DESIGN, SETTING, AND PARTICIPANTS Analysis of data obtained from the National Health and Nutrition Examination Survey (NHANES), a cross-sectional, nationally representative health examination survey of the US civilian noninstitutionalized population that includes measured weight and height. EXPOSURES Survey period. MAIN OUTCOMES AND MEASURES Prevalence of obesity (body mass index Ն30) and class 3 obesity (body mass index Ն40). RESULTS This report is based on data from 2638 adult men (mean age, 46.8 years) and 2817 women (mean age, 48.4 years) from the most recent 2 years (2013-2014) of NHANES and data from 21 013 participants in previous NHANES surveys from 2005 through 2012. For the years 2013-2014, the overall age-adjusted prevalence of obesity was 37.7% (95% CI, 35.8%-39.7%); among men, it was 35.0% (95% CI, 32.8%-37.3%); and among women, it was 40.4% (95% CI, 37.6%-43.3%). The corresponding prevalence of class 3 obesity overall was 7.7% (95% CI, 6.2%-9.3%); among men, it was 5.5% (95% CI, 4.0%-7.2%); and among women, it was 9.9% (95% CI, 7.5%-12.3%). Analyses of changes over the decade from 2005 through 2014, adjusted for age, race/Hispanic origin, smoking status, and education, showed significant increasing linear trends among women for overall obesity (P = .004) and for class 3 obesity (P = .01) but not among men (P = .30 for overall obesity; P = .14 for class 3 obesity). CONCLUSIONS AND RELEVANCE In this nationally representative survey of adults in the United States, the age-adjusted prevalence of obesity in 2013-2014 was 35.0% among men and 40.4% among women. The corresponding values for class 3 obesity were 5.5% for men and 9.9% for women. For women, the prevalence of overall obesity and of class 3 obesity showed significant linear trends for increase between 2005 and 2014; there were no significant trends for men. Other studies are needed to determine the reasons for these trends.

IMPORTANCE Previous analyses of obesity trends among children and adolescents showed an increase between 1988–1994 and 1999–2000, but no change between 2003–2004 and 2011–2012, except for a significant decline among children aged 2 to 5 years. OBJECTIVES To provide estimates of obesity and extreme obesity prevalence for children and adolescents for 2011–2014 and investigate trends by age between 1988–1994 and 2013–2014. DESIGN, SETTING, AND PARTICIPANTS Children and adolescents aged 2 to 19 years with measured weight and height in the 1988–1994 through 2013–2014 National Health and Nutrition Examination Surveys. EXPOSURES Survey period. MAIN OUTCOMES AND MEASURES Obesity was defined as a body mass index (BMI) at or above the sex-specific 95th percentile on the US Centers for Disease Control and Prevention (CDC) BMI-for-age growth charts. Extreme obesity was defined as a BMI at or above 120% of the sex-specific 95th percentile on the CDC BMI-for-age growth charts. Detailed estimates are presented for 2011–2014. The analyses of linear and quadratic trends in prevalence were conducted using 9 survey periods. Trend analyses between 2005–2006 and 2013–2014 also were conducted. RESULTS Measurements from 40 780 children and adolescents (mean age, 11.0 years; 48.8% female) between 1988–1994 and 2013–2014 were analyzed. Among children and adolescents aged 2 to 19 years, the prevalence of obesity in 2011–2014 was 17.0% (95% CI, 15.5%−18.6%) and extreme obesity was 5.8% (95% CI, 4.9%−6.8%). Among children aged 2 to 5 years, obesity increased from 7.2% (95% CI, 5.8%−8.8%) in 1988–1994 to 13.9% (95% CI,10.7%−17.7%) (P < .001) in 2003–2004 and then decreased to 9.4% (95% CI, 6.8%−12.6%)(P = .03) in 2013–2014. Among children aged 6 to 11 years, obesity increased from 11.3% (95% CI, 9.4%−13.4%) in 1988–1994 to 19.6% (95% CI, 17.1%−22.4%) (P < .001) in 2007–2008, and then did not change (2013–2014: 17.4% [95% CI, 13.8%−21.4%]; P = .44). Obesity increased among adolescents aged 12 to 19 years between 1988–1994 (10.5% [95% CI, 8.8%−12.5%]) and 2013–2014 (20.6% [95% CI, 16.2%−25.6%]; P < .001) as did extreme obesity among children aged 6 to 11 years (3.6% [95% CI, 2.5%−5.0%] in 1988–1994 to 4.3% [95% CI,3.0%−6.1%] in 2013–2014; P = .02) and adolescents aged 12 to 19 years (2.6% [95% CI,1.7%−3.9%] in 1988–1994 to 9.1% [95% CI, 7.0%−11.5%] in 2013–2014; P < .001). No significant trends were observed between 2005–2006 and 2013–2014 (P value range, .09-.87). CONCLUSIONS AND RELEVANCE In this nationally representative study of US children and adolescents aged 2 to 19 years, the prevalence of obesity in 2011–2014 was 17.0% and extreme obesity was 5.8%. Between 1988–1994 and 2013–2014, the prevalence of obesity increased until 2003–2004 and then decreased in children aged 2 to 5 years, increased until 2007–2008 and then leveled off in children aged 6 to 11 years, and increased among adolescents aged 12 to 19 years.

