Surveillance Systems

Types of surveillance

The Epidemiology of Obesity
Surveillance and Global Response to SARS An epidemic of severe pneumonia of unknown etiology was detected in Guangdong province, China, in November , and control measures were instituted on the basis of the way the disease spread from person to person. The spread of obesity in a large social network over 32 years. A cannabinoid receptor type 1 CB1R agonist enhance the developmental neurotoxicity of acetaminophen paracetamol. It may be useful to think of the simplicity of a surveillance system from two perspectives: Methods In assessing PVP, primary emphasis is placed on the confirmation of cases reported through the surveillance system.

Definitions and Basic Concepts

Guidelines for Evaluating Surveillance Systems

Partially because of the lessons learned from this epidemic, Uganda has become one of the leading countries in implementing the IDSR program. Surveillance systems are important tools for targeting, monitoring, and evaluating many health risks and interventions.

Because managers need a wide variety of information for specific interventions, systems have been developed and tested to meet those needs. Surveillance for environmental public health practice requires the collection, analysis, and dissemination of data on hazards, exposures, and health outcomes figure Health outcomes of relevance include death, disease, injury, and disability.

However, relating those outcomes to specific environmental hazards and exposures is critical to environmental public health surveillance. Hazards include toxic chemical agents, physical agents, biomechanical stressors, and biologic agents that are located in air, water, soil, food, and other environmental media. Exposure surveillance is the monitoring of members of the population for the presence of an environmental agent, its metabolites, or its clinically inapparent for example, subclinical or preclinical effects.

Four challenges complicate environmental public health surveillance. First, the ability to link specific environmental causes to adverse outcomes is limited by our poor understanding of disease processes, long lead times, inadequate measures of exposure, and multiple potential causes of disease.

Second, data collected for other purposes rarely include sufficient information to meet a case definition for a condition caused by an environmental agent. Third, public alarm is often out of proportion to the hazard of concern, and sentiment will often influence public policy disproportionately to scientific information.

Fourth, biologic markers will become increasingly critical elements of environmental exposure surveillance. Obtaining data on exposure, which can include estimates derived from hazard data through sophisticated modeling or direct measurements of individual exposure obtained from use of personal monitors for example, passive air samplers , is generally impractical in developing countries.

Childhood blood lead levels are the only biomonitoring data that are collected routinely in several countries, either in national surveys or from screening programs for children at high risk. Health outcome surveillance as applied to environmental public health is similar to traditional surveillance efforts.

In the United States, the focus is on surveillance for birth defects; developmental disabilities for example, cerebral palsy, autism, and mental retardation ; asthma and other chronic respiratory diseases for example, bronchitis and emphysema ; cancer; and neurological diseases for example, Parkinson's disease, multiple sclerosis, and Alzheimer's disease McGeehin, Qualters, and Niskar Other nations have different sets of priority conditions for surveillance. Disease registries, vital statistics data, annual health surveys, and administrative data systems for example, hospital discharge data are sources that have been used for monitoring health conditions.

The challenges mentioned previously have constrained our ability in all nations, regardless of level of development, to establish and maintain effective and comprehensive environmental public health surveillance systems. As we invest in understanding the enlarging threats in the global environment, we must overcome these challenges and establish improved surveillance systems. The health of the global community depends on this investment.

Injuries are a major public health problem and are among the 10 leading causes of death worldwide, killing an estimated 5 million persons each year and causing high rates of disability. People from all economic groups are at risk for injuries, but death rates caused by injury tend to be higher in developing countries Peden, McGee, and Sharma Injury surveillance includes monitoring the incidence, causes, and circumstances of fatal and nonfatal injuries.

Injuries are classified by the intention of the act into two groups: If the range of fatal and nonfatal injuries, as well as the risk factors that can lead to injury, are to be fully captured, surveillance systems need to be established in multiple settings.

Fatal injuries can be captured by using forensic or death certificate data. A far greater number of injuries are nonfatal and can be tracked through hospital- or primary care—based systems. Systematic information on nonfatal injuries, including prevalence, incidence, and related risk behaviors can also be obtained through ongoing population-based surveys.

Critical points should be addressed when planning an injury surveillance system in a developing country. First, data sources need to be clarified. In some developing countries, routine data on injuries are not always captured in health information systems. It is therefore necessary to consider other sources of data—for example, law enforcement agencies, coroners, or medical examiners.

