Prevalence of Staphylococcus aureus colonization among high-risk HIV populations

Staphylococcus aureus is a common microorganism in humans, typically colonizing the nasopharynx, skin and other mucosal surfaces. It is among the most frequent causes of clinically-significant bacterial infections accounting for increased morbidity and mortality among individuals with HIV/AIDS. Evidence of higher colonization rates among high-risk HIV populations have been observed however, prevalence estimates have varied. Additionally, behavioral, biological, and/or environmental factors that may account for these high colonization rates are not understood. Previous literature on clinic-based surveys were subject to considerable biases. Additionally, representative samples of high-risk HIV populations were difficult to obtain due in part to an underrepresentation of individuals who may not regularly obtain health care. ^ The main objective of this project is to determine the prevalence of methicillin-sensitive S. aureus (MSSA) and methicillin-resistant (MRSA) nasal colonization in two populations: 1) men who have sex with men (MSM) and 2) injection drug users (IDU). Both of these populations are included in the third round of the National HIV Behavioral Surveillance System (NHBS) in Houston, Texas. ^ In the NHBS-MSM3 study, logistic regression was used to report odds ratios and 95% confidence intervals (CI). For the NHBS-IDU3 study, to account for the lack of independence between samples, the method of generalized estimating equations was utilized to report adjusted odds ratios and 95% CI. The NHBS-MSM3 study enrolled 202 participants with a MSSA colonization rate of 26.7% and MRSA rate of 3%. In the NHBS-IDU3 study, 18.4% were nasally colonized with MSSA and 5.7% were nasally colonized with MRSA. Among the NHBS-MSM3 population, high-risk sexual practices were associated with colonization. For the NHBS-IDU3 population, age, marital status, employment status, and the presence of scabs, were associated with colonization status when controlling for size of recruitment network. In multivariate GEE analyses, the use of antiretroviral medications and age remained significantly associated with S. aureus nasal colonization when controlling for size of recruitment network and gender. In both studies, a significantly higher than expected S. aureus and MRSA colonization rate was observed as compared to colonization rates described for the general population. However, these estimates were moderate in comparison to reported clinic-based MSM and IDU S. aureus colonization findings. This study validates substantial prevalence differences and biases that may exist with data collected from clinic-based MSM and IDU. The prevalence of MSSA and MRSA nasal colonization did not differ significantly with respect to HIV status among NHBS-MSM3/NHBS-IDU3 participants. Continued examination on the effects of S. aureus colonization and infection should be examined longitudinally to confirm additional community-based determinants in populations that are disproportionately affected.^

Risk factors for surgical site infections among patients undergoing major colon surgery in the United States 2007-2009