One concern is to what extent the subset of NHANES participants evaluated for HCV infection and diabetes was representative of the entire NHANES population sample. This is a significant question because the overall NHANES sample is considered the best representation of the general population of the United States, a collection of subjects free of the bias usually present in clinic-based investigations. Thus, it was reassuring that the subset of NHANES that could be evaluated for HCV infection and diabetes was both large (9,841 persons) and similar to other NHANES members with respect to many factors, including all recognized correlates of both HCV infection and diabetes. 1 This representation essentially eliminates the potential for selection bias. Another strength of the NHANES analysis is the careful testing for HCV infection performed by the Hepatitis Branch at the Centers for Disease Control and Prevention. Because HCV infection was assessed by second-generation enzyme immunoassay and confirmed by supplemental antibody testing, there is no doubt that most positive results reflect true HCV exposure. Indeed, in the subset tested for both HCV antibody and RNA, HCV RNA was detected in all but 26%, the percent one would expect to have cleared infection if all antibody-positive subjects had been previously infected. 3 Dr. Everhart raised the question of whether the antibody testing should be the main determinant of HCV or if the analysis should be restricted to persons with both HCV antibody and RNA. 2 If one were convinced that the association exists exclusively because ongoing HCV infection caused diabetes, it would have been appropriate to restrict the analysis to persons whose blood contained both HCV antibodies and RNA. Because too little is known about the pathogenesis and temporal sequence of HCV infection and diabetes to make these assumptions, the analysis initially was presented using antibody testing as the marker of HCV exposure. Nonetheless, Dr. Nainan and coworkers at the Centers for Disease Control and Prevention generously provided the HCV RNA data. For the subset for whom there is HCV RNA testing, the age-adjusted odds of type 2 diabetes in persons with HCV RNA and antibody was 2.48 (95% CI 1.23-5.01) compared with 0.98 for persons with HCV antibody but not RNA. If confirmed , these data are not consistent with the conjecture that diabetes leads to HCV infection, but instead favor hypotheses suggesting that persistent HCV infection is associated with the subsequent development of diabetes. Another important discovery in the analysis of HCV infection and type 2 diabetes in NHANES was the difference in the magnitude and direction of the association in persons of relatively young ages. Type 2 diabetes is a clinically heterogeneous syndrome that, according to the Cecil Textbook of Medicine, "typically appears after the age of 40 years." 4 In NHANES III, type 2 diabetes was not associated with HCV infection in persons less than 40 years of age. 1 Type 2 diabetes may be a different condition when it mani...

Nasal colonization with MRSA has increased in the United States, despite an overall decrease in nasal colonization with S. aureus. PFGE types associated with community transmission only partially account for the increase in MRSA colonization.

Many persons in the United States are colonized with S. aureus; prevalence rates differ demographically. MRSA colonization prevalence, although low nationally in 2001-2002, may vary with demographic and organism characteristics.

The seroprevalence of Helicobacter pylori infection was examined in the adult US population and among different ethnic groups. Stored sera from 7465 adult participants in the first phase of the third National Health and Nutritional Examination Survey (1988-1991) were tested with a sensitive and specific IgG ELISA, to diagnose infection. Seroprevalence of H. pylori among all participants was 32. 5%. This increased with age, from 16.7% for persons 20-29 years old to 56.9% for those > or =70 years old. Age-adjusted prevalence was substantially higher among non-Hispanic blacks (52.7%) and Mexican Americans (61.6%) than among non-Hispanic whites (26.2%). After controlling for age and other associated factors, the odds ratios relative to non-Hispanic whites decreased for non-Hispanic blacks, from 3.9 (95% confidence interval [CI], 3.1-4.9) to 3.3 (95% CI, 2. 6-4.2), and for Mexican Americans, from 6.3 (95% CI, 4.8-8.3) to 2.3 (95% CI, 1.6-3.5). The high prevalence of H. pylori infection among non-Hispanic blacks and Mexican Americans is partially explained by other factors associated with infection.

HBV prevalence decreased among US children, which reflected the impact of global and domestic vaccination, but it changed little among adults, and approximately 730,000 US residents (95% confidence interval, 550,000-940,000) are chronically infected.

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