Next, the events and variables in an injury surveillance system should be defined according to the objectives of the system. Criteria such as the intentionality violence-related injuries versus unintentional injuries ; the outcome fatal injuries versus nonfatal injuries ; and the nature of violence-related injuries physical, sexual, psychological, deprivation, or neglect should be considered when establishing the system.

Finally, case definitions and coding procedures should be defined before implementing the system. Under the system, a reportable case is defined as a patient who died from or was treated for an injury in the ED. Cases include patients with unintentional and violence-related injuries. ED staff members identify cases and collect data in five hospitals in Nicaragua.

Information used to complete the instrument is collected directly from the patients or their representatives. An ED admission clerk collects basic demographic data on the patient's arrival.

ED medical staff members physicians and nurses collect the remaining information for example, location, mechanism of injury, nature, severity, and circumstances surrounding the injury during triage and assessment. The hospital epidemiologist collects data collection forms daily from the ED, reviews the quality of data, and requests data from the ED staff if the forms are incomplete.

The statistician reviews data daily. The country project coordinator also monitors the quality of the data periodically. Using Epi Info programs developed specifically for this project, the project coordinators analyze trends and identify potential risk factors Noe and others The information is used to produce monthly reports for dissemination. Information is reported at both the regional and the country levels. Injury prevention programs in Nicaragua use surveillance data to assess the need for new policies or programs and to evaluate the effectiveness of existing policies and programs.

For example, the municipality of León is using the information from the hospital to monitor the increase in suicide attempts among youths abusing pesticides and to evaluate an intersectoral campaign to promote life that includes primary through tertiary prevention strategies. Surveillance for biologic terrorism is conducted primarily for outbreak detection and management. Surveillance must support early detection of an incident of biologic terrorism and its characterization in the same manner as for the detection and control of naturally occurring outbreaks of infectious diseases.

Early detection of outbreaks can be achieved by the following Buehler and others Environmental detection systems for microbial pathogens and toxins of concern for biologic terrorism might also be categorized as new types of data early in the course of an outbreak, before infection Meehan and others The primary surveillance tools for event detection and management are the traditional disease-reporting systems for notifiable diseases discussed elsewhere in this chapter.

These core surveillance tools should be robust before new data types can be considered for supplementing public health surveillance. Syndromic surveillance is an investigational approach by which health department staff members, assisted by automated data acquisition and generation of statistical signals computerized algorithms , monitor disease indicators continually to detect outbreaks of disease earlier and more completely than might otherwise be possible with traditional reportable disease methods Buehler and others CDC's list of biologic terrorism agents and diseases can be found at http: The key elements in planning a disaster surveillance system are establishing objectives, developing case definitions, determining data sources, developing simple data collection instruments, field testing the methods, developing and testing the analysis strategy, developing a dissemination plan for the report or results, and assessing the usefulness of the system.

The surveillance needs are different in the preimpact, impact, and postimpact phases Binder and Sanderson The role of surveillance in disaster situations has included the following broad framework of activities:. Support of relief efforts following national and global disasters has been a relatively new application of epidemiologic practice for the public health professionals.

Nevertheless, since the initial CDC involvement with the United Nations in a large-scale relief effort concerning approximately 20 million displaced people affected by the —70 civil war in Nigeria, CDC staff members have participated in several assessments of the health needs, damage, and nutrition in refugee populations resulting from man-made and natural disasters.

The more notable and extended actions were conducted in the —82 Khmer Thailand-Cambodia refugee-relief action, followed by long-term public health surveillance of Somalian refugees —83 , periodic but comprehensive health and nutritional assessments of Afghan refugees in Pakistan — , and growth and nutritional assessments of internally displaced populations—especially children—in the Democratic People's Republic of Korea s and southern Sudan.

Although these relief efforts occurred many years and many thousands of miles apart, they shared several important characteristics:. The major goal of these activities is to identify and eliminate preventable causes of morbidity and mortality. Planning requires effective use of existing knowledge about characteristic or predictable demographic patterns, easily applied health indicators, and avoidable errors of omission or commission.

