National Health and Nutrition Examination Survey: sample design, 2007-2010.

BACKGROUND: Data collection for the National Health and Nutrition Examination Survey (NHANES) comprises three levels: a household screener, an interview, and a physical examination. The primary objective of the screener is to determine whether any household members are eligible for the interview an dexamination. Eligibility is determined by preset selection probabilities for the desired demographic subdomains. After an eligible sample person is selected, the interview collects person-level demographic, health, and nutrition information, as well as information about the household. The examination includes physical measurements, tests such as hearing and dental examinations, and the collection of blood and urine specimens for laboratory testing. OBJECTIVES: This report provides some background on the NHANES program, beginning with the first survey cycle in the 1970s and highlighting significant changes since its inception. The report then describes the broad design specifications for the 2007-2010 survey cycle, including survey objectives, domain and precision specifications, and operational requirements unique to NHANES. In addition, the report describes the details of the survey design, including the calculation of sampling rates and sample selection methods. Documentation of survey content, data collection procedures, estimation methods, and methods to assess nonsampling errors are reported elsewhere.

National health and nutrition examination survey: analytic guidelines, 1999-2010.

Background-Analytic guide lines were first created in 1996 to assist data users in analyzing data from the Third National Health and Nutrition Examination Survey (NHANES III),conducted from 1988 to 1994 by the Centers for Disease Control and Prevention's National Center for Health Statistics. NHANES became a continuous annual survey in 1999, with data released to the public in 2-year intervals. In 2002, 2004, and 2006, guidelines were created and posted on the NHANES website to assist analysts in understanding the key issues related to analyzing data from 1999 onward. This report builds on these previous guidelines and provides the first comprehensive summary of analytic guidelines for the 1999-2010 NHANES data. Objectives-This report provides general guidelines for researchers in analyzing 1999-2010 NHANES publicly released data. Information is presented on key issues related to NHANES data, including sample design, demographic variables, and combining survey cycles. Guidance is also provided on data analysis, including the use of appropriate survey weights, calculating variance estimations, determining the reliability of estimates, age adjustment, and computing population counts.

National Health and Nutrition Examination Survey: estimation procedures, 2007-2010.

BACKGROUND: Data collection for the National Health and Nutrition Examination Survey (NHANES), comprises three levels: an initial household screening interview (or ''screener''), an in-home personal interview, and a physical examination. The primary objective of the screener is to determine whether any household members are eligible for the interview and examination. Eligibility is determined by preset selection probabilities for the desired demographic subdomains. After an eligible sample person is selected, the in-home interview collects person-level demographic, health, and nutrition information, as well as information about the household. The examination includes physical measurements such as blood pressure, a dental examination, and the collection of blood and urine specimens for laboratory testing. OBJECTIVES: This report provides background for the NHANES program and summarizes the sample design specifications for the 2007-2010 survey cycle. Estimation procedures are then presented, including the methods used to calculate survey weights for the full sample and for examination subsamples, as well as guidelines for combining 2-year weights for the analysis of multiyear data. Finally, the appropriate variance estimation methods are described. The sample selection methods, survey content, data collection procedures, and methods for assessing nonsampling errors are documented elsewhere.

The National Health and Nutrition Examination Survey: Sample Design, 1999-2006.

BACKGROUND: Data collection for the National Health and Nutrition Examination Survey (NHANES) comprises three levels: a household screener, an interview, and a physical examination. The primary objective of the screener is to determine whether any household members are eligible for the interview and examination. Eligibility is determined by the preset selection probabilities for the desired demographic subdomains. After selection as an eligible sample person, the interview collects person-level demographic, health, and nutrition information as well as information about the household. The examination includes physical measurements, tests such as eye and dental examinations, and the collection of blood and urine specimens for laboratory testing. OBJECTIVES: This report will first describe the broad design specifications for the 1999-2006 survey including survey objectives, domain and precision specifications, operational requirements, sample design, and estimations procedures. Details of the sample design are divided into two sections. The first section (NHANES 1999-2001 Sample Design) broadly describes the sample design and various design changes during the first three years of the continuous NHANES (1999-2001). The second section (NHANES 2002-2006 Sample Design) describes the final sample design developed and applied for 2002-2006. Weighting and variance estimation procedures are presented in the same manner; however, to correspond to the public data release cycles, the weighting and variance sections are separated into those used for 1999-2002, and those used for 2003-2006. Much of this report is based on survey operations documents and sample design reports prepared by Westat. Documentation of the survey content, procedures, and methods to assess nonsampling errors are reported elsewhere.

