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.

A roundtable to discuss the measurement of folate status biomarkers in NHANES took place in July 2010. NHANES has measured serum folate since 1974 and red blood cell (RBC) folate since 1978 with the use of several different measurement procedures. Data on serum 5-methyltetrahydrofolate (5MTHF) and folic acid (FA) concentrations in persons aged ≥60 y are available in NHANES 1999-2002. The roundtable reviewed data that showed that folate concentrations from the Bio-Rad Quantaphase II procedure (Bio-Rad Laboratories, Hercules, CA; used in NHANES 1991-1994 and NHANES 1999-2006) were, on average, 29% lower for serum and 45% lower for RBC than were those from the microbiological assay (MA), which was used in NHANES 2007-2010. Roundtable experts agreed that these differences required a data adjustment for time-trend analyses. The roundtable reviewed the possible use of an isotope-dilution liquid chromatography-tandem mass spectrometry (LC-MS/MS) measurement procedure for future NHANES and agreed that the close agreement between the MA and LC-MS/MS results for serum folate supported conversion to the LC-MS/MS procedure. However, for RBC folate, the MA gave 25% higher concentrations than did the LC-MS/MS procedure. The roundtable agreed that the use of the LC-MS/MS procedure to measure RBC folate is premature at this time. The roundtable reviewed the reference materials available or under development at the National Institute of Standards and Technology and recognized the challenges related to, and the scientific need for, these materials. They noted the need for a commutability study for the available reference materials for serum 5MTHF and FA.

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. Published in 2010 by John Wiley & Sons, Ltd.

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.

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.

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.

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 ≥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.Published online January 13, 2010 (doi:10.1001/jama.2009.2014).

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 (≥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 ≥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.Published online January 13, 2010 (doi:10.1001/jama.2009.2012).

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 BMI-for-age by using simple functions of the CDC growth charts. DESIGN: Empirical data for the 99th and the 1st percentiles of body mass index (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.