As in disasters, the principles of surveillance data collection, data analysis, response to data, and assessment of response and other public health techniques should be an integral part of relief efforts. Retrospective evaluation of these efforts has also proved useful CDC Development and evaluation of policies for health improvement require a reliable assessment of the burden of disease and injury, an inventory of the disposition of resources for health, assessment of the policy environment, and information on the cost effectiveness of interventions and strategies.

In all these areas, consideration of noncommunicable mostly chronic conditions becomes critical. In , noncommunicable diseases were estimated to cause approximately 60 percent of the deaths in the world and 43 percent of the global burden of disease WHO a.

WHO forecasts that by the burden of disease from noncommunicable diseases for developing and newly industrialized countries will have increased more than 60 percent Murray and Lopez Some developing countries have found it difficult to acquire and analyze accurate mortality statistics regularly, let alone morbidity and quality-of-life information.

Ensuring development, implementation, and widespread use of noncommunicable disease data for better decisions on resource allocation is critical to improving the quality of lives and promoting a more equitable future for health within and between countries. Hypertension , elevated blood cholesterol, tobacco use, excessive alcohol consumption, obesity, and the multiple diseases linked to these risk factors are a global public health problem.

In one study, smoking, high blood pressure, and high cholesterol alone explained approximately two-thirds to three-fourths of heart attacks and strokes Vartiainen and others Until recently, surveillance for risk factors was an activity commonly associated with developed countries Holtzman However, recently WHO has increased attention to noncommunicable disease surveillance by developing tools and working to achieve data comparability between countries WHO c.

Data on key health behaviors, obesity, hypertension, lipids, and diabetes are collected inconsistently in developing countries, especially in Africa. Data on tobacco use are available through the Global Youth Tobacco Survey http: Incidence data the number and proportion of new cases in a population are limited in developing countries. However, India's National Cancer Registry program may serve as a notable exception http: In , the Indian Council of Medical Research, recognizing that there was a lack of information on follow-up of cancer patients to assess quality of care, instituted a cancer registry network.

The network provides data on the magnitude and patterns of cancer in eight areas of India to enable studies of the histologic features correlating with prognosis and association studies for example, whether a history of vasectomy is associated with cancer of the prostate. Another important example relates to the widespread use of folic acid in China and the resultant reduction in incidence of birth defects Kelly and others ; Wald Surveillance data have been critical in establishing the importance of obesity as a public health priority in the United States.

These data provide a measure of the effectiveness of interventions to meet the control objectives. The BRFSS is a practical tool for developing and middle-income countries, as Jordan demonstrated when it implemented a BRFSS in ; the first survey documented substantial levels of obesity, especially among women, combined with low levels of physical activity CDC b. Public health surveillance is considered a global public good Zacher , particularly when it is used for eradication of such diseases as poliomyelitis.

As eradication campaigns decrease the number of cases, maintaining systems to find the last few cases becomes more expensive. Often, the majority of the costs for these systems fall on hard-pressed developing countries.

This factor raises questions of fairness and equity. For example, as poliomyelitis becomes rare, it ceases to be a significant risk to national populations, whereas other diseases, such as malaria and diarrhea, typically are major causes of morbidity and mortality. In such countries, it seems most fair and efficient for the global community to finance eradication campaigns, leaving national systems free to address the diseases that most affect their populations.

The negative impact of globally mandated eradication surveillance systems can be mediated or reversed by leveraging on the eradication program's infrastructure to gather surveillance data for diseases of concern to local governments Nsubuga, McDonnell, and others A similar case can be made for influenza early warning systems in countries that gather information that will be used to create vaccines that will benefit other populations but not their own.

Equity demands that the countries that benefit from such systems finance them. Public health surveillance systems serve an essential function in preventing and controlling disease spread within and across national borders. Although the private sector benefits, it lacks the incentive to invest in public health surveillance systems, and sovereign states depend on the contribution of others WHO ; this situation has important implications for the financing of public health surveillance systems.

Even within national borders, the difficulty of quantifying the benefits of surveillance systems for individual communities leads to neglect by local authorities, providing the economic rationale for funding by the national government. Developing countries are reportedly the weak link in the global surveillance framework, although they bear the greatest burden of disease, emerging and reemerging old pathogens, and drug-resistant pathogens U.

The greatest need for surveillance systems is in these countries, but most lack both the resources and the political will to build human capacity and finance the systems table Resource constraints and intense pressure to provide care and treatment services lead public health authorities in the poorest countries to spend resources on surveillance U.

