Biomedical subjects

Haibo Zhou

Publications and source records attributed to Haibo Zhou.

13 recordsLinked to original sources

PubMed2006

Personal coronary risk profiles modify autonomic nervous system responses to air pollution.

OBJECTIVE: We investigated whether PM2.5-mediated autonomic modulation depends on individual coronary risk profiles. METHODS: Five-minute average heart rate (HR) and heart rate variability (HRV, including standard deviation of normal-to-normal intervals [SDNN], square root of the mean squared differences of successive NN intervals [rMSSD], high frequency [HF]) were measured from 24-hour ambulatory electrocardiograms, and personal PM(2.5) exposures were monitored in a prospective study of 10 male boilermakers (aged 34.3 +/- 8.1 years). We used the Framingham score to classify individuals into low (score = 1-3) and high (score = 5-6) risk categories. Mixed-effect models were used for statistical analyses. RESULTS: Each 1-mg/m(3) increase in the preceding 4-hour moving average PM(2.5) was associated with HR increase (5.3 beats/min) and HRV reduction (11.7%, confidence interval [CI] = 6.2-17.1% for SDNN; 11.1%, CI = 3.1-19.1% for rMSSD; 16.6%, CI = 1.5-31.7% for HF). Greater responses (2- to 4-fold differences) were observed in high-risk subjects than in low-risk subjects. CONCLUSIONS: Our study suggests that adverse autonomic responses to metal particulate are aggravated in workers with higher coronary risk profiles.

Adult↗

PubMed2006

A semiparametric empirical likelihood method for biased sampling schemes with auxiliary covariates.

We consider a semiparametric inference procedure for data from epidemiologic studies conducted with a two-component sampling scheme where both a simple random sample and multiple outcome- or outcome-/auxiliary-dependent samples are observed. This sampling scheme allows the investigators to oversample certain subpopulations believed to have more information about the regression model while still gaining insights about the underlying population through the simple random sample. We focus on settings where there is no additional information about the parent cohort and the sampling probability is nonidentifiable. We motivate our problem with an ongoing study to assess the association between the mutation level of epidermal growth factor receptor (EGFR) and the antitumor response to EGFR-targeted therapy among nonsmall cell lung cancer patients. The proposed method applies to both binary and multicategorical outcome data and allows an arbitrary link function in the framework of generalized linear models. Simulation studies show that the proposed estimator has nice small sample properties. The proposed method is illustrated with a data example.

Analysis of Variance↗

PubMed2006

Statistical models for human fecundability.

Statistical models for fertility studies play a critical role in understanding the biology for conception and in identifying potential environmental factors that may negatively affect human reproduction. Aided with improved computing capability, statistical modeling for fertility data has made a remarkable progress in the past decade. The author provides an overview of the historic and current developments for fecundability models.

Fertility↗

PubMed2005

In utero exposure to background levels of polychlorinated biphenyls and cognitive functioning among school-age children.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental contaminants. In utero exposure to background levels of PCBs has been associated with intellectual impairment among children in most, but not all, studies. The authors evaluated prenatal PCB exposure in relation to cognitive test (intelligence quotient (IQ)) scores on the Wechsler Intelligence Scale for Children at age 7 years. Pregnant women were recruited from 12 US study centers from 1959 to 1965, and their children were followed until age 7 years (the Collaborative Perinatal Project). Third trimester serum was analyzed for PCBs in 1997-1999 for 732 women selected at random and for an additional 162 women whose children had either a low or a high IQ score. The PCB-IQ association was examined in multivariate models. Among those in the lowest exposure category (<1.25 microg of PCB/liter of serum), the fully adjusted mean IQ score was 93.6 (standard error: 1.8); among those in the highest category (> or =5 microg of PCB/liter), the mean IQ was 97.6 (standard error: 1.2); and overall the increase in IQ per unit increase in PCB level (microg/liter) was 0.22 (95% confidence interval: -0.28, 0.71). In these data, in utero exposure to background levels of PCBs was not associated with lower IQ at age 7 years.

Abnormalities, Drug-Induced↗

PubMed2005

Maternal serum level of the DDT metabolite DDE in relation to fetal loss in previous pregnancies.

Use of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) continues in about 25 countries. This use has been justified partly by the belief that it has no adverse consequences on human health. Evidence has been increasing, however, for adverse reproductive effects of DDT, but additional data are needed. Pregnant women who enrolled in the Collaborative Perinatal Project (United States, 1959-1965) were asked about their previous pregnancy history; blood samples were drawn and the serum frozen. In 1997-1999, the sera of 1717 of these women who had previous pregnancies were analyzed for 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), the major breakdown product of DDT. The odds of previous fetal loss was examined in relation to DDE level in logistic regression models. Compared with women whose DDE level was <15 microg/L, the adjusted odds ratios of fetal loss according to category of DDE were as follows: 15-29 microg/L, 1.1; 30-44 microg/L, 1.4; 45-59 microg/L, 1.6; and 60+ microg/L, 1.2. The adjusted odds ratio per 60 microg/L increase was 1.4 (95% confidence interval 1.1-1.6). The results were consistent with an adverse effect of DDE on fetal loss, but were inconclusive owing to the possibility that previous pregnancies ending in fetal loss decreased serum DDE levels less than did those carried to term.

