Biomedical subjects

Paul J Rathouz

Publications and source records attributed to Paul J Rathouz.

At least 19 recordsLinked to original sources

PubMed2007

A missing data approach to semi-competing risks problems.

For event time data involving multiple mutually exclusive competing causes of failure, classic competing risks results show that marginal survival distributions are not identifiable. In a related instance, one or more failure modes may be observed provided that the failure events occur in a specific order. In such situations, sometimes referred to as semi-competing risks problems, the observations may under realistic assumptions lend information about parameters of interest that would be nonidentifiable in the strict competing risks case. Here, we present an approach that makes use of partially observable multiple modes of failures to obtain an estimate of the marginal distribution of one event type that may occur prior to the occurrence of another event type or be precluded by it. We apply the proposed method to the problem of estimating the distribution of time to tumour recurrence at specific sites among breast cancer patients participating in randomized clinical trials.

Antineoplastic Agents↗

PubMed2007

Maternal depression and early positive parenting predict future conduct problems in young children with attention-deficit/hyperactivity disorder.

Children with attention-deficit/hyperactivity disorder (ADHD) are at risk for adverse outcomes such as substance abuse and criminality, particularly if they develop conduct problems. Little is known about early predictors of the developmental course of conduct problems among children with ADHD, however. Parental psychopathology and parenting were assessed in 108 children who first met Diagnostic and Statistical Manual of Mental Disorders (4th ed.) criteria for ADHD at 4-7 years old. When demographic variables and baseline ADHD and conduct problems were controlled, maternal depression predicted conduct problems 2-8 years following the initial assessment, whereas positive parenting during the structured parent- child interaction task predicted fewer future conduct problems. These findings suggest that maternal depression is a risk factor, whereas early positive parenting is a protective factor, for the developmental course of conduct problems among children with ADHD.

Adaptation, Psychological↗

PubMed2007

Predictors of patient selection in bariatric surgery.

OBJECTIVE: To identify sociodemographic and clinical predictors of patient selection in bariatric surgery. SUMMARY BACKGROUND DATA: Population-based studies suggest that bariatric surgery patients are disproportionately privately insured, middle-aged white women. It is uncertain whether such disparities are due to surgeon decisions to operate, differences among morbidly obese individuals in access to surgery, or patients' personal preferences regarding surgical treatment. METHODS: We conducted a national survey of 1343 U.S. bariatric surgeons. The questionnaire contained clinical vignettes generated using a balanced fractional factorial design. For each of 3 hypothetical patients unique in age, race, gender, body mass index (BMI), comorbidities, social support, functional status, and insurance, respondents were asked if they would operate. Logistic regression was used to determine the odds of selection for each characteristic while controlling for the other 7 characteristics. Subset analyses were also performed using combinations of BMI and comorbidities. RESULTS: A total of 62.5% of eligible surgeons responded (n = 820). Patient race did not influence surgeon decisions to operate. Hypothetical patient age, BMI, and social support were most influential. In the subgroup of patients who did not meet current NIH BMI and comorbidity criteria for bariatric surgery, male sex (odds ratio [OR], 0.33; 95% confidence interval [CI], 0.14-0.76) was associated with decreased odds of selection. Overall, younger age (OR, 0.09; 95% CI, 0.07-0.11), older age (OR, 0.70; 95% CI, 0.56-0.90), limited functional status (OR, 0.66; 95% CI, 0.52-0.82), poor social support (OR, 0.37; 95% CI, 0.30-0.47), self-pay (OR, 0.72; 95% CI, 0.57-0.91), and public insurance (OR, 0.54; 95% CI, 0.43-0.67) were associated with decreased odds of selection. BMI and comorbidity criteria influenced the magnitude of these effects. CONCLUSIONS: Patient race did not play a role in surgeon decisions to operate. Further research should examine the roles of unequal access to bariatric surgery and differing socio-cultural perceptions of morbid obesity on racial disparities. The influence of patient age, gender, insurance status, social support, and functional status on decisions to operate was mitigated by BMI and comorbidities. Policy-makers currently debating BMI and comorbidity criteria for bariatric surgery should also consider guidelines pertaining to these sociodemographic issues that influence patient selection in bariatric surgery.