Background: Surgical site infections (SSIs) after abdominal surgeries account for approximately 26% of all reported SSIs. The Center for Disease Control and Prevention (CDC) defines 3 types of SSIs: superficial incisional, deep incisional, and organ/space. Preventing SSIs has become a national focus. This dissertation assesses several associations with the individual types of SSI in patients that have undergone colon surgery. ^ Methods: Data for this dissertation was obtained from the American College of Surgeons' National Surgical Quality Improvement Program (NSQIP); major colon surgeries were identified in the database that occurred between the time period of 2007 and 2009. NSQIP data includes more than 50 preoperative and 30 intraoperative factors; 40 collected postoperative occurrences are based on a follow-up period of 30 days from surgery. Initially, four individual logistic regressions were modeled to compare the associations between risk factors and each of the SSI groups: superficial, deep, organ/space and a composite of any single SSI. A second analysis used polytomous regression to assess simultaneously the associations between risk factors and the different types of SSIs, as well as, formally test the different effect estimates of 13 common risk factors for SSIs. The final analysis explored the association between venous thromboembolism (VTEs) and the different types of SSIs and risk factors. ^ Results: A total of 59,365 colon surgeries were included in the study. Overall, 13% of colon cases developed a single type of SSI; 8% of these were superficial SSIs, 1.4% was deep SSIs, and 3.8% were organ/space SSIs. The first article identifies the unique set of risk factors associated with each of the 4 SSI models. Distinct risk factors for superficial SSIs included factors, such as alcohol, chronic obstructive pulmonary disease, dyspnea and diabetes. Organ/space SSIs were uniquely associated with disseminated cancer, preoperative dialysis, preoperative radiation treatment, bleeding disorder and prior surgery. Risk factors that were significant in all models had different effect estimates. The second article assesses 13 common SSI risk factors simultaneously across the 3 different types of SSIs using polytomous regression. Then each risk factor was formally tested for the effect heterogeneity exhibited. If the test was significant the final model would allow for the effect estimations for that risk factor to vary across each type of SSI; if the test was not significant, the effect estimate would remain constant across the types of SSIs using the aggregate SSI value. The third article explored the relationship of venous thromboembolism (VTE) and the individual types of SSIs and risk factors. The overall incidence of VTEs after the 59,365 colon cases was 2.4%. All 3 types of SSIs and several risk factors were independently associated with the development of VTEs. ^ Conclusions: Risk factors associated with each type of SSI were different in patients that have undergone colon surgery. Each model had a unique cluster of risk factors. Several risk factors, including increased BMI, duration of surgery, wound class, and laparoscopic approach, were significant across all 4 models but no statistical inferences can be made about their different effect estimates. These results suggest that aggregating SSIs may misattribute and hide true associations with risk factors. Using polytomous regression to assess multiple risk factors with the multiple types of SSI, this study was able to identify several risk factors that had significant effect heterogeneity across the 3 types of SSI challenging the use of aggregate SSI outcomes. The third article recognizes the strong association between VTEs and the 3 types of SSIs. Clinicians understand the difference between superficial, deep and organ/space SSIs. Our results indicate that they should be considered individually in future studies.^

Risk and protective factors associated with depression among racial and ethnic mothers of adolescents

The central paradigm linking disadvantaged social status and mental health has been the social stress model (Horwitz, 1999), the assumption being that individuals residing in lower social status groups are subjected to greater levels of stress not experienced by individuals from higher status groups. A further assumption is that such individuals have fewer resources to cope with stress, in turn leading to higher levels of psychological disorder, including depression (Pearlin, 1989). Despite these key assumptions, there is a dearth of literature comparing the social patterning of stress exposure (Hatch & Dohrenwend, 2007; Meyer, Schwartz, & Frost, 2008; Kessler, Mickelson, & Williams, 1999; Turner & Avison, 2003; Turner & Lloyd, 1999; Turner, Wheaton, & Lloyd, 1995), and the distribution and contribution of protective factors, posited to play a role in the low rates of depression found among African- and Latino-Americans (Alegria et al., 2007; Breslau, Aguilar-Gaxiola, Kendler, Su, Williams, & Kessler, 2006; Breslau, Borges, Hagar, Tancredi, Gilman, 2009; Gavin, Walton, Chae, Alegria, Jackson, & Takeuchi, 2010; Williams, & Neighbors, 2006). Thus, this study sought to describe both the distribution and contribution of risk and protective factors in relation to depression among a sample of African-, European-, and Latina-American mothers of adolescents, including testing a hypothesized mechanism through which social support, an important protective factor specific to women and depression, operates. ^ Despite the finding that the levels of depression were not statistically different across all three groups of women, surprising results were found in describing the distribution of both risk and protective factors, in that results reported among all women who were mothers when analyzed masked differences within each ethnic group when SES was assessed, a point made explicit by Williams (2002) regarding racial and ethnic variations in women's health. In the final analysis, while perceived social support was found to partially mediate the effect of social isolation on depression, among African-Americans, the direct effect of social isolation and depression was lower among this group of women, as was the indirect effect of social isolation and perceived social support when compared to European- and Latina-American mothers. Or, put differently, higher levels of social isolation were not found to be as associated with more depression or lower social support among African-American mothers when compared to their European- and Latina-American counterparts. ^ Women in American society occupy a number of roles, i.e., that of being female, married or single, mother, homemaker or employee. In addition, to these roles, ethnicity and SES also come into play, such that the intersection of all these roles and the social contexts that they occupy are equally important and must be taken into consideration when making predictions drawn from the social stress model. Based on these findings, it appears that the assumptions of the social stress model need to be revisited to include the variety of roles that intersect among individuals from differing social groups. More specifically, among women who are mothers and occupy a myriad of other roles, i.e., that of being female, married or single, African- or Latina-American, mother, homemaker or employee, the intersection of all the roles and the social contexts that women occupy are equally important and must be taken into consideration when looking at both the types and distribution of stressors across women. Predictions based on simple, mutually exclusive categories of social groups may lead to erroneous assumptions and misleading results.^

