Thanh G N Ton

University of Washington Seattle, Seattle, Washington, United States

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Publications (26)203.48 Total impact

  • [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.
    Pharmacoepidemiology and Drug Safety 12/2013; · 2.90 Impact Factor
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    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.
    Journal of stroke and cerebrovascular diseases: the official journal of National Stroke Association 01/2013;
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    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.
    Journal of epidemiology and global health. 09/2012; 2(3):155-163.
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    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.
    AIDS research and human retroviruses 04/2012; · 2.18 Impact Factor
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    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.
    Journal of Immigrant and Minority Health 03/2012; · 1.16 Impact Factor
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    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.
    Sleep Medicine 03/2012; 13(3):310-3. · 3.49 Impact Factor
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    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.
    Parkinsonism & Related Disorders 11/2011; 18(3):274-8. · 3.27 Impact Factor
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    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.
    Sexually transmitted infections 02/2011; 87(1):81-2. · 2.18 Impact Factor
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    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.
    Nature Genetics 01/2011; 43(1):66-71. · 35.21 Impact Factor
  • Nature Genetics 01/2011; 43(10):1040. · 35.21 Impact Factor
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    ABSTRACT: Photovoice, a qualitative methodology using photography by study participants, is an ideal tool for collecting information on awareness of cardiovascular health from the perspective of persons of different cultural backgrounds and English-speaking abilities who are often subject to health disparities. Participants of Chinese, Vietnamese, and Korean ethnicity were provided disposable cameras to photograph their perceptions of scenes promoting or acting as barriers to cardiovascular health. After the pictures were developed, they returned for a discussion in their native languages to contextualize the stories told in their photographs. Group facilitators spoke the respective native languages and transcribed sessions into English. Twenty-three adults participated (7 to 9 persons per ethnicity), ranging in age from 50 to 88 (mean 71.6) years; 48% were women. The photographs stimulated conversations of knowledge, beliefs, and concerns regarding heart disease and stroke. Issues surrounding food and exercise were most dominant across ethnic groups, focusing on fat and salt intake and the need to remain active. Cultural beliefs and issues of emotional health, including stress and loneliness related to living in a new country, were also depicted. Photovoice provided insight into perceptions of cardiovascular health that is vital for developing health promotion and education interventions in limited-English-speaking communities.
    Health Promotion Practice 11/2010; 13(1):48-54. · 0.55 Impact Factor
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    Journal of clinical sleep medicine: JCSM: official publication of the American Academy of Sleep Medicine 08/2010; 6(4):406. · 2.93 Impact Factor
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    ABSTRACT: One etiologic model for narcolepsy suggests that some environmental toxin selectively and irreversibly destroys hypocretin-producing cells in individuals with human leukocyte antigen (HLA) DQB1(*)0602. Between 2001 and 2005, the authors conducted a population-based case-control study in King County, Washington to examine narcolepsy risk in relation to toxins found in jobs, hobbies, and other non-vocational activities. Sixty-seven cases and 95 controls were enrolled; all were between ages 18 and 50 and positive for HLA DQB1(*)0602. All were administered in-person interviews about jobs, hobbies or other non-vocational activities before age 21. All analyses were adjusted for African-American race and income. Risk increased significantly for jobs involving heavy metals (odds ratio [OR]=4.7; 95% confidence interval [CI]: 1.5, 14.5) and for highest levels of exposure to woodwork (OR: 3.0; 95% CI: 1.0, 8.9), fertilizer (OR=3.1; 95% CI: 1.1, 9.1), and bug or weed killer (OR=4.5; 95% CI: 1.5, 13.4). Associations were of borderline significance for activities involving ceramics, pesticides, and painting projects. Significant dose-response relationships were evident for jobs involving metals (p<0.03), paints (p<0.03), and bug or weed killer (p<0.02). Additional studies are needed to replicate these findings and continue the search for specific toxins that could damage hypocretin neurons in genetically susceptible people.
    Environmental Research 08/2010; 110(6):565-70. · 3.24 Impact Factor
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    ABSTRACT: Cardiovascular disease (CVD) is the leading cause of death among Asian Americans, the majority of whom are foreign-born. However, CVD and risk factor data is sparse for specific Asian immigrant populations. To assess knowledge and understanding of CVD and risk factors within Chinese, Korean and Vietnamese immigrant populations, we conducted eight focus groups of 77 participants between 36 and 84 years old. Participants correctly identified signs and symptoms for heart attacks while knowledge about stroke was incomplete. While poor diet, lack of exercise, older age, and high cholesterol were frequently discussed as risk factors, mechanisms perceived as contributing to heart disease were influenced primarily by non-Western paradigms. Non-Western remedies were discussed in detail among Chinese and Vietnamese participants. All participants desired more information, and identified barriers to effective communication with healthcare providers. A deeper understanding of beliefs and barriers faced by Asian immigrants can help guide health promotion efforts.
    Journal of Immigrant and Minority Health 03/2010; 13(1):127-39. · 1.16 Impact Factor