U.S. decennial life tables for 1999-2001: state life tables.

OBJECTIVE: This report, following publication of the national life tables (1,2) for 1999-2001, presents state-specific life tables for the 50 states and District of Columbia by race (white and black) and sex. These tables are the most recent in a series of decennial life tables for the United States. METHODS: Data used to prepare these state-specific life tables include population counts by age on the census date of April 1, 2000; deaths occurring in the 3-year period of 1999-2001; and counts of U.S. resident births during 1997-2001. Methods for calculating the life tables were modified from the previous decennial life tables to automate the smoothing of age-specific mortality data and to allow for the estimation of life tables for smaller population subgroups, which often had insufficient data available to estimate reliable life tables under the previous method. The current method allows for the estimation of life tables for the black population in six states, which were never previously published due to small numbers of deaths. Standard errors for estimating life expectancy and probability of dying are also presented in this report. RESULTS: Among the 50 states, Hawaii had the highest life expectancy at birth during the 1999-2001 period at 80.23 years, and Mississippi had the lowest life expectancy at 73.88 years. Life expectancy for the District of Columbia was even lower at 73.09 years. State-specific life expectancy at birth improved from the previous decennial period (1989-1991) for all states and the District of Columbia. Life expectancy at age 65 ranged from 20.42 years in Hawaii to 16.61 years in Kentucky. Life expectancy at age 65 also improved for all states except Kentucky.

Health of adults in Los Angeles County: findings from the National Health and Nutrition Examination Survey, 1999-2004.

OBJECTIVE: Los Angeles County has the largest population of any county in the nation. Population-based estimates of health conditions for Los Angeles County are based primarily on telephone surveys, which are known to underestimate conditions of public health importance. This report presents the prevalence of selected health conditions for civilian noninstitutionalized adults aged 20 and over living in Los Angeles County households and group quarters, based on survey data using direct physical measurements. METHODS: Combined data from the 1999-2000, 2001-2002, and 2003-2004 National Health and Nutrition Examination Surveys (NHANES), conducted by the Centers for Disease Control and Prevention's National Center for Health Statistics, were used for this report. Sample weights were recalculated for participants examined in Los Angeles County using population totals provided by the Los Angeles County Department of Public Health, excluding the institutionalized population. RESULTS: Compared with the nation as a whole, adults in Los Angeles County had similar rates of health conditions even after age and age-race adjustment, with a few exceptions. A significantly smaller proportion of Los Angeles County adults were obese (age-adjusted rate, 23.8%) compared with the United States (31.0%); this difference held after age-race adjustment. The age-adjusted rate of diagnosed diabetes for men was higher in Los Angeles County (9.1%) than in the nation (7.3%); however, this difference did not hold after age-race adjustment. The rates of total diabetes adjusted for age and age-race were similar for men in Los Angeles County and the United States. CONCLUSIONS: The rates of selected health conditions in this report were similar for adults in Los Angeles County compared with adults in the United States, with the exception of obesity. The rates of obesity adjusted for age and age-race were lower among Los Angeles County adults compared with national rates. Health estimates based on direct physical measurements can be useful for local public health programs and prevention efforts.

Multiple imputation of missing dual-energy X-ray absorptiometry data in the National Health and Nutrition Examination Survey.