Colorectal cancer screening: Participation and determinants in West Texas

Early detection by screening is the key to colorectal cancer control. However, colorectal cancer screening and its determinants in rural areas have not been adequately studied. This goal of this study was to investigate the screening participation and determinants of colonoscopy, sigmoidoscopy, and/or fecal occult blood test (FOBT) in subjects of Project Frontier from the rural counties of Cochran, Bailey and Parmer, Texas. Subjects ( n=820 with 435 Hispanics, 355 Non-Hispanic Whites, 26 African Americans, and 4 unknown ethnicity; 255 males, 565 females, aged from 40 to 92 years) were from Project FRONTIER. Stepwise logistic regression analysis was performed. Explanatory variables included ethnicity (Hispanic, Non-Hispanic white and African American), gender, health insurance, smoking status, household income, education (years), physical activity, overweight, other health screenings, personal physicians, family history (first-degree relatives) of cancers, and preferred language (English vs. Spanish) for interview/testing. The screening percentage for ever having had a colonoscopy/sigmoidoscopy (51.8%) in this cohort aged 50 years or older is well below the percentage of the nation (65.2%) and Texas (64.6%) while the percentage for FOBT (29.2%) is higher than in the nation (17.2%) and Texas (14.9%). However, Hispanics had significantly lower participation than non-Hispanic whites for colonoscopy/sigmoidoscopy (37.0% vs. 66.0%) and FOBT (16.5% vs. 41.7%), respectively. Stepwise logistic regression showed that predictors for colonoscopy, sigmoidoscopy or FOBT included Hispanic race (p = 0.0045), age (p < 0.0001), other screening procedure (p < 0.0001), insurance status (p < 0.0001) and physician status (p = 0.0053). Screening percentage for colonoscopy/sigmoidoscopy in this rural cohort is well below the national and Texas level mainly due to the lower participation of Hispanics vs. Non-Hispanic whites. Health insurance, having had a personal physician, having had screenings for other cancers, race, and older age are among the main predictors.^

Comparison of machine learning approaches and statistical methods for estimation of airborne chemical exposures

Accurate quantitative estimation of exposure using retrospective data has been one of the most challenging tasks in the exposure assessment field. To improve these estimates, some models have been developed using published exposure databases with their corresponding exposure determinants. These models are designed to be applied to reported exposure determinants obtained from study subjects or exposure levels assigned by an industrial hygienist, so quantitative exposure estimates can be obtained. ^ In an effort to improve the prediction accuracy and generalizability of these models, and taking into account that the limitations encountered in previous studies might be due to limitations in the applicability of traditional statistical methods and concepts, the use of computer science- derived data analysis methods, predominantly machine learning approaches, were proposed and explored in this study. ^ The goal of this study was to develop a set of models using decision trees/ensemble and neural networks methods to predict occupational outcomes based on literature-derived databases, and compare, using cross-validation and data splitting techniques, the resulting prediction capacity to that of traditional regression models. Two cases were addressed: the categorical case, where the exposure level was measured as an exposure rating following the American Industrial Hygiene Association guidelines and the continuous case, where the result of the exposure is expressed as a concentration value. Previously developed literature-based exposure databases for 1,1,1 trichloroethane, methylene dichloride and, trichloroethylene were used. ^ When compared to regression estimations, results showed better accuracy of decision trees/ensemble techniques for the categorical case while neural networks were better for estimation of continuous exposure values. Overrepresentation of classes and overfitting were the main causes for poor neural network performance and accuracy. Estimations based on literature-based databases using machine learning techniques might provide an advantage when they are applied to other methodologies that combine `expert inputs' with current exposure measurements, like the Bayesian Decision Analysis tool. The use of machine learning techniques to more accurately estimate exposures from literature-based exposure databases might represent the starting point for the independence from the expert judgment.^