Adolescent↗

PubMed2006

Identifiability assumptions for missing covariate data in failure time regression models.

Methods in the literature for missing covariate data in survival models have relied on the missing at random (MAR) assumption to render regression parameters identifiable. MAR means that missingness can depend on the observed exit time, and whether or not that exit is a failure or a censoring event. By considering ways in which missingness of covariate X could depend on the true but possibly censored failure time T and the true censoring time C, we attempt to identify missingness mechanisms which would yield MAR data. We find that, under various reasonable assumptions about how missingness might depend on T and/or C, additional strong assumptions are needed to obtain MAR. We conclude that MAR is difficult to justify in practical applications. One exception arises when missingness is independent of T, and C is independent of the value of the missing X. As alternatives to MAR, we propose two new missingness assumptions. In one, the missingness depends on T but not on C; in the other, the situation is reversed. For each, we show that the failure time model is identifiable. When missingness is independent of T, we show that the naive complete record analysis will yield a consistent estimator of the failure time distribution. When missingness is independent of C, we develop a complete record likelihood function and a corresponding estimator for parametric failure time models. We propose analyses to evaluate the plausibility of either assumption in a particular data set, and illustrate the ideas using data from the literature on this problem.

Humans↗

PubMed2006

Objectively measured sleep characteristics among early-middle-aged adults: the CARDIA study.

Despite mounting evidence that sleep duration is a risk factor across diverse health and functional domains, little is known about the distribution and determinants of sleep. In 2003-2004, the authors used wrist activity monitoring and sleep logs to measure time in bed, sleep latency (time required to fall asleep), sleep duration, and sleep efficiency (percentage of time in bed spent sleeping) over 3 days for 669 participants at one of the four sites of the Coronary Artery Risk Development in Young Adults (CARDIA) study (Chicago, Illinois). Participants were aged 38-50 years, 58% were women, and 44% were Black. For the entire sample, mean time in bed was 7.5 (standard deviation (SD), 1.2) hours, mean sleep latency was 21.9 (SD, 29.0) minutes, mean sleep duration was 6.1 (SD, 1.2) hours, and mean sleep efficiency was 80.9 (SD, 11.3)%. All four parameters varied by race-sex group. Average sleep duration was 6.7 hours for White women, 6.1 hours for White men, 5.9 hours for Black women, and 5.1 hours for Black men. Race-sex differences (p < 0.001) remained after adjustment for socioeconomic, employment, household, and lifestyle factors and for apnea risk. Income was independently associated with sleep latency and efficiency. Sleep duration and quality, which have consequences for health, are strongly associated with race, sex, and socioeconomic status.

Adult↗

PubMed2006

Scale of interest versus scale of estimation: comparing alternative estimators for the incremental costs of a comorbidity.

We investigate how the scale of estimation in risk-adjustment models for health-care costs affects the covariate effect, where the scale of interest for the covariate effect may be different from the scale of estimation. As an illustrative example, we use claims data to estimate the incremental costs associated with heart failure within one year subsequent to myocardial infarction. Here, the scale of interest for the effect of heart failure on costs is additive. However, traditional methods for modeling costs use predetermined scale of estimation - for example, ordinary least squares (OLS) regression assumes an additive scale while log-transformed OLS and generalized linear models with log-link assume a multiplicative scale of estimation. We compare these models with a new flexible model that lets the data determine the appropriate scale of estimation. We use a variety of goodness-of-fit measures along with a modified Copas test to assess robustness, lack of fit, and over-fitting properties of the alternative estimators. Biases up to 19% in the scale of interest are observed due to the misrepresentation of the scale of estimation. The new flexible model is found to appropriately represent the scale of estimation and less susceptible to over-fitting despite estimating additional parameters in the link and the variance functions.

Bias↗

PubMed2006

Stability of the Pittsburgh Sleep Quality Index and the Epworth Sleepiness Questionnaires over 1 year in early middle-aged adults: the CARDIA study.