In 1999, dual-energy x-ray absorptiometry (DXA) scans were added to the National Health and Nutrition Examination Survey (NHANES) to provide information on soft tissue composition and bone mineral content. However, in 1999-2004, DXA data were missing in whole or in part for about 21 per cent of the NHANES participants eligible for the DXA examination; and the missingness is associated with important characteristics such as body mass index and age. To handle this missing-data problem, multiple imputation of the missing DXA data was performed. Several features made the project interesting and challenging statistically, including the relationship between missingness on the DXA measures and the values of other variables; the highly multivariate nature of the variables being imputed; the need to transform the DXA variables during the imputation process; the desire to use a large number of non-DXA predictors, many of which had small amounts of missing data themselves, in the imputation models; the use of lower bounds in the imputation procedure; and relationships between the DXA variables and other variables, which helped both in creating and evaluating the imputations. This paper describes the imputation models, methods, and evaluations for this publicly available data resource and demonstrates properties of the imputations via examples of analyses of the data. The analyses suggest that imputation helps to correct biases that occur in estimates based on the data without imputation, and that it helps to increase the precision of estimates as well. Moreover, multiple imputation usually yields larger estimated standard errors than those obtained with single imputation.

Statistical and practical issues in the design of a national probability sample of births for the Vanguard Study of the National Children's Study.

The National Children's Study is a national household probability sample designed to identify 100,000 children at birth and follow the sampled children for 21 years. Data from the study will support examining numerous hypotheses concerning genetic and environmental effects on the health and development of children. The goals of the study present substantial challenges. For example, the need for preconception, prenatal, and postnatal data requires identifying women in the early stages of pregnancy, the collection of many types of data, and the retention of the children over time. In this paper, we give an overview of the sample design used in a pilot study called the Vanguard Study, and highlight the approaches used to address these challenges. We will also describe the rationale for the sampling choices made at each stage, the unique organizational structure of the NCS and issues we expect to face during implementation.

The 2000 Centers for Disease Control and Prevention growth charts: several insights after 8 years.

This paper explores three issues related to the 2000 Centers for Disease Control and Prevention growth charts. First, it clarifies the methods that were used to create the charts as it has become apparent that the smoothing techniques have been somewhat misunderstood. The techniques included smoothing-selected percentiles between and including the 3rd and 97th percentiles and then approximating these smoothed curves using a procedure to provide the transformation parameters, lambda, mu, and sigma. Only the selected percentiles were used in this process due to small sample sizes beyond these percentiles. Second, given the concern that the infant charts were created with relatively few data points in the first few months of life, it compares the original observed percentiles with percentiles that include newly available US national data for the first few months of life. Third, it discusses the issues that arise if a 99th percentile is extrapolated based on the lambda, mu, and sigma parameters. The 99th percentile of the body mass index-for-age chart has been recommended to identify extremely obese children, yet the 97th percentile is the highest available percentile on the Centers for Disease Control and Prevention growth charts.

Cardiorespiratory fitness levels among US adults 20-49 years of age: findings from the 1999-2004 National Health and Nutrition Examination Survey.

Data from the 1999-2004 National Health and Nutrition Examination Survey were used to describe the distribution of cardiorespiratory fitness and its association with obesity and leisure-time physical activity (LTPA) for adults 20-49 years of age without physical limitations or indications of cardiovascular disease. A sample of 7,437 adults aged 20-49 years were examined at a mobile examination center. Of 4,860 eligible for a submaximal treadmill test, 3,250 completed the test and were included in the analysis. The mean maximal oxygen uptake ( max) was estimated as 44.5, 42.8, and 42.2 mL/kg/minute for men 20-29, 30-39, and 40-49 years of age, respectively. For women, it was 36.5, 35.4, and 34.4 mL/kg/minute for the corresponding age groups. Non-Hispanic black women had lower fitness levels than did non-Hispanic white and Mexican-American women. Regardless of gender or race/ethnicity, people who were obese had a significantly lower estimated maximal oxygen uptake than did nonobese adults. Furthermore, a positive association between fitness level and LTPA participation was observed for both men and women. These results can be used to track future population assessments and to evaluate interventions. The differences in fitness status among population subgroups and by obesity status or LTPA can also be used to develop health policies and targeted educational campaigns.

Prevalence of high body mass index in US children and adolescents, 2007-2008.

