National Health and Nutrition Examination Survey, 2015-2018: Sample Design and Estimation Procedures.

Background The purpose of the National Health and Nutrition Examination Survey (NHANES) is to produce national estimates representative of the total noninstitutionalized civilian U.S. population. The sample for NHANES is selected using a complex, four-stage sample design. NHANES sample weights are used by analysts to produce estimates of the health-related statistics that would have been obtained if the entire sampling frame (i.e., the noninstitutionalized civilian U.S. population) had been surveyed. Sampling errors should be calculated for all survey estimates to aid in determining their statistical reliability. For complex sample surveys, exact mathematical formulas for variance estimates that fully incorporate the sample design are usually not available. Variance approximation procedures are required to provide reasonable, approximately unbiased, and design-consistent estimates of variance. Objective This report describes the NHANES 2015-2018 sample design and the methods used to create sample weights and variance units for the public-use data files, including sample weights for selected subsamples, such as the fasting subsample. The impacts of sample design changes on estimation for NHANES 2015-2018 are described. Approaches that data users can use to modify sample weights when combining survey cycles or when combining subsamples are also included.

An Investigation of Nonresponse Bias and Survey Location Variability in the 2017-2018 National Health and Nutrition Examination Survey.

Over the past two decades, a steady decline in response rates on national face-to-face surveys has been documented, with steeper declines observed in recent years. The impact of nonresponse on survey estimates is inconsistent and depends on the correlation between response propensity and the survey estimates. To better understand the impact of declining response rates on the 2017-2018 National Health and Nutrition Examination Survey (NHANES), potential nonresponse bias (NRB) was investigated. NRB was assessed using three approaches: (a) studying variation within the respondent set; (b) benchmarking and comparisons to external data; and (c) comparing alternative weighting adjustments. Because NHANES only samples 30 counties in every 2-year cycle, the sample of counties in any given cycle may be an outlier on some characteristics. Such sampling variability may compound the effects of NRB. For this reason, the representativeness of the 2017-2018 NHANES counties was examined by comparing: (a) the characteristics of the 2017-2018 sampled counties with those from prior cycles; (b) each sampled county with the average of all the counties in the sampling stratum from which that county was selected; and (c) the 2017-2018 counties with 5,000 other samples that could have been drawn under the same sample design using a simulation study. The NRB analyses showed that the 2017-2018 NHANES sample had a lower proportion of college graduates and higher-income individuals compared with prior cycles. Additionally, the 2017-2018 NHANES counties had lower proportions of college graduates and lower mean incomes compared with counties from prior cycles and counties not selected in 2017-2018, which exacerbated the effects of NRB. Weighting adjustments used in prior cycles were not sufficient to address the bias in the 2017-2018 NHANES. Instead, enhanced weighting adjustments for education and income reduced the bias resulting from nonresponse and location sampling variability.

Prevalence and Correlates of Receiving Medical Advice to Increase Physical Activity in U.S. Adults: National Health and Nutrition Examination Survey 2013-2016.

INTRODUCTION: National objectives recommend healthcare professionals provide physical activity advice. This study examined health and demographic characteristics associated with receipt of medical advice to increase physical activity among U.S. health care-utilizing adults and differences in associations by age group. METHODS: Analyses included 8,410 health care-utilizing adults aged ≥20 years from the 2013-2016 National Health and Nutrition Examination Surveys (analyzed in 2018). Logistic regression was used to examine associations between receipt of medical advice to increase physical activity in the past year and measured health conditions, reported health behaviors, and demographic characteristics. Models were stratified by age group (20-39, 40-59, and ≥60 years). RESULTS: Physical activity medical advice was received by 42.9% (95% CI=40.8, 44.9) of adults overall. By age group, 32.7% of younger adults, 46.7% of middle-aged adults, and 48.9% of older adults received advice. Among all adults and across all age groups, receipt of advice was higher among adults with chronic health conditions: obesity (63.0%, 95% CI=60.3, 65.7), hypertension (56.5%, 95%=CI 53.8, 59.2), diabetes (69.8%, 95% CI=66.5, 72.8), hypercholesterolemia (55.6%, 95% CI=52.3, 59.0), and low high-density lipoprotein cholesterol (53.8%, 95% CI=50.1, 57.4). Among all adults, those with obesity, hypertension, and diabetes had significantly greater odds of receipt of advice after adjustment. Stronger associations between diabetes and hypercholesterolemia and receiving physical activity advice were observed among younger adults. CONCLUSIONS: Receipt of physical activity medical advice was highest among adults with specific chronic health conditions, and this pattern was stronger among younger adults with diabetes and hypercholesterolemia. However, most health care-utilizing adults did not receive physical activity medical advice.

