Obsesidade e sobrepeso nos EUA: Pesquisa revela quadro grave: 68 por cento da população
13/4/2010
Fonte: The Journal of the American Medical Association
Importante tal artigo para os estudiosos do tema Pol¨ªticas p¨²blicas, publicado in The Journal of the American Medical Association:
Prevalence and Trends in Obesity Among US Adults, 1999-2008
Katherine M. Flegal, PhD; Margaret D. Carroll, MSPH; Cynthia L. Ogden, PhD; Lester R. Curtin, PhD
JAMA. 2010;303(3):235-241. Published online January 13, 2010 (doi:10.1001/jama.2009.2014).
ABSTRACT
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.
INTRODUCTION
The National Health and Nutrition Examination Survey (NHANES) provides the opportunity to track trends in the prevalence of obesity in the United States by collecting data on height and weight measurements. Data from 1988-1994 showed that the prevalence of obesity in adults had increased by approximately 8 percentage points in the United States since 1976-1980, after being relatively stable over the period 1960-1980.1-2 Analyses of data from 1999-2000 showed further increases in obesity for both men and women and in all age groups.3
The increases in obesity from 1976-1980 to 1988-1994 were statistically significant in all sex and age groups. The increases in obesity from 1988-1994 to 1999-2000 were statistically significant in all sex and age groups except men aged 40 to 59 years. Analyses of data from 2001-2002 and 2003-2004 suggested increasing trends since 1999-2000 among men but not among women.4-5 Comparisons between 2003-2004 and 2005-2006 showed no significant changes but had limited statistical power.6
Herein we report the results from the latest NHANES data from 2007-2008 regarding population trends in obesity and compare the results over the 10-year period from 1999 through 2008.
METHODS
The NHANES program of the National Center for Health Statistics, Centers for Disease Control and Prevention, includes a series of cross-sectional, nationally representative health examination surveys beginning in 1960. To obtain a nationally representative sample of the US civilian noninstitutionalized population, each survey period used a complex, stratified, multistage probability cluster sampling design. Beginning in 1999, NHANES became a continuous survey (without a break between cycles) and data are released in 2-year cycles, including 1999-2000, 2001-2002, 2003-2004, 2005-2006, and 2007-2008.
In 2007-2008, the sample consisted of 8082 men and women aged 20 years or older; of whom 73.4% (n = 5935) were interviewed and 70.6% (n = 5707) were both interviewed and examined. Participants missing weight or height measurements (n = 95) and pregnant women (n = 57) were excluded from the analyses. This report uses data for 2750 adult men and 2805 nonpregnant adult women with measured weights and heights from the most recent 2 years of the continuous NHANES 2007-2008, in addition to data from NHANES 1999-2006. NHANES 1999-2008 received approval from the National Center for Health Statistics research ethics review board. Written informed consent was obtained.
Weight and height were measured in a mobile examination center using standardized techniques and equipment. Body mass index (BMI) was calculated as weight in kilograms divided by height in meters squared, rounded to the nearest tenth. For adults aged 20 years or older, overweight was defined as a BMI of 25.0 to 29.9 and obesity was defined as a BMI of 30.0 or higher.7 Obesity may be divided into grade 1 (BMI, 30-<35), grade 2 (BMI, 35-<40), and grade 3 (BMI 40).8
Individuals were grouped by age at the interview: 20-39 years, 40-59 years, and 60 years or older. Race and ethnicity were self-reported; for the purposes of this report, race and ethnicity are classified as non-Hispanic white, non-Hispanic black, Mexican American, other Hispanic, and other. Data for 2007-2008 are presented overall, including all racial and ethnic groups, and separately for non-Hispanic white, non-Hispanic black, all Hispanics (including both Mexican Americans and other Hispanics) and Mexican Americans. In 2007-2008, non- Hispanic blacks and Hispanics were oversampled to provide adequate sample sizes for analyses of these groups. In surveys from 1999 through 2006, Mexican Americans but not all other Hispanics were oversampled, so trends are examined for Mexican Americans rather than for all Hispanics.
Statistical analyses were performed using SAS software version 9.2 (SAS Institute Inc, Cary, North Carolina) and SUDAAN software version 10.0 (RTI, Research Triangle Park, North Carolina). Calculation of sampling weights took into account unequal probabilities of selection resulting from the sample design, nonresponse, and noncoverage. All analyses took into account differential probabilities of selection and the complex sample design. Standard errors were estimated with SUDAAN software using Taylor series linearization. Statistical tests were 2-sided and a P value of less than .05 was considered statistically significant.
Linear trends over the five 2-year survey cycles and variations in the prevalence of obesity by age and racial and ethnic groups over the 10-year period were tested using sex-specific logistic regression models with adjustment for age group, racial and ethnic group, and survey period; survey was treated as a continuous (ordered categorical) variable.
Approximate power calculations were performed using POWER software version 3 (National Cancer Institute, Bethesda, Maryland), assuming a survey design effect of 2. These calculations indicated that the sex-specific sample sizes were adequate to detect an odds ratio (OR) equivalent to an increase of 5 percentage points between 1999-2000 and 2007-2008 with 80% power and an OR equivalent to an increase of 6 percentage points with greater than 90% power.
In addition, sex-specific logistic regression models were fitted that included survey as a categorical variable, with adjustment for age group and racial and ethnic group. Logistic models with survey as a continuous variable were fitted within sex, age, and racial and ethnic subgroups. For graphical presentation only, the frequency distributions of BMI were smoothed using a 4253 H nonparametric smoothing algorithm, based on sequential calculations of running medians for groups of adjacent points.9
RESULTS
Sample sizes for analyses from 2007-2008 are presented in Table 1. Detailed information on the prevalence of obesity (BMI 30) and of overweight and obesity combined (BMI 25) overall and by age, sex, and racial and ethnic group from NHANES -2008 is presented in Table 2.