Question: What is BMI?
Answer: BMI, or body mass index, is a widely accepted screening tool for identifying overweight and obese individuals who may be at risk for weight related health problems. It is calculated from a person’s height and weight. To control for differences in body sizes due to gender and age, BMI values for children are commonly expressed in percentiles. A child with a BMI percentile above the 95th percentile is considered obese.
Question: Is BMI screening always accurate? Are all children with a high BMI actually overweight or obese?
Answer: No. BMI is a screening test and not a diagnosis of overweight or obesity. A diagnosis of overweight or obesity can only be made by a trained clinician based on assessment of other risk factors.
Question: Is BMI an accepted measurement for screening for obesity and overweight?
Answer: Yes, BMI is widely accepted as a reliable and valid tool for assessing overweight in children. The American Academy of Pediatrics (Barlow & and the Expert Committee, 2007) and the U.S. Preventive Services Task Force (Klein et al., 2010) recommend annual BMI screening for all children and adolescents.
Question: Why is BMI needed? Why is it important to determine if children are overweight at an early age?
Answer: Prevention of obesity in childhood is likely to be more effective than medical treatment for obesity in adulthood (Committee on Nutrition, 2003). Overweight children have a 70 percent chance of becoming overweight as adults (Nader et al., 2006) and health problems from overweight can begin even in childhood.(Van Cleave, Gortmaker, & Perrin, 2010)
Question: What is the difference between BMI screening and BMI surveillance?
Answer: BMI is used as a screening test to identify whether individual children are at risk for overweight or obesity. When screening tests identify children with high BMI values, they should be referred to a clinician to determine whether their weight puts them at risk for weight-related health problems. BMI is used as a surveillance tool when data on large groups of children are pooled for analysis to determine broad obesity trends in a population. It does not matter for surveillance purposes that some children may have a high BMI but not have weight-related health risks. Surveillance studies are not concerned with the identities of specific children.
Question: Why does the government need my child’s BMI information?
Answer: BMI data from your child, when grouped with many other children’s BMI data, can inform public health officials’ efforts to control one of the most costly public health problems our country faces. These surveillance data can help experts determine the rate of childhood obesity in a specific community, when and where to launch new prevention efforts, how to best plan these programs around a community’s specific needs, when to seek policy changes, and how to evaluate efforts undertaken to confront the obesity epidemic.
Question: Is it better to do BMI surveillance in schools or doctors’ offices?
Answer: This is currently a topic of debate. Schools have the advantage of having access to most all children ages 5-17 and already conduct other health screenings, such as vision tests and scoliosis checks. Arkansas has successfully screened school children for obesity for several years with no major concerns about privacy or stigma. Doctors, by contrast, see children most commonly during the youngest ages (where obesity prevention is a priority). Because health professionals are already weighing and measuring large numbers of children routinely, and because they are experts at assessing and treating weight-related risks that individual overweight or obese children may have, data collected in clinics can be used for both screening and surveillance.
Question: Do I need to be worried about the government having data on my child?
Answer: Privacy concerns are understandable, but often overestimated. City, state, and federal governments all over the world have been collecting public health data for the last few centuries and the risk of surveillance data being misused is very small. Methods and standards developed over decades of data surveillance ensure that data are combined and stripped of identifying information at every opportunity, and strict limits are placed on who has any access to data that might be identifiable. Modern electronic surveillance methods are actually more secure than traditional paper-based methods, and excellent methods have been developed to ensure patient privacy.
Question: What other health information does the government already collect in data surveillance efforts, and how is it used?
Answer: Over the last two centuries, public health surveillance data helped track, prevent, and even eradicate common infectious diseases. Putting these data in the hands of public health experts has resulted in major advances in the prevention of death and disease and longer life expectancies for Americans. As examples, states are required to report to the federal government every case of more than 40 diseases ranging from anthrax to yellow fever. As infectious diseases have become better controlled, chronic diseases have become the leading causes of death and disease. Regular surveys now track both risky behaviors such as smoking and drug use among youth, as well as healthy behaviors such as the use of seat belts and bicycle helmets.