Trends in active transportation and associations with cardiovascular disease risk factors among U.S. adults, 2007-2016.

Active transportation (AT), or walking or bicycling for transportation, represents one way individuals can achieve recommended physical activity (PA) levels. This study describes AT prevalence and temporal trends, and examines associations between AT levels and measured CVD risk factors (hypertension, hypercholesterolemia, low high-density [HDL] cholesterol, diabetes, and obesity) among U.S. adults. National Health and Nutrition Examination Survey (NHANES) 2007-2016 data (analyzed in 2017) were used to conduct overall trend analyses of reported AT in a typical week [none (0-9 min/week); low (10-149 min/week); or high (≥150 min/week)]. Logistic regression was used to examine associations between AT level and each CVD risk factor from NHANES 2011-2016 (n = 13,943). Covariates included age, sex, race/Hispanic origin, education, income, smoking, survey cycle, non-transportation PA, and urbanization level. U.S. adults who engaged in high AT levels increased from 13.1% in 2007-2008 to 17.9% in 2011-2012, and then decreased to 10.6% in 2015-2016 (p for quadratic trend = 0.004). Over the same period, the quadratic trend for low AT was not significant. During 2011-2016, 14.3% of adults engaged in high AT, 11.4% in low AT, and 74.4% in no AT. High AT levels were associated with decreased odds of each CVD risk factor assessed, compared to no AT. Low AT (versus no AT) was associated with decreased odds of hypertension (aOR = 0.77, 95% CI 0.64, 0.91) and diabetes (aOR = 0.68, 95% CI 0.54, 0.85). AT prevalence among adults has fluctuated from 2007 to 2016. Despite favorable associations between AT and CVD risk factors, most U.S. adults do not engage in any AT.

Contribution of weight status to asthma prevalence racial disparities, 2-19 year olds, 1988-2014.

PURPOSE: Racial disparities in childhood asthma prevalence increased after the 1990s. Obesity, which also varies by race/ethnicity, is an asthma risk factor but its contribution to asthma prevalence disparities is unknown. METHODS: We analyzed nationally representative National Health Examination and Nutrition Survey data for 2-19 year olds with logistic regression and decomposition analyses to assess the contributions of weight status to racial disparities in asthma prevalence, controlling for sex, age, and income status. RESULTS: From 1988-1994 to 2011-2014, asthma prevalence increased more among non-Hispanic black (NHB) (8.4% to 18.0%) than non-Hispanic white (NHW) youth (7.2% to 10.3%). Logistic regression showed that obesity was an asthma risk factor for all groups but that a three-way "weight status-race/ethnicity-time" interaction was not significant. That is, weight status did not modify the race/ethnicity association with asthma over time. In decomposition analyses, weight status had a small contribution to NHB/NHW asthma prevalence disparities but most of the disparity remained unexplained by weight status or other asthma risk factors (sex, age and income status). CONCLUSIONS: NHB youth had a greater asthma prevalence increase from 1988-1994 to 2011-2014 than NHW youth. Most of the racial disparity in asthma prevalence remained unexplained after considering weight status and other characteristics.

Implementation of a Computerized Tablet-Survey in an Adolescent Large-Scale, School-Based Study.

