Robust effect sizes and their confidence intervals for group difference between trajectories in hierarchical linear growth model

Hierarchical linear growth model (HLGM), as a flexible and powerful analytic method, has played an increased important role in psychology, public health and medical sciences in recent decades. Mostly, researchers who conduct HLGM are interested in the treatment effect on individual trajectories, which can be indicated by the cross-level interaction effects. However, the statistical hypothesis test for the effect of cross-level interaction in HLGM only show us whether there is a significant group difference in the average rate of change, rate of acceleration or higher polynomial effect; it fails to convey information about the magnitude of the difference between the group trajectories at specific time point. Thus, reporting and interpreting effect sizes have been increased emphases in HLGM in recent years, due to the limitations and increased criticisms for statistical hypothesis testing. However, most researchers fail to report these model-implied effect sizes for group trajectories comparison and their corresponding confidence intervals in HLGM analysis, since lack of appropriate and standard functions to estimate effect sizes associated with the model-implied difference between grouping trajectories in HLGM, and also lack of computing packages in the popular statistical software to automatically calculate them. ^ The present project is the first to establish the appropriate computing functions to assess the standard difference between grouping trajectories in HLGM. We proposed the two functions to estimate effect sizes on model-based grouping trajectories difference at specific time, we also suggested the robust effect sizes to reduce the bias of estimated effect sizes. Then, we applied the proposed functions to estimate the population effect sizes (d ) and robust effect sizes (du) on the cross-level interaction in HLGM by using the three simulated datasets, and also we compared the three methods of constructing confidence intervals around d and du recommended the best one for application. At the end, we constructed 95% confidence intervals with the suitable method for the effect sizes what we obtained with the three simulated datasets. ^ The effect sizes between grouping trajectories for the three simulated longitudinal datasets indicated that even though the statistical hypothesis test shows no significant difference between grouping trajectories, effect sizes between these grouping trajectories can still be large at some time points. Therefore, effect sizes between grouping trajectories in HLGM analysis provide us additional and meaningful information to assess group effect on individual trajectories. In addition, we also compared the three methods to construct 95% confident intervals around corresponding effect sizes in this project, which handled with the uncertainty of effect sizes to population parameter. We suggested the noncentral t-distribution based method when the assumptions held, and the bootstrap bias-corrected and accelerated method when the assumptions are not met.^

Exploring parental factors and their influence on early adolescent sexual health

Black and Hispanic youth experience the largest burden of sexually transmitted infections, teen pregnancy, and childbirth (Hamilton, Martin, & Ventura, 2011). Minority youth are disporportionately more likely to sexually debut at every age and debut before the age of 13 compared to whites (Centers for Disease Control and Prevention, 2011). However, there is little known about pre-coital sexual activity or protective parental factors in early adolscent minority youth. Parental factors such as parent-child communication and parental monitoring influence adolescent sexual behaviors and pre-coital sexual behaviors in early adolescence. Three distinct methods were used in this dissertation. Study one used qualitative methods, semi-structured, in-depth, individual interviews, to explore parent-child communication in African American mother-early adolescent son dyads. Study two used quantitative methods, secondary data analysis of a cross sectional study, to conduct a moderation analysis. For study three, I conducted a systematic review of parent-based adolescent sexual health interventions. Study one found that mothers feel comfortable talking about sex with adolescents, provide a two-prong sexual health message, and want their sons to tell their when they are thinking of having sex. Study found that parental monitoring moderates the relation between parent-child communication and pre-coital sexual behaviors. Study three found that interventions use a variety of theory, methods, and strategies and that no parent-based programs target faith-based organizations, mother-son or father-daughter dyads, or parents of LGBTQ youth. Adolescent sexual health interventions should consider addressing youth-to-parent disclosure of sexual activity or intentions to debut, addressing both parent-child sexual health communication and parental monitoring, and using a theoretical framework.^

Development and evaluation of a video-based modeling strategy for the dissemination phase of a school health tobacco -use prevention program