STUDY OBJECTIVES: To describe the stability of the Pittsburgh Sleep Quality Index (PSQI) and the Epworth Sleepiness Scale (ESS) scores over 1 year among a population-based sample of black and white early middle-aged adults. PARTICIPANTS: More than 600 participants, aged 38 to 50 years, from the Chicago site of the Coronary Artery Risk Development in Young Adults (CARDIA) Study. METHODS: The PSQI and ESS were completed twice, approximately 1 year apart, between 2003 and 2005. Seven PSQI 4-level component scores, a global PSQI score, and the ESS scores were calculated. A PSQI global score greater than 5 was classified as poor quality sleep, and an ESS score greater than 10 was classified as high daytime sleepiness. RESULTS: The mean+/-SD PSQI score was 5.7+/-3.1 in Year 1 and 5.9+/-3.1 in Year 2. The mean ESS score was 7.4+/-4.3 in Year 1 and 7.2+/-4.2 in Year 2. The Pearson correlation coefficient for the PSQI score in both years in the full sample was .68 and ranged from .54 among black men to .72 among black women. The Pearson correlation coefficient for the ESS score in both years in the full sample was .76 and ranged from .70 among black men to .80 among white men. In the full sample, 76% had the same PSQI dichotomous classification, and 85% had the same ESS dichotomous classification in both years. CONCLUSIONS: These results suggest that the PSQI and ESS are stable measures of sleep quality and sleepiness over the past year in early middle-aged adults.

Adult↗

PubMed2005

Family correlates of oppositional and conduct disorders in children with attention deficit/hyperactivity disorder.

Comorbidities among children with ADHD are key determinants of treatment response, course, and outcome. This study sought to separate family factors (parental psychopathology and parenting practices) associated with comorbid Oppositional Defiant Disorder (ODD) from those associated with Conduct Disorder (CD) among children with Attention Deficit/Hyperactivity Disorder. Clinic-referred families (n = 149) were diagnosed using DSM-IV criteria. Parents completed measures of parenting practices. Comorbid ODD and CD were significantly associated with maternal negative/ineffective discipline. Comorbid CD, but not ODD, was significantly associated with lack of maternal warmth and involvement, paternal negative/ineffective discipline, and with paternal Antisocial Personality Disorder (APD). However, the risk of CD posed by parenting appeared concentrated among children without a father having APD. While consistent discipline appears important for addressing comorbid ODD and CD, paternal psychopathology and the quality of the relationship between mother and child may pose risk specifically for comorbid CD. Efforts to prevent and/or treat CD should consider not only provision of structure and prudent discipline, but also the affective qualities of the relationship between the primary caretaker and child.

Attention Deficit Disorder with Hyperactivity↗

PubMed2005

Estimating marginal and incremental effects on health outcomes using flexible link and variance function models.

We propose an extension to the estimating equations in generalized linear models to estimate parameters in the link function and variance structure simultaneously with regression coefficients. Rather than focusing on the regression coefficients, the purpose of these models is inference about the mean of the outcome as a function of a set of covariates, and various functionals of the mean function used to measure the effects of the covariates. A commonly used functional in econometrics, referred to as the marginal effect, is the partial derivative of the mean function with respect to any covariate, averaged over the empirical distribution of covariates in the model. We define an analogous parameter for discrete covariates. The proposed estimation method not only helps to identify an appropriate link function and to suggest an underlying distribution for a specific application but also serves as a robust estimator when no specific distribution for the outcome measure can be identified. Using Monte Carlo simulations, we show that the resulting parameter estimators are consistent. The method is illustrated with an analysis of inpatient expenditure data from a study of hospitalists.

Adult↗

PubMed2005

Characteristics predicting nursing home admission in the program of all-inclusive care for elderly people.