Predicting smokeless tobacco cessation in a blue -collar population

The use of smokeless tobacco products is undergoing an alarming resurgence in the United States. Several national surveys have reported a higher prevalence of use among those employed in blue-collar occupations. National objectives now target this group for health promotion programs which reduce the health risks associated with tobacco use.^ Drawn from a larger data set measuring health behaviors, this cross-sectional study tested the applicability of two related theories, the Theory of Reasoned Action (TRA) and the Theory of Planned Behavior (TPB), to smokeless tobacco (SLT) cessation in a blue-collar population of gas pipeline workers. In order to understand the determinants of SLT cessation, measures were obtained of demographic and normative characteristics of the population and specific constructs. Attitude toward the act of quitting (AACT) and subjective norm (SN) are constructs common to both models, perceived behavioral control (PBC) is unique to the TPB, and the number of past quit attempts is not contained in either model. In addition, a self-reported measure was taken of SLT use at two-month follow-up.^ The study population was comprised of all male SLT users who were field employees in a large gas pipeline company with gas compressor stations extending from Texas to the Canadian border. At baseline, 199 employees responded to the SLT portion of the survey, 118 completed some portion of the two-month follow-up, and 101 could be matched across time.^ As hypothesized, significant correlations were found between constructs antecedent to AACT and SN, although crossover effects occurred. Significant differences were found between SLT cessation intenders and non-intenders with regard to their personal and normative beliefs about quitting as well as their outcome expectancies and motivation to comply with others' beliefs. These differences occurred in the expected direction, with the mean intender score consistently higher than that of the non-intender.^ Contrary to hypothesis, AACT predicted intention to quit but SN did not. However, confirmatory of the TPB, PBC, operationalized as self-efficacy, independently contributed to the prediction of intention. Statistically significant relationships were not found between intention, perceived behavioral control, their interactive effects, and use behavior at two-month follow-up. The introduction of number of quit attempts into the logistic regression model resulted in insignificant findings for independent and interactive effects.^ The findings from this study are discussed in relation to their implications for program development and practice, especially within the worksite. In order to confirm and extend the findings of this investigation, recommendations for future research are also discussed. ^

Quality of life and functional status in a low -income, multiethnic HIV -positive population

