Clustering Functional Data With Measurement Errors: A Simulation-Based Approach.

Clustering analysis of functional data, which comprises observations that evolve continuously over time or space, has gained increasing attention across various scientific disciplines. Practical applications often involve functional data that are contaminated with measurement errors arising from imprecise instruments, sampling errors, or other sources. These errors can significantly distort the inherent data structure, resulting in erroneous clustering outcomes.

Demand-driven capacity building for public health nutrition research in Lao PDR.

In Laos, rates of undernutrition, especially among children under 5 years of age, remain high. In response, a large multidisciplinary team embarked on a multi-year project in Laos beginning in 2019 with the purpose of institutional strengthening around public health nutrition research. This paper summarizes the Applied Nutrition Research Capacity Building project's activities, immediate project results, and prospects for sustaining impacts into the future.

A Cross-Sectional Study on the Association of Walnut Consumption with Obesity and Relative Fat Mass among United States Adolescents and Young Adults in NHANES (2003-2020).

Background: Walnuts contain nutrients and phytochemicals that can promote metabolic health. However, the high energy content of walnuts along with other nuts raises the concern that consuming nuts promotes obesity.

Objectives: We sought to investigate the associations between consumption of walnuts as well as other nuts and measures of obesity in adolescents and young adults.

Recommendations on statistical approaches to account for dose uncertainties in radiation epidemiologic risk models.

Purpose: Epidemiological studies of stochastic radiation health effects such as cancer, meant to estimate risks of the adverse effects as a function of radiation dose, depend largely on estimates of the radiation doses received by the exposed group under study. Those estimates are based on dosimetry that always has uncertainty, which often can be quite substantial. Studies that do not incorporate statistical methods to correct for dosimetric uncertainty may produce biased estimates of risk and incorrect confidence bounds on those estimates.

A Bayesian semi-parametric scalar-on-function regression with measurement error using instrumental variables.

Wearable devices such as the ActiGraph are now commonly used in research to monitor or track physical activity. This trend corresponds with the growing need to assess the relationships between physical activity and health outcomes, such as obesity, accurately. Device-based physical activity measures are best treated as functions when assessing their associations with scalar-valued outcomes such as body mass index.

Misstatements, misperceptions, and mistakes in controlling for covariates in observational research.

We discuss 12 misperceptions, misstatements, or mistakes concerning the use of covariates in observational or research. Additionally, we offer advice to help investigators, editors, reviewers, and readers make more informed decisions about conducting and interpreting research where the influence of covariates may be at issue. We primarily address misperceptions in the context of statistical management of the covariates through various forms of modeling, although we also emphasize design and model or variable selection.

Food insecurity and mental health among US adults during the COVID-19 pandemic: Results from National Health Interview Survey, 2020-2021.

Objective: To examine socio-demographic disparities in food insecurity during the COVID-19 pandemic and the association between food insecurity and mental health among US adults overall and communities vulnerable to food insecurity.

Methods: A cross-sectional study was conducted using the 2020-2021 National Health Interview Survey of 57,456 US adults. Weighted multivariable logistic regression models were used to estimate the association between food insecurity and anxiety or depression symptoms in overall US adults and subgroups including young adults (18-34 years), females, Hispanic people, non-Hispanic Black people, individuals with prior COVID-19 infection, the unemployed, low-income participants, participants with children, and Supplemental Nutrition Assistance Program (SNAP) participants.

A Dietary Model of Partial Meat Replacement with Walnuts Demonstrates Changes in the Nutrient Profile and Quality of the United States Population's Diet.

The purpose of the study is to assess the impact of partial meat replacement with walnuts using a dose-escalation approach on nutrient intake and diet quality in the usual US diet. Food modeling was implemented using the nationally representative 2015-2018 National Health and Examination Survey (NHANES), with a focus on non-nut consumers, which included 2707 children and adolescents and 5190 adults. Walnuts replaced meat in a dose-escalating manner (0.

Dietary supplementation with L-leucine reduces nitric oxide synthesis by endothelial cells of rats.

This study tested the hypothesis that elevated L-leucine concentrations in plasma reduce nitric oxide (NO) synthesis by endothelial cells (ECs) and affect adiposity in obese rats. Beginning at four weeks of age, male Sprague-Dawley rats were fed a casein-based low-fat (LF) or high-fat (HF) diet for 15 weeks. Thereafter, rats in the LF and HF groups were assigned randomly into one of two subgroups ( = 8/subgroup) and received drinking water containing either 1.

PARTIALLY FUNCTIONAL LINEAR QUANTILE REGRESSION WITH MEASUREMENT ERRORS.

Ignoring measurement errors in conventional regression analyses can lead to biased estimation and inference results. Reducing such bias is challenging when the error-prone covariate is a functional curve. In this paper, we propose a new corrected loss function for a partially functional linear quantile model with function-valued measurement errors.

Relationship between short-term self-reported dietary magnesium intake and whole blood ionized magnesium (iMg) or serum magnesium (s-Mg) concentrations.

Objective: Since we and others have shown that supplemental magnesium raises whole blood ionized magnesium (iMg) we investigated the relationships between self-reported dietary magnesium intake and concentrations of whole blood iMg and serum magnesium (s-Mg).

Methods: We obtained whole blood iMg concentrations, as well as s-Mg concentrations, from a pilot, three-arm, randomized, controlled, crossover bioavailability study of magnesium supplements ( = 23; 105 measures). Dietary magnesium intake was assessed using three-day food records and the Nutrition Data System for Research (NDSR, University of Minnesota, MN, USA).