CONTEXT: The prevalence of high body mass index (BMI) among children and adolescents in the United States appeared to plateau between 1999 and 2006. OBJECTIVES: To provide the most recent estimates of high BMI among children and adolescents and high weight for recumbent length among infants and toddlers and to analyze trends in prevalence between 1999 and 2008. DESIGN, SETTING, AND PARTICIPANTS: The National Health and Nutrition Examination Survey 2007-2008, a representative sample of the US population with measured heights and weights on 3281 children and adolescents (2 through 19 years of age) and 719 infants and toddlers (birth to 2 years of age). MAIN OUTCOME MEASURES: Prevalence of high weight for recumbent length (> or = 95th percentile of the Centers for Disease Control and Prevention growth charts) among infants and toddlers. Prevalence of high BMI among children and adolescents defined at 3 levels: BMI for age at or above the 97th percentile, at or above the 95th percentile, and at or above the 85th percentile of the BMI-for-age growth charts. Analyses of trends by age, sex, and race/ethnicity from 1999-2000 to 2007-2008. RESULTS: In 2007-2008, 9.5% of infants and toddlers (95% confidence interval [CI], 7.3%-11.7%) were at or above the 95th percentile of the weight-for-recumbent-length growth charts. Among children and adolescents aged 2 through 19 years, 11.9% (95% CI, 9.8%-13.9%) were at or above the 97th percentile of the BMI-for-age growth charts; 16.9% (95% CI, 14.1%-19.6%) were at or above the 95th percentile; and 31.7% (95% CI, 29.2%-34.1%) were at or above the 85th percentile of BMI for age. Prevalence estimates differed by age and by race/ethnic group. Trend analyses indicate no significant trend between 1999-2000 and 2007-2008 except at the highest BMI cut point (BMI for age > or = 97th percentile) among all 6- through 19-year-old boys (odds ratio [OR], 1.52; 95% CI, 1.17-2.01) and among non-Hispanic white boys of the same age (OR, 1.87; 95% CI, 1.22-2.94). CONCLUSION: No statistically significant linear trends in high weight for recumbent length or high BMI were found over the time periods 1999-2000, 2001-2002, 2003-2004, 2005-2006, and 2007-2008 among girls and boys except among the very heaviest 6- through 19-year-old boys.

Prevalence and trends in obesity among US adults, 1999-2008.

CONTEXT: The prevalence of obesity increased in the United States between 1976-1980 and 1988-1994 and again between 1988-1994 and 1999-2000. OBJECTIVE: To examine trends in obesity from 1999 through 2008 and the current prevalence of obesity and overweight for 2007-2008. DESIGN, SETTING, AND PARTICIPANTS: Analysis of height and weight measurements from 5555 adult men and women aged 20 years or older obtained in 2007-2008 as part of the National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of the US population. Data from the NHANES obtained in 2007-2008 were compared with results obtained from 1999 through 2006. MAIN OUTCOME MEASURE: Estimates of the prevalence of overweight and obesity in adults. Overweight was defined as a body mass index (BMI) of 25.0 to 29.9. Obesity was defined as a BMI of 30.0 or higher. RESULTS: In 2007-2008, the age-adjusted prevalence of obesity was 33.8% (95% confidence interval [CI], 31.6%-36.0%) overall, 32.2% (95% CI, 29.5%-35.0%) among men, and 35.5% (95% CI, 33.2%-37.7%) among women. The corresponding prevalence estimates for overweight and obesity combined (BMI > or = 25) were 68.0% (95% CI, 66.3%-69.8%), 72.3% (95% CI, 70.4%-74.1%), and 64.1% (95% CI, 61.3%-66.9%). Obesity prevalence varied by age group and by racial and ethnic group for both men and women. Over the 10-year period, obesity showed no significant trend among women (adjusted odds ratio [AOR] for 2007-2008 vs 1999-2000, 1.12 [95% CI, 0.89-1.32]). For men, there was a significant linear trend (AOR for 2007-2008 vs 1999-2000, 1.32 [95% CI, 1.12-1.58]); however, the 3 most recent data points did not differ significantly from each other. CONCLUSIONS: In 2007-2008, the prevalence of obesity was 32.2% among adult men and 35.5% among adult women. The increases in the prevalence of obesity previously observed do not appear to be continuing at the same rate over the past 10 years, particularly for women and possibly for men.

