An estimating equations approach to fitting latent exposure models with longitudinal health outcomes

The analysis of data arising from environmental health studies which collect a large number of measures of exposure can benefit from using latent variable models to summarize exposure information. However, difficulties with estimation of model parameters may arise since existing fitting procedures for linear latent variable models require correctly specified residual variance structures for unbiased estimation of regression parameters quantifying the association between (latent) exposure and health outcomes. We propose an estimating equations approach for latent exposure models with longitudinal health outcomes which is robust to misspecification of the outcome variance. We show that compared to maximum likelihood, the loss of efficiency of the proposed method is relatively small when the model is correctly specified. The proposed equations formalize the ad-hoc regression on factor scores procedure, and generalize regression calibration. We propose two weighting schemes for the equations, and compare their efficiency. We apply this method to a study of the effects of in-utero lead exposure on child development.Comment: Published in at http://dx.doi.org/10.1214/08-AOAS226 the Annals of Applied Statistics (http://www.imstat.org/aoas/) by the Institute of Mathematical Statistics (http://www.imstat.org

Estimators for longitudinal latent exposure models: examining measurement model assumptions

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136711/1/sim7268_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136711/2/sim7268.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136711/3/sim7268-sup-0001-Supplementary.pd

Hierarchical multiple informants models: examining food environment contributions to the childhood obesity epidemic

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/102625/1/sim5967.pd

Perinatal Lead (Pb) Exposure Results in Sex-Specific Effects on Food Intake, Fat, Weight, and Insulin Response across the Murine Life-Course

Developmental lead (Pb) exposure has been associated with lower body weight in human infants and late onset obesity in mice. We determined the association of perinatal Pb exposure in mice with changes in obesity-related phenotypes into adulthood. Mice underwent exposure via maternal drinking water supplemented with 0 (control), 2.1 (low), 16 (medium), or 32 (high) ppm Pb-acetate two weeks prior to mating through lactation. Offspring were phenotyped at ages 3, 6, and 9 months for energy expenditure, spontaneous activity, food intake, body weight, body composition, and at age 10 months for glucose tolerance. Data analyses were stratified by sex and adjusted for litter effects. Exposed females and males exhibited increased energy expenditure as compared to controls (p<0.0001 for both). In females, horizontal activity differed significantly from controls (p = 0.02) over the life-course. Overall, food intake increased in exposed females and males (p<0.0008 and p<0.0001, respectively) with significant linear trends at 9 months in females (p = 0.01) and 6 months in males (p<0.01). Body weight was significantly increased in males at the medium and high exposures (p = 0.001 and p = 0.006). Total body fat differed among exposed females and males (p<0.0001 and p<0.0001, respectively). Insulin response was significantly increased in medium exposure males (p<0.05). Perinatal Pb exposure at blood lead levels between 4.1 µg/dL and 32 µg/dL is associated with increased food intake, body weight, total body fat, energy expenditure, activity, and insulin response in mice. Physiological effects of developmental Pb exposure persist and vary according to sex and age

Estimating Co-Occurring Behavioral Trajectories Within a Neighborhood Context: A Case Study of Multivariate Transition Models for Clustered Data

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/63092/1/cerda_estimating co-occurring_2008.pd

Sleep‐disordered breathing and poststroke outcomes

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/150527/1/ana25515_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/150527/2/ana25515.pd

Exposure to Phthalates in Neonatal Intensive Care Unit Infants: Urinary Concentrations of Monoesters and Oxidative Metabolites

OBJECTIVE: We previously demonstrated that among 54 infants in neonatal intensive care units, exposure to polyvinyl chloride plastic medical devices containing the plasticizer di(2-ethylhexyl) phthalate (DEHP) is associated with urinary concentrations of mono(2-ethylhexyl) phthalate (MEHP), a DEHP metabolite. In this follow-up report, we studied the neonates’ exposure to DEHP-containing devices in relation to urinary concentrations of two other DEHP metabolites, and to urinary concentrations of metabolites of dibutyl phthalate (DBP) and benzylbutyl phthalate (BzBP), phthalates found in construction materials and personal care products. MEASUREMENTS: A priori, we classified the intensiveness of these 54 infants’ exposure to DEHP-containing medical products. We measured three metabolites of DEHP in infants’ urine: MEHP and two of its oxidative metabolites, mono(2-ethyl-5-hydroxylhexyl) phthalate (MEHHP) and mono(2-ethyl-5-oxohexyl) phthalate (MEOHP). We also measured monobutyl phthalate (MBP), a metabolite of DBP, and monobenzyl phthalate (MBzP), a metabolite of BzBP. RESULTS: Intensiveness of DEHP-containing product use was monotonically associated with all three DEHP metabolites. Urinary concentrations of MEHHP and MEOHP among infants in the high-DEHP-intensiveness group were 13–14 times the concentrations among infants in the low-intensiveness group (p ≤ 0.007). Concentrations of MBP were somewhat higher in the medium-and high-DEHP-intensiveness group; MBzP did not vary by product use group. Incorporating all phthalate data into a structural equation model confirmed the specific monotonic association between intensiveness of product use and biologic measures of DEHP. CONCLUSION: Inclusion of the oxidative metabolites MEHHP and MEOHP strengthened the association between intensiveness of product use and biologic indices of DEHP exposure over that observed with MEHP alone