BACKGROUND: Computerized surveys present many advantages over paper surveys. However, school-based adolescent research questionnaires still mainly rely on paper-and-pencil surveys as access to computers in schools is often not practical. Tablet-assisted self-interviews (TASI) present a possible solution, but their use is largely untested. This paper presents a method for and our experiences with implementing a TASI in a school setting. METHODS: A TASI was administered to 3907 middle and high school students from 79 schools. The survey assessed use of tobacco products and exposure to tobacco marketing. To assess in-depth tobacco use behaviors, the TASI employed extensive skip patterns to reduce the number of not-applicable questions that nontobacco users received. Pictures were added to help respondents identify the tobacco products they were being queried about. RESULTS: Students were receptive to the tablets and required no instructions in their use. None were lost, stolen, or broken. Item nonresponse, unanswered questions, was a pre-administration concern; however, 92% of participants answered 96% or more of the questions. CONCLUSIONS: This method was feasible and successful among a diverse population of students and schools. It generated a unique dataset of in-depth tobacco use behaviors that would not have been possible through a paper-and-pencil survey.

Prevalence of Low High-density Lipoprotein Cholesterol Among Adults, by Physical Activity: United States, 2011-2014.

KEY FINDINGS: Data from the National Health and Nutrition Examination Survey •The prevalence of low high-density lipoprotein (HDL) cholesterol was significantly higher among adults who did not meet recommended physical activity guidelines (21.0%) than adults who met the guidelines (17.7%). •Low HDL cholesterol prevalence differed significantly for both men and women by adherence to physical activity guidelines. •Prevalence of low HDL cholesterol declined as age increased for both those who did and did not meet the physical activity guidelines. •Non-Hispanic white and non-Hispanic black adults who did not meet the physical activity guidelines had a higher prevalence than those who met the guidelines. •Low HDL cholesterol prevalence declined with increasing education level regardless of adherence to physical activity guidelines. Regular physical activity can improve cholesterol levels among adults, including increasing high-density lipoprotein (HDL) cholesterol (1). HDL cholesterol is known as "good" cholesterol because high levels can reduce cardiovascular disease risk (2). The 2008 Physical Activity Guidelines for Americans recommend that adults engage in 150 minutes or more of moderate-intensity aerobic activity per week, 75 minutes of vigorous-intensity aerobic activity per week, or an equivalent combination (3). Adherence to these guidelines is expected to decrease the prevalence of low HDL cholesterol levels (4-8). This report presents national data for 2011-2014 on low HDL cholesterol prevalence among U.S. adults aged 20 and over, by whether they met these guidelines.

Trends in Anthropometric Measures Among US Children 6 to 23 Months, 1976-2014.

BACKGROUND AND OBJECTIVES: The surveillance of children's growth reflects a population's nutritional status and risk for adverse outcomes. This study aimed to describe trends in length-for-age, weight-for-age, weight-for-length, and early childhood weight gain among US children aged 6 to 23 months. METHODS: We analyzed NHANES data from 1976-1980, 1988-1994, 1999-2002, 2003-2006, 2007-2010, and 2011-2014. We estimated z scores < -2 (low) and ≥+2 (high) in comparison with World Health Organization growth standards for each indicator. Weight gain (relative to sex-age-specific medians) from birth until survey participation was estimated. Trends were assessed by low birth weight status and race/Hispanic origin. Race/Hispanic origin trends were assessed from 1988-1994 to 2011-2014. RESULTS: In 2011-2014, the prevalence of low and high length-for-age was 3.3% (SE, 0.8) and 3.7% (SE, 0.8); weight-for-age was 0.6% (SE, 0.3) and 7.0% (SE, 1.1); and weight-for-length was 1.0% (SE, 0.4) and 7.7% (SE, 1.2). The only significant trend was a decrease in high length-for-age (5.5% in 1976-1980 vs 3.7% in 2011-2014; P = .04). Relative weight gain between birth and survey participation did not differ over time, although trends differed by race/Hispanic origin. Non-Hispanic black children gained more weight between birth and survey participation in 2011-2014 versus 1988-1994, versus no change among other groups. CONCLUSIONS: Between 1976-1980 and 2011-2014, there were no significant trends in low or high weight-for-age and weight-for-length among 6- to 23-month-old children whereas the percent with high length-for-age decreased. A significant trend in relative weight gain between birth and survey participation was observed among non-Hispanic black children.