Even the best school health education programs will be unsuccessful if they are not disseminated effectively in a manner that encourages classroom adoption and implementation. This study involved two components: (1) the development of a videotape intervention to be used in the dissemination phase of a 4-year, NCI-funded diffusion study and (2) the evaluation of that videotape intervention strategy in comparison with a print (information transfer) strategy. Conceptualization has been guided by Social Learning Theory, Diffusion Theory, and communication theory. Additionally, the PRECEDE Framework has been used. Seventh and 8th grade classroom teachers from Spring Branch Independent School District in west Houston participated in the evaluation of the videotape and print interventions using a 57-item preadoption survey instrument developed by the UT Center for Health Promotion Research and Development. Two-way ANOVA was used to study individual score differences for five outcome variables: Total Scale Score (comprised of 57 predisposing, enabling, and reinforcing items), Adoption Characteristics Subscale, Attitude Toward Innovation Subscale, Receptivity Toward Innovation, and Reinforcement Subscale. The aim of the study is to compare the effect upon score differences of video and print interventions alone and in combination. Seventy-three 7th and 8th grade classroom teachers completed the study providing baseline and post-intervention measures on factors related to the adoption and implementation of tobacco-use prevention programs. Two-way ANOVA, in relation to the study questions, found significant scoring differences for those exposed to the videotape intervention alone for both the Attitude Toward Innovation Subscale and the Receptivity to Adopt Subscale. No significant results were found to suggest that print alone influences favorable scoring differences between baseline and post-intervention testing. One interaction effect was found suggesting video and print combined are more effective for influencing favorable scoring differences for the Reinforcement for the Adoption Subscale.^ This research is unique in that it represents a newly emerging field in health promotion communications research with implications for Social Learning Theory, Diffusion Theory, and communication science that are applicable to the development of improved school health interventions. ^

Age -period -cohort analysis: An extension of Cox's lifetable regression with time -dependent covariates

It is well known that an identification problem exists in the analysis of age-period-cohort data because of the relationship among the three factors (date of birth + age at death = date of death). There are numerous suggestions about how to analyze the data. No one solution has been satisfactory. The purpose of this study is to provide another analytic method by extending the Cox's lifetable regression model with time-dependent covariates. The new approach contains the following features: (1) It is based on the conditional maximum likelihood procedure using a proportional hazard function described by Cox (1972), treating the age factor as the underlying hazard to estimate the parameters for the cohort and period factors. (2) The model is flexible so that both the cohort and period factors can be treated as dummy or continuous variables, and the parameter estimations can be obtained for numerous combinations of variables as in a regression analysis. (3) The model is applicable even when the time period is unequally spaced.^ Two specific models are considered to illustrate the new approach and applied to the U.S. prostate cancer data. We find that there are significant differences between all cohorts and there is a significant period effect for both whites and nonwhites. The underlying hazard increases exponentially with age indicating that old people have much higher risk than young people. A log transformation of relative risk shows that the prostate cancer risk declined in recent cohorts for both models. However, prostate cancer risk declined 5 cohorts (25 years) earlier for whites than for nonwhites under the period factor model (0 0 0 1 1 1 1). These latter results are similar to the previous study by Holford (1983).^ The new approach offers a general method to analyze the age-period-cohort data without using any arbitrary constraint in the model. ^

Comparison of health behaviors of Mexican American and non -Hispanic White females: Implications for health promotion programs

Hispanics form the second-largest minority group in the United States totaling 22 million people. Health data on this population are sparse and inconsistent. This study seeks to determine use of preventative services and risk factor behaviors of Mexican American and non-Hispanic White females residing in South Texas.^ Baseline data from female respondents in household surveys in six South Texas counties (Ramirez and McAlister, 1988; McAlister et al., 1992) were analyzed to test the following hypotheses: (1) Mexican American and Non-Hispanic White females exhibit different patterns of health behaviors; (2) Mexican American females will exhibit different health behaviors regardless of age; and (3) the differences between Mexican American women and non-Hispanic White females are due to education and acculturation factors.^ Over the past decade, the traditional behaviors of Mexican American females have begun to change due to education, acculturation, and their participation in the labor force. The results from this study identify some of the changes that will require immediate attention from health care providers. Results revealed that regardless of ethnicity, age, education, and language preference, non-Hispanic White females were significantly more likely to participate in preventive screening practices than were Mexican American females. Risk factor analysis revealed a different pattern with Mexican American females significantly more likely to be non-smokers, non-alcoholic drinkers, and to have good fat avoidance practices compared to non-Hispanic White females. However, compared to those who are less-educated or Spanish-speaking, Mexican American females with higher levels of education and preference for speaking English only showed positive and negative health behaviors that were more similar to the non-Hispanic White females. The positive health behaviors that come with acculturation, e.g., more participation in preventive care and more physical activity, are welcome changes. But this study has implications for global health development and reinforces a need for "primordial" prevention strategies to deter the unwanted concomitants of economic development and acculturation. Smoking and drinking behaviors among Mexican American females need to be kept at low levels to prevent increased morbidity and premature deaths in this population. ^

Social integration, health behaviors and health status among Mexican-American women in the *southwestern United States

