke have been identified.
    Full-text Article · Dec 2012 · BMC Neurology
  • [Show abstract] [Hide abstract] ABSTRACT: Viet Nam is experiencing a health transition from infectious to chronic disease. Data on cardiovascular diseases, including strokes, are limited. Data were randomly collected from six communities in Da Nang, Viet Nam, on participant demographics, medical history, blood pressure, anthropometrics and health behavior using World Health Organization (WHO) guidelines. Stroke symptoms were collected by self-report with the standardized Questionnaire for Verifying Stroke Free Status. Multivariate logistic regression was used to identify factors associated with the presence of stroke symptoms. 1,621 adults were examined with a mean age of 52.0 years (± 12.5 years), of which 56.1% were women. 27.3% of the participants were found to have hypertension, 26.2% used tobacco, and 16.1% were overweight. More than two-thirds of the participants with hypertension were unaware of their condition. Almost one fourth of the participants were identified by the questionnaire as previously experiencing at least one stroke symptom. Age, rural residence, and education were associated with the presence of stroke symptoms. Models adjusted for demographics found hypertension, high cholesterol, reported severe chest pain, former smoking, and being overweight to be associated with a higher prevalence of stroke symptoms. The high frequency of stroke symptoms in Da Nang calls for further evaluation and interventions to reduce hypertension and other risk factors for chronic disease.
    Article · Sep 2012 · Journal of Epidemiology and Global Health
  • [Show abstract] [Hide abstract] ABSTRACT: Abstract Human papillomavirus (HPV) infection among men who have sex with men (MSM) is the primary risk factor for anal cancer. Of 105 Peruvian MSM examined, 77.1% were infected with HPV; of these 79.0% were coinfected with two or more types and 47.3% were infected by a carcinogenic type. HPV types 53, 6, 16, and 58 were the most frequent HPV infections detected. High-risk HPV type infection was associated with sex work, HIV status, and having rectal chlamydial or gonorrheal infection. These findings support broadening HPV vaccine coverage and increasing surveillance for the development of cancer in MSM infected with HPV.
    Article · Apr 2012 · AIDS research and human retroviruses
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    Angela A Gonzales · Eva Garroutte · Thanh G N Ton · [...] · Dedra Buchwald
    [Show abstract] [Hide abstract] ABSTRACT: American Indians have one of the lowest colorectal cancer (CRC) screening rates for any racial/ethnic group in the U.S., yet reasons for their low screening participation are poorly understood. We examine whether tribal language use is associated with knowledge and use of CRC screening in a community-based sample of American Indians. Using logistic regression to estimate the association between tribal language use and CRC test knowledge and receipt we found participants speaking primarily English were no more aware of CRC screening tests than those speaking primarily a tribal language (OR = 1.16 [0.29, 4.63]). Participants who spoke only a tribal language at home (OR = 1.09 [0.30, 4.00]) and those who spoke both a tribal language and English (OR = 1.74 [0.62, 4.88]) also showed comparable odds of receipt of CRC screening. Study findings failed to support the concept that use of a tribal language is a barrier to CRC screening among American Indians.
    Full-text Article · Mar 2012 · Journal of Immigrant and Minority Health
  • [Show abstract] [Hide abstract] ABSTRACT: Birth order may play a role in autoimmune diseases and early childhood infections, both factors implicated in the etiology of narcolepsy. We investigated the association between birth order and narcolepsy risk in a population-based case-control study in which all study subjects were HLA-DQB1*0602 positive. Subjects were 18-50 years old, residents of King County, Washington, and positive for HLA-DQB1*0602. Birth order was obtained from administered interviews. We used logistic regression to generate odds ratios adjusted for income and African American race. Analyses included 67 cases (mean age 34.3 [SD=9.1], 70.2% female) and 95 controls (mean age 35.1 [SD=8.8], 58.1% female). Associations for birth order were as follows: first born (cases 38.8% vs. controls 50.2%, OR=1.0; reference), second born (cases 29.9% vs. controls 32.9%, OR=1.6; 95% CI 0.7, 3.7), and third born or higher (cases 31.3% vs. controls 16.8%, OR=2.5; 95% CI 1.0, 6.0). A linear trend was significant (p<0.05). Sibling number, sibling gender, having children, and number of children did not differ significantly between narcolepsy cases and controls. Narcolepsy risk was significantly associated with higher birth order in this population-based study of genetically susceptible individuals. This finding supports an environmental influence on narcolepsy risk through an autoimmune mechanism, early childhood infections, or both.