Because the costs and benefits derive from surveillance systems spilling across national borders, donors should assist with capacity building in countries that have been unable to invest the human and material resources required.

An interesting and unresolved feature of these global public goods—the solution to their adequate provision and supply rests at local, national, and sometimes regional levels—has prompted the international health community to advocate for capacity building in developing countries rather than for consolidation of the fragmented systems at the global level WHO Standard tools of economic evaluation Meltzer have been used to compare the benefits and costs of several public health interventions.

The public good characteristics of surveillance systems, with benefits that are not easy to quantify, make the use of such tools difficult to implement in practice. However, economic evaluation of laboratory surveillance systems to detect specific disease-causing organisms have been undertaken in the developed world by comparing benefits and costs now and in the future Elbasha, Fitzsimmons, and Meltzer These evaluations have not been done in developing countries and are needed.

At best, an analysis of the benefits and costs of existing or proposed surveillance systems is feasible. This analysis requires an estimate of the cost of illness and answers the question of how many cases of a particular disease need to be prevented by the surveillance system to be exactly equal to the expenditure on the system. Given expenditures on specific health interventions or programs, one can, by using traditional econometric tools, apply the data on health outcomes from the surveillance systems as inputs to economic analysis.

Surveillance also clearly leads to a cost saving if it prevents the need for expenditure on treating patients. Public health agencies, ministries of finance, and international donors and organizations need to transform surveillance from dusty archives of laboriously collected after-the-fact statistics to meaningful measures that provide accountability for local health status or that deliver real-time early warnings for devastating outbreaks.

This future depends in part on developing consensus on critical surveillance content and developing commitment on the part of countries, funding partners, and multilateral organizations to invest in surveillance system infrastructure and to use surveillance data as the basis for decision making. This vision of the future assumes a coherent, integrated approach to surveillance systems that is based on matching the surveillance objective with the right data source and modality and on paying attention to country-specific circumstances while maintaining global attention to data content needs.

Information technology and informatics can help in attaining this vision. Specifically, technology can facilitate the collection, analysis, and use of surveillance data, if data standards are developed and compatible systems are established.

Data collection for surveillance would be an automatic by-product of any electronic systems used to support clinical care. Under this scenario, an automatic electronic message would be sent to the responsible public health jurisdiction with information about a health event for example, death, disease, or injury , including all relevant information from the electronic health record about the patient, provider's name, patient's home address, risk factors, previous immunizations, and treatments.

Even before this ideal capacity becomes widespread, technology such as cell phone—based systems could accelerate collection of key data for example, occurrence of a viral hemorrhagic fever outbreak. The rapid penetration of cell phones in developing countries might obviate the need for prohibitively expensive landline-based systems.

An accelerated system of wireless Internet access might also transform the capacities to which a local health post or a district health official might have access. These systems should also be considered as means for collecting information beyond traditional data. For example, telemedicine access can permit views of a rash illness to be shared with national or international medical specialists.

Analysis of surveillance data can also be transformed by using available technology. Software that is Web-enabled, together with the advances in geographic information system software and global positioning devices, means that anyone with Internet access can potentially apply the latest version of software running on a distant server in the national capital to local data to generate up-to-date maps and graphs describing health status in that jurisdiction.

Use of surveillance data can also be transformed. Sophisticated algorithms can be applied to data as it is collected to determine when and how an alert should be sent to local, national, or even international health officials to indicate a need for immediate investigation.

Increasingly sophisticated visual display techniques and creation of custom channels with data of particular relevance to groups of data users are just some of the tools already being used to put public health content on the desktop of anyone with broadband, secure Internet access.

Realization of this future vision does not require technology beyond what is already feasible, but the following factors are needed:. Globally, infectious disease surveillance is implemented through a loose network that links parts of national health care systems with the media, health organizations, laboratories, and institutions focusing on particular disease conditions.

WHO has described a "network of networks" U. GAO that links existing regional, national, and international networks of laboratories and medical centers into a surveillance network figure Military networks, such as the U. The network has more than partners around the world and identifies and responds to more than 50 outbreaks in developing countries each year Heymann and Rodier The International Health Regulations are the only binding international agreements on disease control.

The regulations provide a framework for preventing the international spread of disease through effective national surveillance coupled with the international coordination of response to public health emergencies of global concern by using the guiding principle of maximum protection, minimum restriction WHO a.