Using the Hispanic Health and Nutrition Examination Survey (HHANES), this research examined several health behaviors and the health status of Mexican American women. This study focused on determining the relative impact of social contextual factors: age, socioeconomic status, quality of life indicators, and urban/rural residence on (a) health behaviors (smoking, obesity and alcohol use) and (b) health status (physician's assessment of health status, subject's assessment of health status and blood pressure levels). In addition, social integration was analyzed. The social integration indicators relate to an individual's degree of integration within his/her social group: marital status, level of acculturation (a continuum of traditional Mexican ways to dominant U.S. cultural ways), status congruency, and employment status. Lastly, the social contextual factors and social integration indicators were examined to identify those factors that contribute most to understanding health behaviors and health status among Mexican American women.^ The study found that the social contextual factors and social integration indicators proved to be important concepts in understanding the health behaviors. Social integration, however, did not predict health status except in the case of the subject's assessment of health status. Age and obesity were the strongest predictors of blood pressure. The social contextual factors and obesity were significant predictors of the physician's assessment of health status while acculturation, education, alcohol use and obesity were significant predictors of the subject's assessment of health status. ^

The number and timing of time -dependent covariate measurements for the Cox regression model

The problem of analyzing data with updated measurements in the time-dependent proportional hazards model arises frequently in practice. One available option is to reduce the number of intervals (or updated measurements) to be included in the Cox regression model. We empirically investigated the bias of the estimator of the time-dependent covariate while varying the effect of failure rate, sample size, true values of the parameters and the number of intervals. We also evaluated how often a time-dependent covariate needs to be collected and assessed the effect of sample size and failure rate on the power of testing a time-dependent effect.^ A time-dependent proportional hazards model with two binary covariates was considered. The time axis was partitioned into k intervals. The baseline hazard was assumed to be 1 so that the failure times were exponentially distributed in the ith interval. A type II censoring model was adopted to characterize the failure rate. The factors of interest were sample size (500, 1000), type II censoring with failure rates of 0.05, 0.10, and 0.20, and three values for each of the non-time-dependent and time-dependent covariates (1/4,1/2,3/4).^ The mean of the bias of the estimator of the coefficient of the time-dependent covariate decreased as sample size and number of intervals increased whereas the mean of the bias increased as failure rate and true values of the covariates increased. The mean of the bias of the estimator of the coefficient was smallest when all of the updated measurements were used in the model compared with two models that used selected measurements of the time-dependent covariate. For the model that included all the measurements, the coverage rates of the estimator of the coefficient of the time-dependent covariate was in most cases 90% or more except when the failure rate was high (0.20). The power associated with testing a time-dependent effect was highest when all of the measurements of the time-dependent covariate were used. An example from the Systolic Hypertension in the Elderly Program Cooperative Research Group is presented. ^

A comparison of health behaviors of African -American male and female illicit drug users: Implications for community health practice

Prevalence of drug use, HIV, syphilis, and other STDs is particularly high in African-American populations. Although some studies have documented protective changes in health behaviors relevant to these outcomes, other research indicates that risky health behaviors are still widespread. Moreover, little is known about how African-American men and women have differed in their responses to calls to adopt protective behaviors. The study reported in this dissertation investigates gender differences in health risk behavior in a sample of 482 African American chronic, frequent injection drug and crack cocaine users residing in Houston, Texas. It uses baseline and 9 month follow-up data collected on this sample. Four major research questions are addressed. These questions are: Research question 1. What was the overall pattern of reduction in drug use for subjects in the sample? In particular, did subjects who reported a recent (30 day) reduction in drug use and needle sharing risk at baseline also report a reduction at follow-up? Research question 2. Is gender significantly associated with the overall pattern of risk reduction in drug injection observed in the two waves of the study? Research question 3. Is gender significantly associated with the overall pattern of reduction in the number of sexual partners observed in the two waves of the study? Research question 4. Is gender significantly associated with the overall pattern of increase in the use of barrier contraceptives in the two waves of the study? ^

Prevalence and risk factors of asthma and work -related asthma among U.S. adults: Data from the Third National Health and Nutrition Examination Survey, 1988--1994