Blood Lead and Other Metal Biomarkers as Risk Factors for Cardiovascular Disease Mortality.

Analyses of the Third National Health and Nutrition Examination Survey (NHANES III) in 1988 to 1994 found an association of increasing blood lead levels < 10 µg/dL with a higher risk of cardiovascular disease (CVD) mortality. The potential need to correct blood lead for hematocrit/hemoglobin and adjust for biomarkers for other metals, for example, cadmium and iron, had not been addressed in the previous NHANES III-based studies on blood lead-CVD mortality association. We analyzed 1999 to 2010 NHANES data for 18,602 participants who had a blood lead measurement, were ≥ 40 years of age at the baseline examination and were followed for mortality through 2011. We calculated the relative risk for CVD mortality as a function of hemoglobin- or hematocrit-corrected log-transformed blood lead through Cox proportional hazard regression analysis with adjustment for serum iron, blood cadmium, serum C-reactive protein, serum calcium, smoking, alcohol intake, race/Hispanic origin, and sex. The adjusted relative risk for CVD mortality was 1.44 (95% confidence interval = 1.05, 1.98) per 10-fold increase in hematocrit-corrected blood lead with little evidence of nonlinearity. Similar results were obtained with hemoglobin-corrected blood lead. Not correcting blood lead for hematocrit/hemoglobin resulted in underestimation of the lead-CVD mortality association while not adjusting for iron status and blood cadmium resulted in overestimation of the lead-CVD mortality association. In a nationally representative sample of U.S. adults, log-transformed blood lead was linearly associated with increased CVD mortality. Correcting blood lead for hematocrit/hemoglobin and adjustments for some biomarkers affected the association.

Serum carbon isotope values change in adults in response to changes in sugar-sweetened beverage intake.

Serum carbon isotope values [13C-to-12C serum carbon isotope ratio (δ(13)C)], which reflect consumption of corn- and cane-based foods, differ between persons consuming high and low amounts of sugar-sweetened beverages (SSBs). In this study, we determined whether serum δ(13)C changes in response to change in SSB intake during an 18-mo behavioral intervention trial. Data were from a subset of 144 participants from the PREMIER trial, a completed behavioral intervention (Maryland, 1998-2004). SSB intake was assessed using 2 24-h dietary recall interviews. Blinded serum samples were assayed for δ(13)C by natural abundance stable isotope mass spectroscopy. Multiple linear regression models with generalized estimating equations and robust variance estimation were used. At baseline, mean SSB intake was 13.8 ± 14.2 fl oz/d, and mean δ(13)C serum value was -19.3 ± 0.6 units per mil (designated ‰). A reduction of 12 oz (355 mL)/d SSB (equivalent to 1 can of soda per day) was associated with 0.17‰ (95% CI: 0.08‰, 0.25‰ P < 0.0001) reduction in serum δ(13)C values over 18 mo (equivalent to a 1% reduction in δ(13)C from baseline). After adjusting for potential confounders, a reduction of 12 oz/d SSB (equivalent to 1 can of soda per day), over an 18-mo period, was associated with 0.12‰ (95% CI: 0.01‰, 0.22‰ P = 0.025) reduction in serum δ(13)C. These findings suggest that serum δ(13)C can be used as a measure of dietary changes in SSB intake.

Physical activity in U.S. youth aged 12-15 years, 2012.