The introduction of new medical treatments in recent years, commonly referred to as highly active antiretroviral therapy, has greatly increased the survival of patients with HIV/AIDS. As patients with HIV/AIDS continue to live longer, other important health-related outcomes, such as quality of life (QOL), should be thoroughly studied. There is also evidence that racial/ethnic minorities are disproportionately affected by HIV/AIDS, but potential health disparities among individuals already infected with HIV/AIDS have not been adequately examined in ethnically diverse populations. The purpose of this dissertation was to: (1) examine the impact of both demographic and behavioral variables on functional status and overall QOL among a population of ethnically diverse and economically disadvantaged HIV/AIDS patients; (2) examine the psychometric properties of a functional status measure—the Household and Leisure Time Activities questionnaire (HLTA); and (3) assess a proximal-distal theoretical framework for QOL using a full structural equation model in a population of patients with HIV/AIDS. Analyses were performed using data collected in the fall of 2000 from the project, Health and Work-Related Quality of Life and Health Risk Behaviors in a Multiethnic HIV-positive Population . Investigators from The University of Texas M.D. Anderson Cancer Center, The University of Texas-Houston Medical School, and The University of Texas School of Public Health conducted this project. The study site was the Thomas Street Clinic (TSC), a comprehensive HIV/AIDS care facility funded by the Harris County Hospital District (HCHD). TSC provides HIV/AIDS care to a diverse population of approximately 4000 medically indigent residents of Harris County. A systematic, consecutive sampling procedure yielded a sample size of 348 patients. Findings suggested that overall QOL, work-role functioning, household functioning, and leisure time functioning were impaired in this patient population. Results from the psychometric evaluation indicated that the HLTA was a reliable and valid measure of household and leisure time functioning status in a low-income multiethnic HIV-positive population. Finally, structural equation modeling of the proximal-distal QOL model suggested that this model was not a viable representation of the relationship between the study variables in this patient population. ^

Attitudes of health-care workers toward pregnant, HIV -positive women

The management of HIV infection with antiretroviral drugs has succeeded in increasing survival rates, but the subject of pregnancy in HIV-positive women continues to garner debate. Discrimination and stigma have been identified as barriers to health care, suggesting that women with HIV may be disinclined to seek prenatal care if health-care workers exhibit negative attitudes toward the women's pregnancies. To optimize prenatal and medical care for women with HIV infection, it is important to understand the general social conditions and cultural context in which these women have children. Goffman's treatise on stigma, Foucault's discussion of the knowledge/power matrix, and Bandura's Social Cognitive Theory offer theoretical perspectives by which we can evaluate the gender, race, and class issues that are inherent in pregnancy decision-making for women with HIV infection. It is also necessary to evaluate prevailing attitudes on childbearing toward HIV-positive women and to review the historical background of prejudice in which HIV-positive women make decisions regarding childbearing. ^ This qualitative study used a survey instrument and one-on-one interviews with HIV-infected women to elicit their perceptions of how they were treated by care providers when they became pregnant. It also included interviews with health-care workers to determine what their feelings are about pregnancy within the context of HIV infection. Results of the ethnographic inquiry reveal that most of the women had negative experiences at some point during a pregnancy, but that the situation improved when they sought care from a provider who was familiar with HIV infection. The health-care providers interviewed were firm in their belief that HIV-positive women deserved optimal care and treated the women with respect, but these are individuals who are also experts in providing care to HIV-positive patients. The question remains as to what kind of care HIV-positive women are receiving generally and what types of attitudes they are being subjected to if they see less experienced providers. Further research is also needed to determine whether HIV-positive women from a broader ethnic representation and higher socioeconomic status experience similar negative attitudes. ^

Efficacy of quality criteria to identify potentially harmful information: a cross-sectional survey of complementary and alternative medicine web sites.

BACKGROUND: Many users search the Internet for answers to health questions. Complementary and alternative medicine (CAM) is a particularly common search topic. Because many CAM therapies do not require a clinician's prescription, false or misleading CAM information may be more dangerous than information about traditional therapies. Many quality criteria have been suggested to filter out potentially harmful online health information. However, assessing the accuracy of CAM information is uniquely challenging since CAM is generally not supported by conventional literature. OBJECTIVE: The purpose of this study is to determine whether domain-independent technical quality criteria can identify potentially harmful online CAM content. METHODS: We analyzed 150 Web sites retrieved from a search for the three most popular herbs: ginseng, ginkgo and St. John's wort and their purported uses on the ten most commonly used search engines. The presence of technical quality criteria as well as potentially harmful statements (commissions) and vital information that should have been mentioned (omissions) was recorded. RESULTS: Thirty-eight sites (25%) contained statements that could lead to direct physical harm if acted upon. One hundred forty five sites (97%) had omitted information. We found no relationship between technical quality criteria and potentially harmful information. CONCLUSIONS: Current technical quality criteria do not identify potentially harmful CAM information online. Consumers should be warned to use other means of validation or to trust only known sites. Quality criteria that consider the uniqueness of CAM must be developed and validated.