Abortion, Spontaneous↗

PubMed2003

Prenatal exposure to low-level polychlorinated biphenyls in relation to mental and motor development at 8 months.

The relation between exposure to low levels of polychlorinated biphenyls (PCBs), a class of persistent organic pollutants, and cognitive and motor development in young children has been examined in several studies, and results have varied. The authors evaluated the association between prenatal exposure to PCBs and children's neurodevelopment using data from the Collaborative Perinatal Project. Pregnant women were enrolled from 1959 to 1965 from 12 sites across the United States. PCBs were measured in maternal serum taken during pregnancy. To measure children's mental and psychomotor development at 8 months of age, the authors administered the Bayley Scales of Infant Development (means, 87 (standard deviation, 15) and 88 (standard deviation, 18), respectively). Overall, they did not observe a relation between prenatal PCB exposure and children's mental or psychomotor scores (n = 1,207; multivariate adjusted beta = 0.1 point per micro g/liter increase of PCB, p = 0.71, and beta = 0.5, p = 0.14, respectively). The PCB-psychomotor score relation varied by study center (p < 0.05): The association was direct in some centers, inverse in others. This could not be attributed to variation in the timing or measurement of the child's neurodevelopment or analysis of PCBs because these were standardized across centers. The reasons for variation in results within this study and across other studies remain unclear.

Adult↗

PubMed2003

An unexpected distribution of sodium concentration in serum specimens stored for more than 30 years.

PURPOSE: Sera from over 50,000 pregnant women in the Collaborative Perinatal Project have been frozen at -20 degrees C since 1959 to 1966, and with the health data on their offspring constitute a resource that is still actively used. In two studies using these specimens, we measured sodium concentration to assess desiccation. METHODS: Sodium was measured in over 5,000 specimens by two different methods. For 10 specimens with unusually low sodium values, a substudy was done to investigate the cause. RESULTS: High sodium levels (>140 mmol/L) were present in more than 20% of specimens, and levels were unusually low (<130 mmol/L) in more than 40% of specimens. The substudy showed that filtering the specimens increased sodium levels and that about 14% of the sodium was trapped in particulate matter. CONCLUSIONS: High sodium levels in these specimens were probably due to desiccation and possibly to leaching of sodium from the glass containers. Low sodium levels were probably caused by the particulate matter, which clogged the analytical sampling devices and also trapped sodium. In serum specimens that have been stored for long periods, use of routine laboratory procedures for analysis can yield erroneous results. Furthermore, measured analyte levels can be affected by more than just degradation and desiccation.

Adult↗

PubMed2003

Estimating cycle pregnancy probability with incomplete data in contraceptive studies.

In studies on the effectiveness of barrier method contraceptives, researchers need to estimate the risk of pregnancy during consistent use of these methods. However, participants may not use assigned methods consistently, and only consistent-use cycles are included in the estimates. Inconsistent-use cycles are considered missing intervals, and a subject's early discontinuation from the study or pregnancy during inconsistent use is censored from the analysis. In this article, we consider a semiparametric maximum likelihood approach to estimate survival probability for grouped survival data with missing and censored data. The method is flexible in that it is nonparametric with respect to the underlying survival function, yet it can be easily extended to accommodate the covariates in a parametric way. Results from our simulation study show that the proposed method works well in practical sample sizes. Our findings support the U.S. Food and Drug Administration's (FDA) sample size requirements for contraceptive studies. We use data from an effectiveness trial on vaginal contraceptive film (VCF) to illustrate the proposed methods.

Clinical Trials as Topic↗

PubMed2002

Sleep duration, insomnia and behavioral problems among Chinese adolescents.

This study examined the associations among sleep duration, insomnia, and behavioral problems in a sample of 1359 Chinese adolescents. Participants completed a self-administrated questionnaire that included questions on sleep duration and insomnia symptoms and the Youth Self-Report of Child Behavior Checklist. It was found that adolescents who complained of insomnia reported sleep duration only half an hour shorter than did those without insomnia. Sleep duration did not differ among adolescents reporting three different types of insomnia (difficulty initiating sleep, difficulty maintaining sleep, and early morning awakening). Adolescents with insomnia reported more behavioral problems than did those without complaints of insomnia. After adjustment for age and sex, sleep duration of less than 7 h a day was significantly associated with most behavioral problems in those without complaints of insomnia but with only a few behavioral problems in adolescents reporting insomnia. Results suggest that sleep duration in adolescents with insomnia is short, but not as short as reported in previous clinical studies. Insomnia and short sleep duration are associated with a wide range of behavioral and emotional problems in adolescents.