Question: How does the government use health surveillance information?
Answer: Public health officials review this information to look for new patterns of risk factors or diseases, or to detect and contain outbreaks of known diseases. For effective prevention or treatment of any disease or condition, it is essential that we learn the magnitude of a problem, where and in whom it is being found, its causes, and the effectiveness of treatments used so that we can develop ways to prevent the further spread of illness. For example, surveillance data let health authorities know if contaminated food or medication needs to be recalled, if pools or beaches need to be cleaned or closed due to either contamination from chemicals or bacteria, whether environmental contaminants need to be removed or avoided, or how long students need to stay home to prevent spreading an illness. The knowledge that diseases were becoming resistant to antibiotics due to overuse was gained through health surveillance activities.
Question: What are some examples of new diseases or conditions health authorities learned about based on health surveillance data?
Answer: Health surveillance information has been critical in learning about a wide range of diseases that are a serious threat to public health. Just a few examples from the last 30 years include toxic shock syndrome, West Nile virus, Lyme disease, H1N1 flu, and Legionnaires Disease.
Question: Is surveillance only used for contagious diseases?
Answer: No, health surveillance data also tracks accidents and preventable diseases, as well as risky and healthy behaviors. For example, surveillance data have demonstrated that reductions in smoking and drunk driving have resulted from policy changes and have lead to fewer deaths from certain forms of cancer and auto accidents. Based on surveillance data, it has also been possible to determine that laws to require use of booster seats and bicycle helmets have been effective at reducing deaths from vehicle accidents.
Question: Can you give an example of a time where the government has used surveillance information to successfully tackle a health problem?
Answer: A bigger challenge would be identifying a health problem that was effectively dealt with in the absence of quality surveillance data.
One example, among many, is related to government efforts to prevent and reduce one of the leading causes of death in the U.S.: traffic injuries. The Fatal Accident Reporting System (FARS) collects many pieces of data from every crash scene that results in a death on our roadways. Over 30 years, data from this system has led to the development and adoption of consumer product standards (e.g., airbags and seatbelts), engineering and environmental improvements (e.g., rumble strips and lane dividers), and policies (e.g., helmet laws and drunk driving penalties) that have all reduced injuries and deaths. As a result, road fatalities have decreased dramatically even though Americans are driving more miles than ever before.
Another example demonstrates how surveillance data have been used to contain an epidemic. Although measles practically disappeared in the U.S. after the vaccine was introduced in 1963, periodic outbreaks have continued to appear. During the first seven months of 2008, 131 cases were reported in 15 states, more than double the number of cases in 2006-7 combined. Surveillance efforts determined that few of the individuals afflicted in 2008 had been vaccinated and that nearly all of the cases could be traced back to just 17 people who had been exposed to measles in other countries. Using this information, public health officials were able to alert susceptible individuals to the risk of infection and about methods to prevent additional spread. Thanks to these efforts, fewer than a dozen additional cases were reported during the rest of 2008.
Further information about the privacy of surveillance data is at:
http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5017a1.htm
http://www.cdc.gov/vaccines/programs/iis/pubs/downloads/cir-manual/cirman2.pdf
http://www.immregistries.org/know/standards.phtml
Sources
Committee on Nutrition. (2003). Prevention of Pediatric Overweight and Obesity. Pediatrics, 112(2), 424-430. doi:10.1542/peds.112.2.424
Nader, P. R., O'Brien, M., Houts, R., Bradley, R., Belsky, J., Crosnoe, R., Friedman, S., et al. (2006). Identifying risk for obesity in early childhood. Pediatrics, 118(3), e594-601.
Van Cleave, J., Gortmaker, S. L., & Perrin, J. M. (2010). Dynamics of Obesity and Chronic Health Conditions Among Children and Youth. JAMA, 303(7), 623-630. doi:10.1001/jama.2010.104