This cross-sectional analysis of the data from the Third National Health and Nutrition Examination Survey was conducted to determine the prevalence and determinants of asthma and wheezing among US adults, and to identify the occupations and industries at high risk of developing work-related asthma and work-related wheezing. Separate logistic models were developed for physician-diagnosed asthma (MD asthma), wheezing in the previous 12 months (wheezing), work-related asthma and work-related wheezing. Major risk factors including demographic, socioeconomic, indoor air quality, allergy, and other characteristics were analyzed. The prevalence of lifetime MD asthma was 7.7% and the prevalence of wheezing was 17.2%. Mexican-Americans exhibited the lowest prevalence of MD asthma (4.8%; 95% confidence interval (CI): 4.2, 5.4) when compared to other race-ethnic groups. The prevalence of MD asthma or wheezing did not vary by gender. Multiple logistic regression analysis showed that Mexican-Americans were less likely to develop MD asthma (adjusted odds ratio (ORa) = 0.64, 95%CI: 0.45, 0.90) and wheezing (ORa = 0.55, 95%CI: 0.44, 0.69) when compared to non-Hispanic whites. Low education level, current and past smoking status, pet ownership, lifetime diagnosis of physician-diagnosed hay fever and obesity were all significantly associated with MD asthma and wheezing. No significant effect of indoor air pollutants on asthma and wheezing was observed in this study. The prevalence of work-related asthma was 3.70% (95%CI: 2.88, 4.52) and the prevalence of work-related wheezing was 11.46% (95%CI: 9.87, 13.05). The major occupations identified at risk of developing work-related asthma and wheezing were cleaners; farm and agriculture related occupations; entertainment related occupations; protective service occupations; construction; mechanics and repairers; textile; fabricators and assemblers; other transportation and material moving occupations; freight, stock and material movers; motor vehicle operators; and equipment cleaners. The population attributable risk for work-related asthma and wheeze were 26% and 27% respectively. The major industries identified at risk of work-related asthma and wheeze include entertainment related industry; agriculture, forestry and fishing; construction; electrical machinery; repair services; and lodging places. The population attributable risk for work-related asthma was 36.5% and work-related wheezing was 28.5% for industries. Asthma remains an important public health issue in the US and in the other regions of the world. ^

The association between academic achievement and health status among eighth -grade Hispanic students in Houston

This cross-sectional study examines the association between health and academic achievement among Hispanic eighth-grade students in the Houston Independent School District. As part of the district's 3 year Safe Schools/Healthy Students Initiative to enhance comprehensive educational programs, a brief anonymous questionnaire was administered in the classroom to 359 students in two schools during a one-month period in the early part of the 2001 school year. ^ The primary study questions are: Among this sample of Hispanic adolescents, is there a significant association between academic achievement and health status? and in this same population, is there a significant association between health risk behavior and health status? The specific aims of this research are: (1) to describe the association between academic achievement and health status; (2) to describe the association between health risk behaviors and health status; and (3) to describe the relative contribution of health risk behaviors and academic achievement to adolescent health status among this sample of Hispanic adolescents. ^ The survey instrument was a 32-item questionnaire that incorporated: several academic achievement questions measuring usual grades, school-related performance, attendance, student and perceived parental satisfaction with academic achievement, and educational aspirations; two health and quality of life scales measuring adolescent self-reported health; and specific measures of health risk behavior, e.g., frequency of tobacco cigarette smoking, alcohol and other drug use, aggression, and suicidal ideation and behavior that were incorporated from the national Youth Risk Behavior Survey. Questions pertaining to sexual behavior and pregnancy were omitted to comply with school district guidelines. ^ Analysis revealed that strong associations between academic achievement and health status and between health risk behaviors and health status were observed after controlling for the covariates. Eight factors were found to be significantly associated with poor health status: usual grades (low), academic performance (low), academic achievement beliefs (low), classroom and homework performance satisfaction (low), ever drinking alcohol (6 or more times), suicidality (ever thought about, planned for, or sought medical help after attempting suicide), gender (female), and age (15 years and older). (Abstract shortened by UMI.) ^

Analysis of interval -censored events in hypertension studies: Evaluation of treatment of coronary heart disease

Many statistical studies feature data with both exact-time and interval-censored events. While a number of methods currently exist to handle interval-censored events and multivariate exact-time events separately, few techniques exist to deal with their combination. This thesis develops a theoretical framework for analyzing a multivariate endpoint comprised of a single interval-censored event plus an arbitrary number of exact-time events. The approach fuses the exact-time events, modeled using the marginal method of Wei, Lin, and Weissfeld, with a piecewise-exponential interval-censored component. The resulting model incorporates more of the information in the data and also removes some of the biases associated with the exclusion of interval-censored events. A simulation study demonstrates that our approach produces reliable estimates for the model parameters and their variance-covariance matrix. As a real-world data example, we apply this technique to the Systolic Hypertension in the Elderly Program (SHEP) clinical trial, which features three correlated events: clinical non-fatal myocardial infarction, fatal myocardial infarction (two exact-time events), and silent myocardial infarction (one interval-censored event). ^