Adolescent↗

PubMed2002

Maternal serum level of 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene and risk of cryptorchidism, hypospadias, and polythelia among male offspring.

1,1-Dichloro-2,2-bis(p-chlorophenyl)ethylene (p,p'-DDE) is a metabolite of the insecticide 2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane (DDT) and is a ubiquitous environmental contaminant. Nearly everyone in the United States has a detectable serum level of DDE. DDE was recently found to inhibit binding of androgen to its receptor and to block androgen action in rodents. Normal development of male genitalia in mammals depends on androgen action. The authors used stored serum samples to examine the relation between maternal DDE levels during pregnancy and adjusted odds of cryptorchidism (n = 219), hypospadias (n = 199), and polythelia (extra nipples) (n = 167) among male offspring, using a nested case-control design with one control group (n = 552). Subjects were selected from the Collaborative Perinatal Project, a US birth cohort study begun in 1959-1966, when DDE levels were much higher than they are at present. Compared with boys whose mother's recovery-adjusted serum DDE level was less than 21.4 microg/liter, boys with maternal levels greater than or equal to 85.6 microg/liter had adjusted odds ratios of 1.3 (95% confidence interval (CI): 0.7, 2.4) for crypt-orchidism, 1.2 (95% CI: 0.6, 2.4) for hypospadias, and 1.9 (95% CI: 0.9, 4.0) for polythelia. For cryptorchidism and polythelia, the results were consistent with a modest-to-moderate association, but in no instance was the estimate very precise. The results were inconclusive.

Adult↗

PubMed2002

Random effects logistic regression analysis with auxiliary covariates.

We study a semiparametric estimation method for the random effects logistic regression when there is auxiliary covariate information about the main exposure variable. We extend the semiparametric estimator of Pepe and Fleming (1991, Journal of the American Statistical Association 86, 108-113) to the random effects model using the best linear unbiased prediction approach of Henderson (1975, Biometrics 31, 423-448). The method can be used to handle the missing covariate or mismeasured covariate data problems in a variety of real applications. Simulation study results show that the proposed method outperforms the existing methods. We analyzed a data set from the Collaborative Perinatal Project using the proposed method and found that the use of DDT increases the risk of preterm births among U.S. children.

Biometry↗

PubMed2002

A semiparametric empirical likelihood method for data from an outcome-dependent sampling scheme with a continuous outcome.

Outcome-dependent sampling (ODS) schemes can be a cost effective way to enhance study efficiency. The case-control design has been widely used in epidemiologic studies. However, when the outcome is measured on a continuous scale, dichotomizing the outcome could lead to a loss of efficiency. Recent epidemiologic studies have used ODS sampling schemes where, in addition to an overall random sample, there are also a number of supplemental samples that are collected based on a continuous outcome variable. We consider a semiparametric empirical likelihood inference procedure in which the underlying distribution of covariates is treated as a nuisance parameter and is left unspecified. The proposed estimator has asymptotic normality properties. The likelihood ratio statistic using the semiparametric empirical likelihood function has Wilks-type properties in that, under the null, it follows a chi-square distribution asymptotically and is independent of the nuisance parameters. Our simulation results indicate that, for data obtained using an ODS design, the semiparametric empirical likelihood estimator is more efficient than conditional likelihood and probability weighted pseudolikelihood estimators and that ODS designs (along with the proposed estimator) can produce more efficient estimates than simple random sample designs of the same size. We apply the proposed method to analyze a data set from the Collaborative Perinatal Project (CPP), an ongoing environmental epidemiologic study, to assess the relationship between maternal polychlorinated biphenyl (PCB) level and children's IQ test performance.

Biometry↗

PubMedDate not supplied

In utero exposure to polychlorinated biphenyls and sensorineural hearing loss in 8-year-old children.

Early-life exposure to polychlorinated biphenyls (PCBs), a ubiquitous environmental contaminant, increases the hearing threshold at selected frequencies in rats. Among humans from the Faroe Islands with unusually high early-life PCB exposure, exposure was directly associated with increased hearing thresholds at two frequencies, although the deficits were present in the left ear but not the right. We examined PCB levels in maternal pregnancy serum in relation with audiometrically determined hearing thresholds among offspring when they were of school age. Complete data were available for 195 children with sensorineural hearing loss (SNHL) and 615 children selected at random, all of whom were born in 1959-1966 in the Collaborative Perinatal Project (CPP) U.S. cohort. The median exposure among those selected at random, as reflected by the mother's third trimester serum total PCB concentration, was 2.8 microg/l, about twofold higher than recent background levels in the United States. Based on the average hearing threshold across the frequencies essential for speech recognition in the "worst ear," the maternal serum PCB level was unrelated to the adjusted odds of SNHL or to adjusted mean hearing threshold. Overall, an adverse effect of early-life, background-level PCB exposure on SNHL was not supported by these data.

Adult↗