Longitudinal Associations Between Neighborhood Recreational Facilities and Change in Recreational Physical Activity in the Multi-Ethnic Study of Atherosclerosis, 2000-2007

Many cross-sectional studies have investigated the relationship between neighborhood physical environment and physical activity. However, few studies have examined this relationship longitudinally, and no study has examined the association between change in objective measurements of physical activity resources and change in physical activity in adults. We used longitudinal data from the Multi-Ethnic Study of Atherosclerosis (2000–2007) of 6,814 adults who were aged 45–84 years at baseline. Physical activity was assessed via a semiquantitative questionnaire at baseline and at 2 follow-up visits (approximately 1.6 and 3.2 years later). We measured the density of recreational facilities within 1 mile of each participant's home address and used linear mixed-effects models to estimate the association between change in recreational facility density and change in physical activity. After adjusting for potential confounders, we found that a greater increase in recreational density was associated with a less pronounced decline in physical activity (mean difference in annual change in physical activity for each 1-unit increase in recreational density over time = 10.3 (95% confidence interval: 0.7, 19.9)). This association was stronger in older adults. Better access to recreational facilities may benefit middle-aged and older adults by enabling them to maintain activity levels as they age

Dietary patterns and diet quality during pregnancy and low birthweight: The PRINCESA cohort

Although the isolated effects of several specific nutrients have been examined, little is known about the relationship between overall maternal diet during pregnancy and fetal development and growth. This study evaluates the association between maternal diet and low birthweight (LBW) in 660 pregnant women from the Pregnancy Research on Inflammation, Nutrition,& City Environment: Systematic Analyses (PRINCESA) cohort in Mexico City. Using prior day dietary intake reported at multiple prenatal visits, diet was assessed prospectively using a priori (Maternal Diet Quality Score [MDQS]) and a posteriori (dietary patterns extracted by factor analysis) approaches. The association between maternal diet and LBW was investigated by logistic regression, controlling for confounders. Adherence to recommended guidelines (higher MDQS) was associated with a reduced risk of LBW (OR, 0.22; 95% confidence interval [0.06, 0.75], P < .05, N = 49) compared with the lowest adherence category (reference group), controlling for maternal age, education, height, marital status, pre- pregnancy body mass index, parity, energy intake, gestational weight gain, and preterm versus term birth; a posteriori dietary patterns were not associated with LBW risk. Higher adherence to MDQS was associated with a lower risk of having an LBW baby in this sample. Our results support the role of advocating a healthy overall diet, versus individual foods or nutrients, in preventing LBW.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155934/1/mcn12972_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155934/2/mcn12972.pd

An assessment of drinking water contamination with Helicobacter pylori in Lima, Peru

BackgroundHelicobacter pylori is a gut bacterium that is the primary cause of gastric cancer. H. pylori infection has been consistently associated with lack of access to sanitation and clean drinking water. In this study, we conducted time‐series sampling of drinking water in Lima, Peru, to examine trends of H. pylori contamination and other water characteristics.Materials and methodsDrinking water samples were collected from a single faucet in Lima’s Lince district 5 days per week from June 2015 to May 2016, and pH, temperature, free available chlorine, and conductivity were measured. Quantities of H. pylori in all water samples were measured using quantitative polymerase chain reaction. Relationships between the presence/absence and quantity of H. pylori and water characteristics in the 2015‐2016 period were examined using regression methods accounting for the time‐series design.ResultsForty‐nine of 241 (20.3%) of drinking water samples were contaminated with H. pylori. Statistical analyses identified no associations between sampling date and the likelihood of contamination with H. pylori. Statistically significant relationships were found between lower temperatures and a lower likelihood of the presence of H. pylori (P < .05), as well as between higher pH and higher quantities of H. pylori (P < .05).ConclusionsThis study has provided evidence of the presence of H. pylori DNA in the drinking water of a single drinking water faucet in the Lince district of Lima. However, no seasonal trends were observed. Further studies are needed to determine the presence of H. pylori in other drinking water sources in other districts in Lima, as well as to determine the viability of H. pylori in these water sources. Such studies would potentially allow for better understanding and estimates of the risk of infection due to exposure to H. pylori in drinking water.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/142894/1/hel12462.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/142894/2/hel12462_am.pd