KEY FINDINGS: Data from the combined National Health and Nutrition Examination Survey (NHANES) and the NHANES National Youth Fitness Survey, 2012. In 2012, about one-quarter of U.S. youth aged 12-15 years engaged in moderate-to-vigorous physical activity for at least 60 minutes daily. Basketball was the most common activity reported among active boys, followed by running, football, bike riding, and walking. Running was the most common activity among active girls, followed by walking, basketball, dancing, and bike riding. The percentage of male youth who were physically active for at least 60 minutes daily decreased as weight status increased. The 2008 Physical Activity Guidelines for Americans, which have been adopted by the First Lady's Let's Move! initiative and the American Academy of Pediatrics, recommend that youth participate in daily moderate-to-vigorous physical activity for at least 60 minutes (1-5). This report presents the most recent national data from 2012 on self-reported physical activity among youth aged 12-15 years, by sex and weight status. This report also describes the most common types of physical activities--outside of school-based physical education (PE) or gym classes--in which youth engage.

Trends in sugar-sweetened beverage consumption among youth and adults in the United States: 1999-2010.

BACKGROUND: Reducing sugar-sweetened beverage (SSB) consumption is a recommended strategy to promote optimal health. OBJECTIVE: The objective was to describe trends in SSB consumption among youth and adults in the United States. DESIGN: We analyzed energy intake from SSBs among 22,367 youth aged 2-19 y and 29,133 adults aged ≥20 y who participated in a 24-h dietary recall as part of NHANES, a nationally representative sample of the US population with a cross-sectional design, between 1999 and 2010. SSBs included soda, fruit drinks, sports and energy drinks, sweetened coffee and tea, and other sweetened beverages. Patterns of SSB consumption, including location of consumption and meal occasion associated with consumption, were also examined. RESULTS: In 2009-2010, youth consumed a mean (±SE) of 155 ± 7 kcal/d from SSBs, and adults consumed an age-adjusted mean (±SE) of 151 ± 5 kcal/d from SSBs--a decrease from 1999 to 2000 of 68 kcal/d and 45 kcal/d, respectively (P-trend < 0.001 for each). In 2009-2010, SSBs contributed 8.0% ± 0.4% and 6.9% ± 0.2% of daily energy intake among youth and adults, respectively, which reflected a decrease compared with 1999-2000 (P-trend < 0.001 for both). Decreases in SSB consumption, both in the home and away from home and also with both meals and snacks, occurred over the 12-y study duration (P-trend < 0.01 for each). CONCLUSION: A decrease in SSB consumption among youth and adults in the United States was observed between 1999 and 2010.

Physical activity and screen-time viewing among elementary school-aged children in the United States from 2009 to 2010.

OBJECTIVES To describe the percentage of children who met physical activity and screen-time recommendations and to examine demographic differences. Recommendations for school-aged children include 60 minutes of daily moderate-to-vigorous physical activity and no more than 2 hours per day of screen-time viewing. DESIGN Cross-sectional study. SETTING Data from the 2009-2010 National Health and Nutrition Examination Survey, a representative sample of the US population. PARTICIPANTS Analysis included 1218 children 6 to 11 years of age. MAIN EXPOSURES Age, race/ethnicity, sex, income, family structure, and obesity status. MAIN OUTCOME MEASURES Proxy-reported adherence to physical activity and screen-time recommendations, separately and concurrently. RESULTS Based on proxy reports, overall, 70% of children met physical activity recommendations, and 54% met screen-time viewing recommendations. Although Hispanics were less likely to meet physical activity recommendations (adjusted odds ratio [aOR], 0.60 [95% CI, 0.38-0.95]), they were more likely to meet screen-time recommendations compared with non-Hispanic whites (aOR, 1.69 [95% CI, 1.18-2.43]). Only 38% met both recommendations concurrently. Age (9-11 years vs 6-8 years: aOR, 0.57 [95% CI, 0.38-0.85]) and obesity (aOR, 0.53 [95% CI, 0.38-0.73]) were inversely associated with concurrent adherence to both recommendations. CONCLUSIONS Fewer than 4 in 10 children met both physical activity and screen-time recommendations concurrently. The prevalence of sedentary behavior was higher in older children. Low levels of screen-time viewing may not necessarily predict higher levels of physical activity.

Prevalence of obesity among older adults in the United States, 2007-2010.