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. ^

Adverse Health Effects of Chronic Exposure to Low-Level Cadmium in Foodstuffs and Cigarette Smoke

Cadmium is a cumulative nephrotoxicant that is absorbed into the body from dietary sources and cigarette smoking. The levels of Cd in organs such as liver and kidney cortex increase with age because of the lack of an active biochemical process for its elimination coupled with renal reabsorption. Recent research has provided evidence linking Cd-related kidney dysfunction and decreases in bone mineral density in nonoccupationally exposed populations who showed no signs of nutritional deficiency. This challenges the previous view that the concurrent kidney and bone damage seen in Japanese itai-itai disease patients was the result of Cd toxicity in combination with nutritional deficiencies, notably, of zinc and calcium. Further, such Cd-linked bone and kidney toxicities were observed in people whose dietary Cd intakes were well within the provisional tolerable weekly intake (PTWI) set by the Joint Food and Agriculture Organization/World Health Organization Expert Committee on Food Additives of 1 mug/kg body weight/day or 70 mug/day. This evidence points to the much-needed revision of the current PTWI for Cd. Also, evidence for the carcinogenic risk of chronic Cd exposure is accumulating and Cd effects on reproductive outcomes have begun to emerge.

Health care utilization behavior of elders in a multicultural urban environment

The objective of this research is to determine the influences of social, environmental, behavioral, and economic forces on the health care service utilization of four racial/ethnic groups of non-institutionalized elders in a multicultural urban environment. To address these issues this dissertation examines three intertwined themes of culture, aging, and health, using a sample of elders residing in Miami-Dade County, FL in four racial/ethnic groups: white non-Hispanic; black non-Hispanic English speakers; Cuban; and non-Cuban Hispanic. ^ The research questions were analyzed using both quantitative and qualitative data. Data for the quantitative component uses telephone survey data from the Dade County Needs Assessment. The purpose of this component is to develop a more comprehensive model of elder health care utilization behavior. The qualitative component uses data from focus groups from Dade County Needs Assessment, archival data and a literature review of previous ethnographic research. The purpose of this component is to gain a better understanding of the social construction of the terms “age”' and “aging,” as well as to place issues of health and health care in the lives of elders. ^ The findings raised several important issues. First, just because people share a common chronological age does not mean that they are the same in every other respect. Examining elders as a homogeneous group of users of formal health care services in a community is simplistic. Placing “aging” and “health” in a cultural context is important. My findings confirm that the meaning of “aging” and “old” are socially constructed. Further, the term “aging” is NOT synonymous with ill health or frailty. This was a consistent finding in both the quantitative and qualitative results. ^ While all aging individuals share a mutual orientation toward aging (i.e., biological process), they do not age the same way (i.e., social construction of “aging”). Thus, policymakers and others serving the elder population must be aware of the particular cultural context, as well as the previous life experiences of the individuals that they serve. This analysis documents the importance of culture and geographic community in understanding health care service utilization of elders. ^

Health beliefs and health care options of disparate black communities in the United States

According to the 1999 U.S. Census, there were approximately thirty-three million African Americans and approximately 1.8 million non-Hispanic black immigrants in the United States. The 1997 U.S. Census estimated that there were as many as 554,000 foreign-born Haitians and 505,000 foreign-born Jamaicans living in the United States, mainly residing in Florida and New York. The U.S. Census claims that blacks are one of the largest emerging ethnic groups in America constituting at least twelve percent of this country's population. Because of this increase, their specific health beliefs and health care options are increasingly nationally significant. ^ In the present intra-black and inter-ethnic study, two hundred seventy African Americans, Haitian immigrants, and Jamaican immigrants residing in South Florida were quantitatively and qualitatively surveyed in order to investigate their health beliefs and health care options. According to the reviewed literature, the three black ethnic groups researched in this study have not been compared or contrasted before in relation to these beliefs and health care choices. ^ As was discovered by the present research, differing health beliefs and health care options were the cultural products of the ethnic differences of the researched communities. It was expected that differing health beliefs among the researched black groups might indicate disparate patterns of health care utilization of either western or non-western models. Additionally, it was projected that by investigating the health beliefs and the health care options of these emerging black ethnic groups, western health care providers in the United States could become better versed in medically servicing growing ethnically-disparate black populations. The study yielded results about the researched groups that supported major findings in the reviewed literature. The data were reported and examined, and theoretical generalizations from the data were discussed. The most important of these findings was that, within a race, health beliefs and health care options were determined by specific ethno-cultural variables dependent on national origins. ^