PURPOSE: This study determined overall risk and predictors of long-term nursing home admission within the Program of All-Inclusive Care for the Elderly (PACE). DESIGN AND METHODS: DataPACE records for 4,646 participants aged 55 years or older who were enrolled in 12 Medicare- and Medicaid-capitated PACE programs during the period from June 1, 1990, to June 30, 1998, were obtained. Participants were enrolled for at least 30 days and had baseline evaluations within 30 days of enrollment. Cox proportional hazard models predicting an outcome of nursing home admission of 30 days or longer were estimated. RESULTS: The cumulative risk of admission to nursing homes for 30 days or longer was 14.9% within 3 years. Individuals enrolled from a nursing home were at very high risk for future admission, with a relative risk of 5.20 when compared with those living alone. Among individuals enrolled in PACE from the community, age, instrumental activity of daily living dependence, and bowel incontinence were predictive of subsequent nursing home admission. Asians and Blacks had a lower risk of institutionalization than Whites. However, other characteristics were not independently predictive of institutionalization, namely poor cognitive status, number of chronic conditions, activity of daily living deficits, urinary incontinence, several behavioral disturbances, and duration of program operation. Before adjusting for other variables, there was substantial site variability in risk of nursing home admission; this decreased considerably after other characteristics were adjusted for. IMPLICATIONS: Despite the fact that 100% of the PACE participants were nursing home certifiable, the risk of being admitted to a nursing home long term following enrollment from the community is low. The presence of some reversible risk factors may have implications for early intervention to reduce risk further, although the effect of these interventions is likely to be modest. Individuals who received long-term care in a nursing home prior to enrollment in PACE remain at high risk of readmission, despite the availability of comprehensive services.

Aged↗

PubMed2005

Self-reported smoking, cotinine levels, and patterns of smoking in pregnancy.

Non-pregnant adult smokers generally exhibit fairly stable smoking behaviour over time. In studies of this population, cotinine assays are considered a 'gold standard' measure of exposure to cigarette smoke; current smoking status can be validated with high sensitivity and specificity. In contrast, there is substantial within-person fluctuation in pregnancy smoking, as women try repeatedly to quit or cut down. As a result, cotinine measures may be of limited use for validation of amount smoked, as they are informative only about recent exposure, vary with individual smoking topography and are dependent on time lapsed since the last cigarette smoked. Thus, in reproductive epidemiology, where timing, intensity and duration of exposure are critical, self-reported history of cigarette consumption may be a more relevant fetal exposure than current smoking status. If there were substantial within-person variation over the course of pregnancy, numerous measures of cotinine would be needed to characterise patterns of fetal exposure and would not be feasible in many studies. We examined self-reported smoking patterns and compared them to patterns of urinary cotinine levels in a prospective study of 998 pregnant women, recruited 1988-92. Fluctuations in smoking were considerable and, while cotinine measures and self-reported number of cigarettes were highly correlated at any given time point across women (r=0.70), the within-person correlation between the patterns of self-reported number of cigarettes and cotinine levels was weaker (r=0.33). For researchers interested in fetal outcomes in which intensity and timing of exposure are critical, we conclude that self-reported variations in smoking during pregnancy may be a valid way to characterise detailed patterns of fetal exposure in epidemiological studies.

Adult↗

PubMed2005

Developmental transitions among affective and behavioral disorders in adolescent boys.

BACKGROUND: This paper expands upon recent efforts to advance beyond the examination of concurrent comorbidity between affective and behavioral disorders by testing developmental sequences among disorders. Doing so allows for improved tests of theories, such as Capaldi and Patterson's failure model of Conduct Disorder (CD) and depression. Furthermore, Oppositional Defiant Disorder (ODD) is rarely considered distinctly from CD, minimizing the ability to identify distinct effects among behavioral disorders. METHODS: This paper used data from the Developmental Trends Study, a clinic-referred cohort of 177 boys, along with their parents, who were assessed regularly using a structured clinical interview and a comprehensive set of other measures. Boys were recruited when they were between the ages of 7 and 12, and were reassessed annually until age 18. Predictive regression models tested the continuities among disorders, with depression, overanxious disorder, Attention Deficit Hyperactivity Disorder (ADHD), ODD and CD examined separately as outcomes. RESULTS: Each disorder showed homotypic continuity, but a clear developmental sequence of heterotypic continuity also emerged. ADHD was predicted by no other disorders, and exclusively predicted ODD. CD was predicted only by ODD. However, ODD was also directly predictive of future anxiety and depression, and anxiety predicted future depression as well. A specific test of the failure model of CD and depression supported that model. CONCLUSIONS: ODD appears as a pivotal developmental disorder in young males, in that ODD is notably influential in both subsequent behavioral and affective disorders. CD influences later depression only indirectly, through psychosocial impairment. Anxiety precedes depression, and ADHD is not predicted by other disorders.