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    ABSTRACT: To investigate associations between HLA-DQB1*0602 allele status and measures of narcolepsy symptom severity. Cross-sectional study of population-based narcolepsy patients. King County, Washington. All prevalent cases (n = 279) of physician-diagnosed narcolepsy ascertained from 2001-2005. N/A. Narcolepsy diagnosis was based on cataplexy status, diagnostic sleep study results, and chart review. The number of HLA-DQB1 alleles was determined from buccal genomic DNA. Symptom severity instruments included the Epworth Sleepiness Scale (ESS), the Ullanlinna Narcolepsy Scale (UNS), age of symptom onset, subjective sleep latency and duration, and various clinical sleep parameters. We used linear regression adjusted for African American race and an extended chi-square test of trend to assess relationships across ordered groups defined by allele number (0, 1, or 2). Narcolepsy patients were 63% female and 82% Caucasian, with a mean age of 47.6 years (SD = 17.1). One hundred forty-one (51%) patients had no DQB1*0602 alleles; 117 (42%) had one; and 21 (7%) had two. In the complete narcolepsy sample after adjustment for African American race, we observed a linear relationship between HLA-DQB1*0602 frequency and sleepiness as defined by the ESS (P < 0.01), narcolepsy severity as defined by UNS (P < 0.001), age of symptom onset (P < 0.05), and sleep latency (P < 0.001). In univariate analyses, HLA-DQB1*0602 frequency was also associated with napping (P < 0.05) and increased car and work accidents or near accidents (both P < 0.01). Habitual sleep duration was not associated with HLA status. These race-adjusted associations remained for the ESS (P < 0.05), UNS (P < 0.01), and sleep latency (P < 0.001) when restricting to narcolepsy with cataplexy. Narcolepsy symptom severity varies in a linear manner according to HLA-DQB1*0602 allele status. These findings support the notion that HLA-DQ is a disease-modifying gene.
    Sleep 01/2010; 33(1):29-35. · 5.10 Impact Factor
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    ABSTRACT: Perceived risk of disease plays a key role in health behaviors, making it an important issue for cancer-prevention research. We investigate associations between perceived cancer risk and selected cancer risk factors in a population-based sample of American Indians. STUDY DESIGN AND POPULATION: Data for this cross-sectional study come from a random sample of 182 American Indian adults, aged > or = 40 years, residing on the Hopi Reservation in northeastern Arizona. Perception of cancer risk was ascertained with the 5-point Likert scale question, "How likely do you think it is that you will develop cancer in the future?" dichotomized into low perceived risk and high perceived risk. Participants reporting a family member with cancer were more likely, by greater than five times, to report the perception that they would get cancer (OR = 5.3; 95% CI: 2.3, 12.3). After controlling for age and family history of cancer, knowledge of cancer risk factors and attitude about cancer prevention were not significantly associated with risk perception. Perceived cancer risk was significantly associated with self-reported family history of cancer, supporting the importance of personal knowledge of cancer among American Indians. Further research is needed to obtain a more complete picture of the factors associated with perceptions of cancer risk among American Indians in order to develop effective interventions.
    Ethnicity & disease 01/2010; 20(4):458-62. · 1.12 Impact Factor
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    Sleep 12/2009; 32(12):1548. · 5.10 Impact Factor
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    American Journal of Public Health 12/2009; 99(12):2147-9. · 3.93 Impact Factor
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    ABSTRACT: Epidemiological observations suggest that exposures in youth may trigger narcolepsy in genetically predisposed individuals. In this population-based case-control study, we sought to identify all prevalent cases of narcolepsy with cataplexy aged 18-50 years as of 1 July 2001, in King County, Washington. The 45 eligible cases who were DQB1*0602-positive were compared with 95 controls with this allele, identified through random-digit dialing and buccal smears. Cases and controls were interviewed in person about physician-diagnosed infectious and non-infectious illnesses, immunizations, head trauma and parasomnias or psychiatric problems during youth. Narcolepsy with cataplexy was more frequent in African-Americans and in poorer households. Adjusting for these factors, the condition was 5.4-fold more common [95% confidence interval (CI) = 1.5-19.1] among people reporting a physician-diagnosed strep throat before the age of 21 years. No other significant associations with childhood diseases, immunizations or head trauma were found. However, prevalence was increased 16.3-fold (95% CI = 6.1-44.1) in subjects who reported having had 'night terrors'. Strep throat may be related to narcolepsy with cataplexy in genetically susceptible individuals. The association with night terrors could simply reflect early symptoms of narcolepsy, or they could be a prodromal sign of disturbed sleep physiology.
    Journal of Sleep Research 09/2009; 19(1 Pt 1):80-6. · 3.04 Impact Factor
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    ABSTRACT: We tested 2655 Peruvian men who have sex with men for the presence of retroviral infection. Human T cell lymphotropic virus type 1 (HTLV-1) was detected in 48 (1.8%) of the patients, HTLV-2 was detected in 28 (1.1%), and HTLV-1 and HTLV-2 were both detected in 5 (0.2%). Human immunodeficiency virus infection was detected in 329 (12.4%) of the patients; 24 (7.3%) had HTLV coinfection. Risk factors for HTLV-1 and HTLV-2 infection varied with sexual role.
    Clinical Infectious Diseases 08/2009; 49(1):112-7. · 9.37 Impact Factor

Publication Stats

352 Citations
203.48 Total Impact Points

Institutions

  • 2007–2013
    • University of Washington Seattle
      • Department of Neurology
      Seattle, Washington, United States
  • 2012
    • Swedish Medical Center Seattle
      Seattle, Washington, United States
  • 2009–2011
    • Stanford University
      • Department of Neurology and Neurological Sciences
      Palo Alto, CA, United States