Characterizing extreme values of body mass index-for-age by using the 2000 Centers for Disease Control and Prevention growth charts.

BACKGROUND: The 2000 Centers for Disease Control and Prevention (CDC) growth charts included lambda-mu-sigma (LMS) parameters intended to calculate smoothed percentiles from only the 3rd to the 97th percentile. OBJECTIVE: The objective was to evaluate different approaches to describing more extreme values of body mass index (BMI)-for-age by using simple functions of the CDC growth charts. DESIGN: Empirical data for the 99th and the 1st percentiles of BMI-for-age were calculated from the data set used to construct the growth charts and were compared with estimates extrapolated from the CDC-supplied LMS parameters and to various functions of other smoothed percentiles. A set of reestimated LMS parameters that incorporated a smoothed 99th percentile were also evaluated. RESULTS: Extreme percentiles extrapolated from the CDC-supplied LMS parameters did not match well to the empirical data for the 99th percentile. A better fit to the empirical data was obtained by using 120% of the smoothed 95th percentile. The empirical first percentile was reasonably well approximated by extrapolations from the LMS values. The reestimated LMS parameters had several drawbacks and no clear advantages. CONCLUSIONS: Several approximations can be used to describe extreme high values of BMI-for-age with the use of the CDC growth charts. Extrapolation from the CDC-supplied LMS parameters does not provide a good fit to the empirical 99th percentile values. Simple approximations to high values as percentages of the existing smoothed percentiles have some practical advantages over imputation of very high percentiles. The expression of high BMI values as a percentage of the 95th percentile can provide a flexible approach to describing and tracking heavier children.

U.S. decennial life tables for 1999-2001, United States life tables.

OBJECTIVES: This report presents period life tables for the United States based on age-specific death rates for the period 1999-2001. These tables are the most recent in a 100-year series of decennial life tables for the United States. METHODS: This report presents complete life tables by age, race (white and black), and sex. Also presented are standard errors of the probability of dying and life expectancy. The data used to prepare these life tables are population estimates based on the 2000 decennial census, deaths occurring in the United States to U.S. residents in the 3 years 1999-2001, counts of U.S. resident births in the years 1997-2001, and population and death counts from the Medicare program for years 1999-2001. RESULTS: In 1999-2001, life expectancy at birth was 76.83 years for the total U.S. population, representing an increase of 27.59 years from a life expectancy of 49.24 years in 1900. Between 1900 and 2000, life expectancy increased by 40.08 years for black females (from 35.04 to 75.12), by 35.54 years for black males (from 32.54 to 68.08), by 28.89 years for white females (from 51.08 to 79.97), and by 26.51 years for white males (from 48.23 to 74.74).

U.S. decennial life tables for 1999-2001: methodology of the United States Life Tables.

OBJECTIVES: This report describes the methodology used in the preparation of the 1999-2001 decennial life tables for the United States. METHODS: Data used to prepare these life tables include population data by age on the census date April 1, 2000; deaths occurring in the 3-year period 1999-2001 classified by age at death; births for each of the years 1997-2001; and Medicare data for ages 66-100 years from the years 1999-2001. Methods that were kept the same as those of previous decennial tables include data sources used in constructing tables, the preliminary adjustment for misreported ages, the smoothing techniques for vital statistics and census data, and the calculations of death rates in different age groups. Two significant changes were made to the methodology used to estimate mortality for the populations aged 66 years and over. First, Medicare data were used to supplement vital statistics (number of deaths) and census data (population estimates) starting at age 66 years instead of age 85 years as was done in the estimation of previous U.S. decennial life tables. Second, smoothing and extrapolation of death rates for ages 66-109 was performed using a mathematical model given by Heligman and Pollard, instead of a Whittaker-Henderson Type B formula or modified Gompertz method.

Smoke-free laws and secondhand smoke exposure in US non-smoking adults, 1999-2002.