Adolescent↗

PubMed2005

Limited English proficiency and breast and cervical cancer screening in a multiethnic population.

OBJECTIVES: We examined the relationship between ability to speak English and receipt of Papanicolaou tests, clinical breast examinations, and mammography in a multiethnic group of women in the United States. METHODS: We used longitudinal data from the Study of Women Across the Nation to examine receipt of breast and cervical cancer screening among Chinese, Japanese, Hispanic, and White women who reported reading and speaking (1) only a language other than English, (2) another language more fluently than English, or (3) only English or another language and English with equal fluency. Logistic regression was used to analyze the data. RESULTS: Reading and speaking only a language other than English and reading and speaking another language more fluently than English, were significantly and negatively associated with receipt of breast and cervical cancer screening in unadjusted models. Although these findings were attenuated in adjusted models, not speaking English well or at all remained negatively associated with receipt of cancer screening. CONCLUSIONS: These findings suggest that language barriers contribute to health disparities by impeding adequate health communication.

Acculturation↗

PubMed2004

The unintended impact of welfare reform on the medicaid enrollment of eligible immigrants.

BACKGROUND: During welfare reform, Congress passed legislation barring legal immigrants who entered the United States after August 1996 from Medicaid for five years after immigration. This legislation intended to bar only new immigrants (post-1996 immigrants) from Medicaid. However it may have also deterred the enrollment of legal immigrants who immigrated before 1996 (pre-1996 immigrants) and who should have remained Medicaid eligible. OBJECTIVES: To compare the Medicaid enrollment of U.S.-born citizens to pre-1996 immigrants, before and after welfare reform, and to determine if variation in state Medicaid policies toward post-1996 immigrants modified the effects of welfare reform on pre-1996 immigrants. DATA SOURCE/STUDY DESIGN: Secondary database analysis of cross-sectional data from 1994-2001 of the U.S. Census Bureau, Annual Demographic Survey of March Supplement of the Current Population Survey. SUBJECTS: Low-income, U.S.-born adults (N=116,307) and low-income pre-1996 immigrants (N=24,367) before and after welfare reform. MEASURES: Self-reported Medicaid enrollment. RESULTS: Before welfare reform, pre-1996 immigrants were less likely to enroll in Medicaid than the U.S.-born (OR=0.55; 95 percent CI, 0.51-0.59). After welfare reform, pre-1996 immigrants were even less likely to enroll in Medicaid. The proportion of immigrants in Medicaid dropped 3 percentage points after 1996; for the U.S.-born it dropped 1.6 percentage points (p=0.012). Except for California, state variation in Medicaid policy toward post-1996 immigrants did modify the effect of welfare reform on pre-1996 immigrants. CONCLUSIONS: Federal laws limiting the Medicaid eligibility of specific subgroups of immigrants appear to have had unintended consequences on Medicaid enrollment in the larger, still eligible immigrant community. Inclusive state policies may overcome this effect.

Adult↗

PubMed2003

Bootstrap calibration of TRANSMIT for informative missingness of parental genotype data.

Informative missingness of parental genotype data occurs when the genotype of a parent influences the probability of the parent's genotype data being observed. Informative missingness can occur in a number of plausible ways and can affect both the validity and power of procedures that assume the data are missing at random (MAR). We propose a bootstrap calibration of MAR procedures to account for informative missingness and apply our methodology to refine the approach implemented in the TRANSMIT program. We illustrate this approach by applying it to data on hypertensive probands and their parents who participated in the Framingham Heart Study.

Adult Children↗

PubMed2003

Alcohol advertising in magazines and adolescent readership.

