摘要：Objectives. We determined current trends and patterns in overweight, obesity, and extreme high obesity among Pennsylvania pre-kindergarten (pre-K) to 12th grade students and simulated future trends. Methods. We analyzed body mass index (BMI) of pre-K to 12th grade students from 43 of 67 Pennsylvania counties in 2007 to 2011 to determine trends and to discern transition patterns among BMI status categories for 2009 to 2011. Vinsem simulation, confirmed by Markov chain modeling, generated future prevalence trends. Results. Combined rates of overweight, obesity, and extreme high obesity decreased among secondary school students across the 5 years, and among elementary students, first increased and then markedly decreased. BMI status remained constant for approximately 80% of normal and extreme high obese students, but both decreased and increased among students who initially were overweight and obese; the increase in BMI remained significant. Conclusions. Overall trends in child and adolescent BMI status seemed positive. BMI transition patterns indicated that although overweight and obesity prevalence leveled off, extreme high obesity, especially among elementary students, is projected to increase substantially over time. If current transition patterns continue, the prevalence of overweight, obesity, and extreme high obesity among Pennsylvania students in 2031 is projected to be 16.0%, 6.6%, and 23.2%, respectively. The economic consequences of obesity in the United States were estimated at $147 billion annually in 2008. 1 To better understand these costs, obesity trends to the year 2030 were predicted. 2 Obesity prevalence could reach 51% by 2030, but is more likely to stay at more than 40% because of recently emerging positive developments. A subcategory, severe obesity, that is, body mass index (BMI; defined as weight in kilograms divided by the square of height in meters) of 40 or greater for adults, has increased faster than overall obesity and is projected to grow from 5% of adults in 2010 to 11% of adults by 2030. 2 This growth, with its attendant increased risks of disease, will escalate costs even if overall obesity prevalence stabilizes. 2 Because obesity rates vary across states, the financial burden is not uniform. 3 State-specific differences, such as lower cost of less healthy foods, can affect obesity and severe obesity prevalence together with current and projected health care costs. 2 Because of the state-specific nature of Medicaid and Medicare expenditures, much of the high cost of obesity-related disease is borne by public sector health plans. Today’s children and adolescents will be the youngest adults in 2030; therefore, obesity prevention for the future requires monitoring of obesity prevalence rates among this population over time. Prevalence and trends in obesity among US children from 1999 to 2010 were determined based on National Health and Nutrition Examination Survey data. 4 Prevalence of high BMI in US children and adolescents has also been studied. 5 By 2010, fewer than 12% of those aged 2 to 19 years nationwide were at or above the 97th percentile (extreme high obese [ExHi obese]); 17% were above the 95th percentile (obese), and 32% were above the 85th percentile (overweight). A statistically significant increase among 6- to 19-year-old males with a BMI at or above the 97th percentile was found between 1999 and 2008. 4 To inform prevention efforts, state governments have a vested interest in monitoring obesity prevalence among all age groups, and especially among children and adolescents. Pennsylvania, for example, mandates annual height and weight screening with BMI calculation for all public school students statewide. 6 One recent study assessed child and adolescent BMI trends in Pennsylvania, excluding Philadelphia and surrounding counties, for 2005 to 2009 7 and found combined overweight and obese rates decreased from 28.5% to 23.1% at the middle school level and from 24.6% to 20.9% at high school levels, but increased from 10.9% to 20% at the elementary level. The largest shift in BMI over the subset of years from 2007 to 2009 was among overweight elementary students; 58% of those who were overweight in 2007 were obese in 2009. Overweight and obese increased for the study population as a whole because of this sharp increase among elementary students. In a second, separate study, 8 trends in obese (BMI ≥ 95th percentile) and ExHi obese (defined 8 as BMI ≥ 35 kg/m2) among 5- to 18-year-old students attending Philadelphia schools in 2006 to 2010 were determined; obesity across all ages decreased from 21.5% to 20.5% and ExHi obese from 8.5% to 7.9%. Obese and ExHi obese were most prevalent among middle school students, Hispanic boys, and Black girls. 8 The purpose of our study was to determine prevalence, trends, and patterns in overweight, obese, and ExHi obese among Pennsylvania school children. Specific research questions were: What were the prevalence and trends in overweight, obese, and ExHi obese from 2007 to 2011 among elementary, middle, and high school students? What movement patterns, if any, occurred in normal weight, overweight, obese, and ExHi obese among Pennsylvania elementary, middle, and high school students from 2009 to 2011? If current patterns continue, what percentage of children and adolescents would be overweight, obese, and ExHi obese in 2030?