OBJECTIVES: To investigate the relationship between smoke-free law coverage and secondhand smoke (SHS) exposure in the United States non-smoking adult population. DESIGN: We used data from the 1999-2002 National Health and Nutrition Examination Survey, a cross-sectional survey designed to monitor the health and nutritional status of the US population. Serum cotinine levels were available for 5866 non-smoking adults from 57 survey locations. Each location was categorised into one of three groups indicating extensive, limited, and no coverage by a smoke-free law. MAIN OUTCOME MEASURES: The proportion of adults with SHS exposure, defined as having serum cotinine levels > or = 0.05 ng/ml. RESULTS: Among non-smoking adults living in counties with extensive smoke-free law coverage, 12.5% were exposed to SHS, compared with 35.1% with limited coverage, and 45.9% with no law. Adjusting for confounders, men and women residing in counties with extensive coverage had 0.10 (95% confidence interval (CI) 0.06 to 0.16) and 0.19 (95% CI 0.11 to 0.34) times the odds of SHS exposure compared to those residing in counties without a smoke-free law. CONCLUSIONS: These results support the scientific evidence suggesting that smoke-free laws are an effective strategy for reducing SHS exposure.

Prevalence of overweight and obesity in the United States, 1999-2004.

CONTEXT: The prevalence of overweight in children and adolescents and obesity in adults in the United States has increased over several decades. OBJECTIVE: To provide current estimates of the prevalence and trends of overweight in children and adolescents and obesity in adults. DESIGN, SETTING, AND PARTICIPANTS: Analysis of height and weight measurements from 3958 children and adolescents aged 2 to 19 years and 4431 adults aged 20 years or older obtained in 2003-2004 as part of the National Health and Nutrition Examination Survey (NHANES), a nationally representative sample of the US population. Data from the NHANES obtained in 1999-2000 and in 2001-2002 were compared with data from 2003-2004. MAIN OUTCOME MEASURES: Estimates of the prevalence of overweight in children and adolescents and obesity in adults. Overweight among children and adolescents was defined as at or above the 95th percentile of the sex-specific body mass index (BMI) for age growth charts. Obesity among adults was defined as a BMI of 30 or higher; extreme obesity was defined as a BMI of 40 or higher. RESULTS: In 2003-2004, 17.1% of US children and adolescents were overweight and 32.2% of adults were obese. Tests for trend were significant for male and female children and adolescents, indicating an increase in the prevalence of overweight in female children and adolescents from 13.8% in 1999-2000 to 16.0% in 2003-2004 and an increase in the prevalence of overweight in male children and adolescents from 14.0% to 18.2%. Among men, the prevalence of obesity increased significantly between 1999-2000 (27.5%) and 2003-2004 (31.1%). Among women, no significant increase in obesity was observed between 1999-2000 (33.4%) and 2003-2004 (33.2%). The prevalence of extreme obesity (body mass index > or =40) in 2003-2004 was 2.8% in men and 6.9% in women. In 2003-2004, significant differences in obesity prevalence remained by race/ethnicity and by age. Approximately 30% of non-Hispanic white adults were obese as were 45.0% of non-Hispanic black adults and 36.8% of Mexican Americans. Among adults aged 20 to 39 years, 28.5% were obese while 36.8% of adults aged 40 to 59 years and 31.0% of those aged 60 years or older were obese in 2003-2004. CONCLUSIONS: The prevalence of overweight among children and adolescents and obesity among men increased significantly during the 6-year period from 1999 to 2004; among women, no overall increases in the prevalence of obesity were observed. These estimates were based on a 6-year period and suggest that the increases in body weight are continuing in men and in children and adolescents while they may be leveling off in women.

Limitations of follicle-stimulating hormone in assessing menopause status: findings from the National Health and Nutrition Examination Survey (NHANES 1999-2000)*.