By 2050, the number of U.S. older adults, defined as persons aged 65 and over, is expected to more than double, rising from 40.2 million to 88.5 million (1). Both aging and obesity contribute to increased health care service use (2,3). Consequently, an increase in the proportion of older adults who are obese may compound health care spending. Given the demographic changes forecasted and the potential health care costs of obesity, it is important to track the prevalence of obesity among older adults (2,3). This report presents the most recent national estimates of obesity in older adults, by sex, age, race and ethnicity, and educational attainment, and examines changes in the prevalence of obesity between 1999 and 2010.

Consumption of diet drinks in the United States, 2009‒2010.

Sugar drinks are a major source of added sugars in the diets of Americans (1). Several recent studies have described factors associated with sugar-drink consumption (2,3); however, the consumption of diet drinks among the U.S. population has not been as well-characterized. This report describes the consumption of diet beverages among the U.S. population during 2009‒2010 by sex, age, race and ethnicity, and income, and details trends in diet drink consumption from 1999‒2000 through 2009‒2010.

Abdominal obesity, body mass index, and hypertension in US adults: NHANES 2007-2010.

BACKGROUND: Both abdominal obesity, defined as waist circumference (WC) ≥ 102 cm for men and WC ≥ 88 cm for women and increased body mass index (BMI; kg/m²) are known to be associated with hypertension. The aim of this study was to examine the independent and the combined relationship between abdominal obesity and increased BMI and hypertension by age, race, and gender in a national sample. METHODS: This report is based on national level cross-sectional data for adults aged 18 years and older (11,145 participants) from the US National Health and Nutrition Examination Survey (NHANES) 2007-2010. RESULTS: Abdominal obesity, after adjusting for BMI categories and other covariables, was independently associated with hypertension. That is, survey participants classified as abdominally obese had almost 50% increased odds of being hypertensive (odds ratio (OR) 1.51, 95% confidence interval (CI) 1.27-1.81) after controlling for BMI. After adjusting for covariables, the groups of individuals classified as abdominally obese and normal BMI; as abdominally obese and overweight; and abdominally obese and obese each had a progressive increase in the odds of hypertension when compared with individuals who had a normal BMI and no abdominal obesity (OR 1.81, 95% CI 1.28-2.57, OR 1.87, 95% CI 1.55-2.25, and OR 3.23, 95% CI 2.63-3.96, respectively). CONCLUSIONS: Abdominal obesity is independently associated with hypertension after adjusting for BMI. After adjusting for covariables and parameterizing BMI categories and abdominal obesity the new variable showed a progressive increase in the odds of hypertension. Both BMI and WC should be included in models assessing hypertension risks.

Dynamic chromatin organization during foregut development mediated by the organ selector gene PHA-4/FoxA.

Central regulators of cell fate, or selector genes, establish the identity of cells by direct regulation of large cohorts of genes. In Caenorhabditis elegans, foregut (or pharynx) identity relies on the FoxA transcription factor PHA-4, which activates different sets of target genes at various times and in diverse cellular environments. An outstanding question is how PHA-4 distinguishes between target genes for appropriate transcriptional control. We have used the Nuclear Spot Assay and GFP reporters to examine PHA-4 interactions with target promoters in living embryos and with single cell resolution. While PHA-4 was found throughout the digestive tract, binding and activation of pharyngeally expressed promoters was restricted to a subset of pharyngeal cells and excluded from the intestine. An RNAi screen of candidate nuclear factors identified emerin (emr-1) as a negative regulator of PHA-4 binding within the pharynx, but emr-1 did not modulate PHA-4 binding in the intestine. Upon promoter association, PHA-4 induced large-scale chromatin de-compaction, which, we hypothesize, may facilitate promoter access and productive transcription. Our results reveal two tiers of PHA-4 regulation. PHA-4 binding is prohibited in intestinal cells, preventing target gene expression in that organ. PHA-4 binding within the pharynx is limited by the nuclear lamina component EMR-1/emerin. The data suggest that association of PHA-4 with its targets is a regulated step that contributes to promoter selectivity during organ formation. We speculate that global re-organization of chromatin architecture upon PHA-4 binding promotes competence of pharyngeal gene transcription and, by extension, foregut development.