The current regulations apply only to cholera, plague, and yellow fever; they require WHO member states to notify WHO of any cases of these diseases that occur in humans within their territories and then give further notification when the territory is free of infection. The regulations are being revised to include the development of national core capacities and national focal persons who have the competencies of graduates of FETPs and allied training programs. Programs established to improve the capacity of both epidemiologists and laboratorians to collect, use, and interpret surveillance and outbreak data for example, the collaborative WHO program in foodborne diseases called the WHO Global Salm-Surv are also important components in developing global surveillance networks.

Developing nations share surveillance needs with the rest of the world, yet they are challenged by economic limitations, weak public health infrastructure, and the overwhelming challenges of poverty and disease.

As a result, countries in the developing world often depend on the research efforts of others, or they collaborate with others to conduct the research necessary for their surveillance needs. Within individual countries, surveillance systems are essential in measuring disease and injury burden as a first step in establishing public health priorities that lead to policies and programs.

The major research question for surveillance is how to develop and maintain a cadre of competent, motivated surveillance and response workers in developing countries. Other questions include how to design and maintain surveillance systems for these problems, especially morbidity systems for chronic diseases.

Standard methods can be used to evaluate existing surveillance systems, which, in turn, will help define surveillance needs Romaguera, German, and Klaucke Developing countries have used the IDSR strategy, which provides an efficient approach to data collection and analysis. Unfortunately, the majority of developing countries have limited surveillance systems for noninfectious diseases; instead, existing data systems for example, vital records, motor vehicle crash records, or insurance claims data are potential sources of surveillance data.

In other settings, even these data sources are scarce, and approaches such as verbal autopsies and recurrent surveys might be alternatives White and McDonnell Surveillance for risk factors is another challenge, and BRFSSs need to be validated and applied more widely in developing countries.

Surveillance for injuries, environmental hazards such as traffic intersections that are associated with high rates of injuries , and exposures to chemical or biological agents is a key public health concern with few examples of effective application anywhere in the developed or less developed parts of the world.

Rigorous research is required in this field Thacker and others The burgeoning use of electronic data systems and the almost universal availability of the Internet provide a tremendous opportunity for more timely and comprehensive surveillance in all parts of the world.

This section provides background information understanding and comparing the various physical activity surveys. National Immunization Survey NIS This nationwide survey provides current national, state, and selected urban-area estimates of vaccination coverage rates for U.

Infant Feeding Practices Survey II CDC is collaborating with researchers from the Food and Drug Administration to conduct this nationwide longitudinal study which focuses on infant feeding practices and the diets of women from their 3rd trimester to 12 months postpartum. Maternity Care Practices Survey mPINC CDC has developed a survey of all labor and delivery service facilities in the United States in an effort to monitor maternity care practices associated with successful breastfeeding promotion and support.

This systematic data collection of nationwide breastfeeding-related maternity care practices occurs every other year; the first survey was carried out in , the second in HealthStyles Survey Healthstyles is a private proprietary national marketing survey that annually collects health-related opinions of men and women aged 18 years and above.

Because Healthstyles includes a large, demographically diverse sample of the U. CDC has contributed breastfeeding questions to the survey since In children aged 6—9 years, the combined prevalence was higher in urban than in rural areas Among adolescents aged 10—18 years, whereas the combined prevalence was slightly higher in rural than in urban areas A recent study based on the Add Health study — baseline data examined the differences in US adolescents' risk of obesity and in their physical activity patterns according to neighborhood characteristics Study participants were grouped into six categories: Compared with US adolescents living in newer suburbs, those living in rural working-class, exurban, and mixed-ethnicity urban areas were approximately 30 percent more likely to be overweight, independent of individual SES, age, and ethnicity.

These findings illustrate important effects of the neighborhood on health and the inherent complexity of assessing residential landscapes across the United States. Simple classic urban-suburban-rural measures may mask the important complexities. Unlike for adults, and because national guidelines for classifying central obesity are lacking, little is known about the status of central obesity in US children and adolescents.

In fact, compared with their counterparts, Mexican-Americans boys and non-Hispanic Black girls aged 18 years had the highest waist circumference values in the 90th percentile Ethnic differences in waist circumference cm and gender, age-, and ethnicity-specific percentiles among US children and adolescents, National Health and Nutrition Examination Survey III, — In the two keys, ages are given in parentheses.