The epidemiology of chronic fatigue in San Francisco

Chronic fatigue syndrome (CFS) is a recently defined condition characterized by severe disabling fatigue that persists for a minimum of six months, and a host of somatic and neurocognitive symptoms. Although conditions similar to CFS have been described in the medical literature for over 100 years, little is known about the epidemiology of CFS or of chronic fatigue generally. The San Francisco Fatigue Study was undertaken to describe the prevalence and characteristics of self-reported chronic fatigue and associated conditions in a diverse urban community. The study utilized a cross-sectional telephone survey of a random sample of households in San Francisco, followed by case/control interviews of fatigued and nonfatigued subjects. Respondents were classified as chronically fatigued (CF) if they reported severe fatigue lasting six months or longer, then further classified as having CFS-like illness if, based on self-reported information, their condition appeared to meet CFS case definition criteria. Subjects who reported idiopathic chronic fatigue that did not meet CFS criteria were classified as having ICF-like illness.^ 8004 households were screened, yielding fatigue and demographic information on 16970 residents. CF was reported by 635 persons, 3.7% of the study population. CFS-like illness was identified in 34 subjects (0.2%), and ICF-like illness in 259 subjects (1.6%). Logistic regression analysis indicated that prevalence odds ratios for CFS-like illness were significantly elevated for females compared to males (OR = 2.9), and in Blacks (OR = 2.9) and Native Americans (OR = 13.2) relative to Whites, but significantly lower in Asians (OR = 0.12). Above-average household income was protective for all categories of CF. CFS-like subjects reported more symptoms and were more severely disabled than ICF-like subjects, but the pattern of symptoms experienced by both groups was similar. In conclusion, unexplained chronic fatigue, including CFS-like illness, occurs in all sociodemographic groups, but may be most prevalent among persons with lower incomes and in some racial minorities. Future studies that include clinical evaluation of incident cases of CFS and ICF are required to further clarify the epidemiology of unexplained chronic fatigue in the population. ^

Nature and community in Western culture: Wendell Berry's alternative tradition

This dissertation is an examination of the ideals and practices that have characterized Western culture's relationship to the natural world. The conventional approach, depicted by some of the most prominent ecological publications of recent years, criticizes the Western tradition for both its ideals and practices. The ideals are assumed to be best represented in Western philosophy and religion and both of these sources have been indicted. These ideals are coupled with the Western way of life that is equally indicted as exploitive and destructive. Author, professor and farmer, Wendell Berry, offers an alternative to these indictments. Berry insists that a theme, advocating ecological accountability, runs through some of the West's most significant literature and that Western tradition contains a practice that can support these ecological principles. ^

Analyses of maternal and child mortality rates of five West African countries: Cote d'Ivoire, Guinea, Liberia, Senegal, Sierra Leone

After traveling to a small country in West Africa last summer, I became interested in learning more about the maternal, infant, and child death rates of that particular region of the continent. For the purposes of this paper I limited the number of countries that would be included in this research to five: Cote d'Ivoire, Guinea, Liberia, Senegal, and Sierra Leone. There are three hypotheses that were considered when conducting the research for this paper. The first was that there is no difference in the under five mortality rates for Cote d'Ivoire, Guinea, Liberia, Senegal, and Sierra Leone. The second hypothesis was that there is no difference in the female literacy rates for Cote d'Ivoire, Guinea, Liberia, Senegal, and Sierra Leone. The final hypothesis was that there is no difference in the male literacy rates for Cote d'Ivoire, Guinea, Liberia, Senegal, and Sierra Leone. The data used were collected from publicly available sources that include the CIA World Factbook, the WHO website, the UNICEF website, the Penn World Data table, and the World Bank website. The p-values that were calculated for all three hypotheses were found to be very significant, and all three of the null hypotheses were rejected. ^