CONTEXT: Adolescent drinking is a major public health concern. The federal government does not restrict alcohol advertising to adolescents, but relies on the alcohol industry for self-regulation. OBJECTIVES: To investigate recent alcohol advertising in magazines and to determine whether advertising frequency is associated with adolescent readership. DESIGN, SETTING, AND SUBJECTS: All alcohol advertisements were counted that appeared from 1997-2001 in 35 of 48 major US magazines, which tracked their adolescent readership (3 refused all alcohol advertisements; and advertisement counts were unavailable for 10). Variation was assessed in the advertisement placement frequency for each major category of alcohol (beer, wine and wine coolers, and distilled liquor) by a magazine's adolescent readership (age 12-19 years), young adult readership (age 20-24 years), and older adult readership (age > or =25 years); readership demographics (sex, race, and income); year; frequency of publication; and cost per advertisement. MAIN OUTCOME MEASURE: Variation in alcohol advertising frequency by adolescent readership. RESULTS: Adolescent readership ranged from 1.0 to 7.1 million. The alcohol industry placed 9148 advertisements at a cost of 696 million dollars. Of the 9148 advertisements, 1201 (13%) were for beer, 443 (5%) for wine, and 7504 (82%) for liquor. After adjustment for other magazine characteristics, the advertisement rate ratio was 1.6 times more for beer (95% confidence interval [CI], 1.0-2.6; P =.05) and liquor (95% CI, 1.1-2.3; P =.01) for every additional million adolescent readers. Wine industry advertising was not associated with adolescent readership. CONCLUSIONS: Magazine advertising by the beer and liquor industries is associated with adolescent readership. Industry and federal policymakers should examine ways to regulate advertising that reaches large numbers of adolescents.

Adolescent↗

PubMed2003

Informative missingness in genetic association studies: case-parent designs.

We consider the effect of informative missingness on association tests that use parental genotypes as controls and that allow for missing parental data. Parental data can be informatively missing when the probability of a parent being available for study is related to that parent's genotype; when this occurs, the distribution of genotypes among observed parents is not representative of the distribution of genotypes among the missing parents. Many previously proposed procedures that allow for missing parental data assume that these distributions are the same. We propose association tests that behave well when parental data are informatively missing, under the assumption that, for a given trio of paternal, maternal, and affected offspring genotypes, the genotypes of the parents and the sex of the missing parents, but not the genotype of the affected offspring, can affect parental missingness. (This same assumption is required for validity of an analysis that ignores incomplete parent-offspring trios.) We use simulations to compare our approach with previously proposed procedures, and we show that if even small amounts of informative missingness are not taken into account, they can have large, deleterious effects on the performance of tests.

Computer Simulation↗

PubMed2003

Does bone mineralization reflect economic conditions? An examination using a national US sample.

BACKGROUND: Bone density is the most important determinant of osteoporotic fractures, which lead to significant morbidity, disability and mortality for older persons, particularly women. Sensitive periods for bone mineralization in infancy, childhood and adolescence overlap with those for height attainment. After peak density is reached in early adulthood, there is age-related decline. We ask whether bone density, as height, reflects economic conditions. SUBJECTS AND METHODS: Using the third National Health and Nutrition Examination Survey, a probability sample of the US population which over-sampled Blacks and Mexican Americans, we examine the associations between adult bone mineral content (BMC) adjusted for bone and body size and three economic indicators: education, height and the poverty income ratio (PIR). We compare four groups: US-born Whites, Blacks and Mexican Americans and Mexican-born Mexican Americans. RESULTS: Education is positively associated with BMC only for White women, although there are similar, non-significant associations for Black women and White and Black men. For women, BMC is more strongly associated with height for Mexican Americans, especially the Mexican-born, than for Whites. For men, the only significant association is a negative one with education for men born in Mexico. PIR is not significantly associated with BMC, although there is pattern of lower income being associated with lower BMC for Whites and Blacks and higher BMC for Mexican Americans. CONCLUSION: Bone density does not reflect economic conditions as strongly or consistently as does physical stature. However, for women there is evidence that lower economic status in childhood or adolescence is associated with lower bone density.

Adolescent↗