    Article · Mar 2012 · Sleep Medicine
  • Thanh G N Ton · Samay Jain · Mary L Biggs · [...] · Harvey Checkoway
    [Show abstract] [Hide abstract] ABSTRACT: Studies demonstrate existence of inflammation in prevalent Parkinson's disease (PD). We assessed associations of baseline levels of inflammatory markers with prevalent PD at baseline (1989) and incident PD identified over 13 years of follow-up of the Cardiovascular Health Study. Blood samples at baseline were measured for fibrinogen, interleukin-6, tumor necrosis factor-α, C-reactive protein, albumin, and white blood cells. The analysis included 60 prevalent and 154 incident PD cases. Risk of prevalent PD was significantly higher per doubling of IL-6 among women (odds ratio [OR]=1.5, 95% confidence interval [CI]: 1.0, 2.4) and WBC among men (OR: 2.4, 95% CI: 1.2, 4.9) in multivariate models. Risk of incident PD was not associated with higher levels of any biomarker after adjusting for age, smoking, African American race, and history of diabetes. Inverse associations with incident PD were observed per doubling of C-reactive protein (OR=0.9; 95% CI: 0.8, 1.0) and of fibrinogen among women (OR=0.4; 95% CI: 0.2, 0.8). Although inflammation exists in PD, it may not represent an etiologic factor. Our findings suggest the need for larger studies that measure inflammatory markers before PD onset.
    Article · Nov 2011 · Parkinsonism & Related Disorders
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    [Show abstract] [Hide abstract] ABSTRACT: Growing evidence supports the hypothesis that narcolepsy with cataplexy is an autoimmune disease. We here report genome-wide association analyses for narcolepsy with replication and fine mapping across three ethnic groups (3,406 individuals of European ancestry, 2,414 Asians and 302 African Americans). We identify a SNP in the 3' untranslated region of P2RY11, the purinergic receptor subtype P2Y₁₁ gene, which is associated with narcolepsy (rs2305795, combined P = 6.1 × 10⁻¹⁰, odds ratio = 1.28, 95% CI 1.19-1.39, n = 5689). The disease-associated allele is correlated with reduced expression of P2RY11 in CD8(+) T lymphocytes (339% reduced, P = 0.003) and natural killer (NK) cells (P = 0.031), but not in other peripheral blood mononuclear cell types. The low expression variant is also associated with reduced P2RY11-mediated resistance to ATP-induced cell death in T lymphocytes (P = 0.0007) and natural killer cells (P = 0.001). These results identify P2RY11 as an important regulator of immune-cell survival, with possible implications in narcolepsy and other autoimmune diseases.
    Full-text Article · Oct 2011 · Nature Genetics
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    Full-text Article · Sep 2011 · Nature Genetics
  • Thanh G N Ton · Thomas T Fogg · Chin-To Fong · [...] · Thomas A Pearson
    Article · Aug 2011 · Circulation
  • [Show abstract] [Hide abstract] ABSTRACT: To determine the prevalence and risk factors for human papillomavirus (HPV) infection in female sex workers (FSW) in Lima, Peru. Cross-sectional study of 87 FSW. Information regarding demographics, sex work practices, and genital and blood specimens was collected. Forty-four (50.6%) of 87 FSW had HPV detected in cervical swabs. The prevalence of coinfection by two or more HPV types was 39.1%. Thirty-one (35.6%) were infected by at least one high-risk HPV type, representing 70.5% of women with HPV infection. HPV infection was associated with younger age but not with any demographic or sexual characteristics. Our study confirms the high prevalence of HPV infection in FSW reported by other groups and suggests that brothel-based FSW may be at lower risk for acquiring high-risk HPV infection.
    Article · Feb 2011 · Sexually transmitted infections
  • Ton TG · Fogg TT · Fong CT · [...] · Pearson TA
    Article · Jan 2011 · Circulation
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    Full-text Dataset · Dec 2010