OBJECTIVE: We used data from the National Health and Nutrition Examination Survey (NHANES 1999-2000) to: establish new population-based estimates for follicle-stimulating hormone (FSH) and luteinizing hormone (LH); identify factors associated with FSH; and assess its efficacy in distinguishing among women in the reproductive, menopause transition, and postmenopausal stages. DESIGN: Nationally representative sample of 576 women aged 35 to 60 years examined during NHANES 1999-2000. RESULTS: Levels of FSH and LH increased significantly with reproductive stage. (Geometric mean FSH levels for successive stages: reproductive, 7.0 mIU/mL, SE 0.4; menopause transition, 21.9 mIU/mL, SE 3.7; and postmenopause, 45.7 mIU/mL, SE 4.3). There was considerable overlap, however, among distributions of FSH by stage. Only age and reproductive stage were significantly associated with FSH in multivariable analysis. FSH cutoff points between the reproductive and menopause transition stages [FSH = 13 mIU/mL, sensitivity 67.4% (95% CI 50.0-81.1), specificity 88.1% (95% CI 81.1-92.8)] and between the menopause transition and postmenopause stages [FSH = 45 mIU/mL, sensitivity 73.6% (95% CI 60.1-83.7), specificity 70.6% (95% CI 52.4-84.0)] were neither sensitive nor very specific. CONCLUSIONS: Age and reproductive stage are the most important determinants of FSH levels in US women; however, FSH by itself has limited utility in distinguishing among women in different reproductive stages.

Racial and ethnic differences in the seroprevalence of 6 infectious diseases in the United States: data from NHANES III, 1988-1994.

OBJECTIVES: We examined racial/ethnic differences in the seroprevalence of selected infectious agents in analyses stratified according to risk categories to identify patterns and to determine whether demographic, socioeconomic, and behavioral characteristics explain these differences. METHODS: We analyzed data from the third National Health and Nutrition Examination Survey, comparing differences among groups in regard to the prevalence of infection with hepatitis A, B, and C viruses, Toxoplasma gondii, Helicobacter pylori, and herpes simplex virus type 2. RESULTS: Racial/ethnic differences were greater among those in the low-risk category. In the case of most infectious agents, odds associated with race/ethnicity were almost 2 times greater in that category than in the high-risk category. CONCLUSIONS: Stratification and adjustment for socioeconomic factors reduced or eliminated racial/ethnic differences in the prevalence of infection in the high-risk but not the low-risk group, wherein race/ethnicity remained significant and might have been a surrogate for unmeasured risk factors.

Prevalence of overweight and obesity among US children, adolescents, and adults, 1999-2002.

CONTEXT: The prevalence of overweight and obesity has increased markedly in the last 2 decades in the United States. OBJECTIVE: To update the US prevalence estimates of overweight in children and obesity in adults, using the most recent national data of height and weight measurements. DESIGN, SETTING, AND PARTICIPANTS: As part of the National Health and Nutrition Examination Survey (NHANES), a complex multistage probability sample of the US noninstitutionalized civilian population, both height and weight measurements were obtained from 4115 adults and 4018 children in 1999-2000 and from 4390 adults and 4258 children in 2001-2002. MAIN OUTCOME MEASURE: Prevalence of overweight (body mass index [BMI] > or =95th percentile of the sex-specific BMI-for-age growth chart) among children and prevalence of overweight (BMI, 25.0-29.9), obesity (BMI > or =30.0), and extreme obesity (BMI > or =40.0) among adults by sex, age, and racial/ethnic group. RESULTS: Between 1999-2000 and 2001-2002, there were no significant changes among adults in the prevalence of overweight or obesity (64.5% vs 65.7%), obesity (30.5% vs 30.6%), or extreme obesity (4.7% vs 5.1%), or among children aged 6 through 19 years in the prevalence of at risk for overweight or overweight (29.9% vs 31.5%) or overweight (15.0% vs 16.5%). Overall, among adults aged at least 20 years in 1999-2002, 65.1% were overweight or obese, 30.4% were obese, and 4.9% were extremely obese. Among children aged 6 through 19 years in 1999-2002, 31.0% were at risk for overweight or overweight and 16.0% were overweight. The NHANES results indicate continuing disparities by sex and between racial/ethnic groups in the prevalence of overweight and obesity. CONCLUSIONS: There is no indication that the prevalence of obesity among adults and overweight among children is decreasing. The high levels of overweight among children and obesity among adults remain a major public health concern.