Parametric and Semiparametric Approaches to Analyzing Device-Based Measures of Energy Expenditure in Zucker Diabetic Fatty Rats.

Background: Obesity results from a chronic imbalance between energy intake and energy expenditure. Total energy expenditure for all physiological functions combined can be measured approximately by calorimeters. These devices assess energy expenditure frequently (e.

Adding Walnuts to the Usual Diet Can Improve Diet Quality in the United States: Diet Modeling Study Based on NHANES 2015-2018.

Background: The under-consumption of calcium, potassium, fiber, and vitamin D is considered a U.S. public health concern.

A function-based approach to model the measurement error in wearable devices.

Physical activity (PA) is an important risk factor for many health outcomes. Wearable-devices such as accelerometers are increasingly used in biomedical studies to understand the associations between PA and health outcomes. Statistical analyses involving accelerometer data are challenging due to the following three characteristics: (i) high-dimensionality, (ii) temporal dependence, and (iii) measurement error.

Estimation of sparse functional quantile regression with measurement error: a SIMEX approach.

Quantile regression is a semiparametric method for modeling associations between variables. It is most helpful when the covariates have complex relationships with the location, scale, and shape of the outcome distribution. Despite the method's robustness to distributional assumptions and outliers in the outcome, regression quantiles may be biased in the presence of measurement error in the covariates.

Toward more rigorous and informative nutritional epidemiology: The rational space between dismissal and defense of the status quo.

To date, nutritional epidemiology has relied heavily on relatively weak methods including simple observational designs and substandard measurements. Despite low internal validity and other sources of bias, claims of causality are made commonly in this literature. Nutritional epidemiology investigations can be improved through greater scientific rigor and adherence to scientific reporting commensurate with research methods used.

Errors in the implementation, analysis, and reporting of randomization within obesity and nutrition research: a guide to their avoidance.

Randomization is an important tool used to establish causal inferences in studies designed to further our understanding of questions related to obesity and nutrition. To take advantage of the inferences afforded by randomization, scientific standards must be upheld during the planning, execution, analysis, and reporting of such studies. We discuss ten errors in randomized experiments from real-world examples from the literature and outline best practices for their avoidance.

Chlamydia trachomatis Is Associated With Medically Indicated Preterm Birth and Preeclampsia in Young Pregnant Women.

Background: Studies on Chlamydia trachomatis-associated pregnancy outcomes are largely conflicting, ignoring the heterogeneous natures of pregnancy complications and potential effect modification by maternal age. This study determined if prenatal C. trachomatis infection is associated with preterm birth (PTB) and preeclampsia subtypes.

Oral administration of α-ketoglutarate enhances nitric oxide synthesis by endothelial cells and whole-body insulin sensitivity in diet-induced obese rats.

Unlabelled: Obesity is a risk factor for many chronic diseases, including hypertension, type-2 diabetes, and cancer. Interestingly, concentrations of branched-chain amino acids (BCAAs) in plasma are commonly associated with endothelial dysfunction in humans and animals with obesity. Because L-leucine inhibits nitric oxide synthesis by endothelial cells (EC), we hypothesized that dietary supplementation with AKG (a substrate for BCAA transaminase) may stimulate BCAA catabolism in the small intestine and extra-intestinal tissues, thereby reducing the circulating concentrations of BCAAs and increasing nitric oxide synthesis by endothelial cells.

Instrumental variable approach to estimating the scalar-on-function regression model with measurement error with application to energy expenditure assessment in childhood obesity.

Wearable device technology allows continuous monitoring of biological markers and thereby enables study of time-dependent relationships. For example, in this paper, we are interested in the impact of daily energy expenditure over a period of time on subsequent progression toward obesity among children. Data from these devices appear as either sparsely or densely observed functional data and methods of functional regression are often used for their statistical analyses.

Illustration of Measurement Error Models for Reducing Bias in Nutrition and Obesity Research Using 2-D Body Composition Data.

Objective: This study aimed to illustrate the use and value of measurement error models for reducing bias when evaluating associations between body fat and having type 2 diabetes (T2D) or being physically active.

Methods: Logistic regression models were used to evaluate T2D and physical activity among adults aged 19 to 80 years from the Photobody Study (n = 558). Self-reported T2D and physical activity were categorized as "yes" or "no.

Identifying Syndemics for Sexually Transmitted Infections Among Young Adults in the United States: A Latent Class Analysis.

Purpose: Syndemic theory suggests that the convergence of social, environmental, and ecological factors can interact to exacerbate behavioral health problems and are often intensified by social conditions and disparities. This study used latent class analysis (LCA) to determine gender and racial/ethnic specific classes for sexually transmitted infection (STI) risk.

Methods: LCA included 18 measured socioeconomic, depression, substance use, and sexual behavioral variables from 1,664 young adults ages 18-25 in the NHANES.

Safety of dietary supplementation with arginine in adult humans.

Previous studies with animals and humans have shown beneficial effects of dietary supplementation with L-arginine (Arg) on reducing white fat and improving health. At present, a long-term safe level of Arg administration to adult humans is unknown. The objective of this study was to conduct a randomized, placebo-controlled, clinical trial to evaluate the safety and tolerability of oral Arg in overweight or obese but otherwise healthy adults with a body mass index of ≥ 25 kg/m.