Optimal frequency of Imiquimod (Aldara(RTM)) 5% cream treatment of external genital warts in immunocompetent adults. Systematic review and meta-analysis

Genital warts are a sexually transmitted disease with high prevalence in the U.S. Imiquimod 5% cream is a self-applied treatment, prescribed three-times weekly, at bedtime, for 16 weeks. The post-marketing research addressed questions of imiquimod dosing frequency. MEDLINE, Embase, and the Cochrane Library were searched for randomized trials on efficacy and safety of imiquimod 5% cream with either three-times weekly or once-daily regimens to systemically review treatment options. Efficacy was evaluated by completely cleared warts at the end of treatment, and safety - by frequency of adverse events and at least one rest period taken from treatment. Six studies were selected for the analysis, including circumcised men, uncircumcised men, and women. The once-daily compared to three-times weekly regimen did not improve the efficacy, but resulted in increased incidence of local skin reactions and events, when at least one rest period was taken from treatment. The optimal regimen is three-times weekly.^

Effects of health disparities on Helicobacter pylori infection among children on the US-Mexico border

The objective of this study is to determine whether health disparities influence the odds of developing H. pylori infections among the children enrolled in the Pasitos Cohort Study on the US-Mexico border. The study variables were the number of prenatal care visits, ways of transportation, car in household, location of health services and insurance coverage. The study recruited eligible pregnant women to complete baseline questionnaires. Every six months after the birth of the child, infection status is measure by the 13-C urea breath test. Results indicate that having medical insurance consistently decreases the odds of being infected. Children with mothers who went to a private physician had decreased odds of infection compared to those utilizing public clinics, and having a car in the household increased the odds of infection. Limitations include bias due to loss to follow-up and the transient nature of the infection.^

Phthalate exposure among US women, NHANES 1999--2002: Relationship to serum gonadotropin levels

Phthalates are industrial chemicals used primarily as plasticizers though they and are found in a myriad of consumer goods such as children's toys, food packaging, dental sealants, cosmetics, pharmaceuticals, perfumes, and building materials. US biomonitoring data show more than 75% of the population have exposure to mono-n-butyl phthalate (MBP), mono-ethyl phthalate (MEP), mono-(2-ethyl) hexyl phthalate (MEHP), and mono-benzyl phthalate (MBZP). Reproductive toxicity from phthalate exposure in animal models has raised concerns about similar effects on fertility in humans. This dissertation research focuses on phthalate exposures in the US population and investigates the plausibility of an exposure-response relationship between phthalates and endocrine hormones essential for ovulation among US women. The objective of this research is to determine the relationship between levels of gonadotropins, follicle stimulating hormone (FSH) and leutinizing hormone (LH), and urinary phthalate monoester metabolites: MBP, MEP, MEHP, MBZP among National Health and Nutrition Examination Survey (NHANES) 1999-2002 women aged 35 to 60 years. Using biomarker data from a one-third sub-sample of NHANES participants, log transformed serum FSH and serum LH, respectively were regressed on phthalates controlling for age, body mass index, smoking, and creatinine taking into consideration the complex survey design (n=385). Models were stratified by reproductive status: reproductive (n=185), menopause transition (n=49) and post-menopausal (n=125). A decrease in FSH associated with increasing MBzP (beta=-0.094, p<0.05) was observed for all participants but no statistical association between log FSH and MBP, MEP, or MEHP was seen. A decrease in LH (beta=-0.125, p<0.05) was also observed with increasing MBzP for all participants though there was no relationship between levels of LH and MBP, MEP, or MEHP. The observed associations between FSH, LH and MBzP did not persist when stratified by reproductive status. Thus, the present study shows a change in endocrine hormones related to ovulation with increasing urinary MBzP among a representative sample of US women from 1999-2002 though this observed exposure-response relationship does not remain after stratification by reproductive status. ^