A large number of studies have shown the tracking of BMI and obesity status from childhood to adulthood 62—67 , providing additional support for early prevention.

Overall, it is estimated that about one third of obese preschool children and about one half of obese school-age children become obese adults, although findings from different studies varied considerably. For example, when longitudinal data collected from 2, children initially aged 5—14 years over 17 years from childhood to adulthood were used 62 , the tracking of childhood BMI was stronger in Blacks than in Whites.

Among overweight children, 65 percent of White girls versus 84 percent of Black girls became obese adults; among boys, the corresponding figures were 71 percent versus 82 percent.

Projections based on these models indicate that by , the prevalence of obesity among adults will reach The projection is even more alarming for the prevalence of overweight. Overall, the prevalence will be In some of the projections, the last available data were for the period — These projections include adult, gender-specific obesity for all ethnic groups, and adult gender-specific overweight for each ethnic group and all ethnic groups.

A similar pattern is observed for adolescents aged 12—19 years. Currently, more than two thirds of US adults and approximately one third of US children and adolescents are overweight or obese, and some minority and low-SES groups are disproportionally affected. The prevalence of obesity and overweight among US children and adults has more than doubled since the s, and the rate continues to rise.

Numerous studies have shown that obesity increases morbidity and mortality Obesity has become the second leading preventable cause of disease and death in the United States, second only to tobacco use 1.

Obesity is likely to continue to increase and soon become the leading cause if no effective approaches to controlling it can be implemented. On the other hand, some minority groups such as Asian Americans have a lower prevalence of obesity. Of great concern, our analysis shows that the prevalence of obesity and overweight has increased at an average annual rate of approximately 0. If a similar increase in trend is assumed, by , the majority of US adults 75 percent: Some population groups will be more seriously affected.

For example, by , However, current available data are limited and do not enable us to examine the trends in other minority groups or to understand the factors that have led to the current obesity epidemic. A good understanding of underlying causes that triggered the increase in obesity prevalence in the United States over the past three decades and the factors that have contributed to the disparities across groups is critical in fighting this growing public health crisis and achieving an important national priority to eliminate health disparities.

Although obesity is caused by many factors, in most persons, weight gain results from a combination of excess calorie consumption and inadequate physical activity. To maintain a healthy weight, there must be a balance between energy consumption through dietary intake and energy expenditure through metabolic and physical activity A number of individual-, population-, and international-level factors and environmental determinants might have played a role in the obesity trends, such as changes in people's eating behaviors, physical activity and inactivity patterns, occupation, development of technology, culture exchange, and global trade 16 , 17 , The NHANES data show a dramatic increase in the prevalence of overweight and obesity across all population groups and a declining disparity of obesity across SES groups over the past two decades.

This finding indicates that individual characteristics are not the dominant factor to which the rising obesity epidemic is ascribed. Social environmental factors might have a more profound effect in influencing individuals' body weight status than do individuals' characteristics such as SES. A growing consensus is that environmental factors have played a pivotal role in influencing people's lifestyles and fueling the obesity epidemic in the United States and worldwide 17 , 68 , The current society provides Americans with abundant food at a relatively low cost and numerous opportunities to reduce energy expenditure at work and at home, which facilitates sedentary behaviors.

Nationally representative survey data examining trends in people's eating patterns between and the s have indicated several patterns likely to put people in the United States at increased risk of obesity, such as increased consumption of total energy, soft drink, and snack foods; more frequent eating at fast-food and other restaurants; and inadequate consumption of vegetables and fruits compared with dietary recommendations 70— The increase in portion size in the United States over the past three decades probably is an important contributor to overconsumption of food and has fueled the growing obesity epidemic.

Although our current understanding of the underlying complex causes of the disparities in obesity between population groups in the United States e. At the community level, disadvantage may constrain people's ability to acquire and maintain healthy diet and exercise behaviors. Differential rates of available local area physical fitness facilities, restaurants, and types of food stores by neighborhood characteristics may help explain why obesity does not affect all population groups equally 79 , A recent study shows significant disparities in the availability of food stores.

African-American and Hispanic neighborhoods had fewer chain supermarkets compared with White and non-Hispanic neighborhoods, by about 50 percent and 70 percent, respectively The availability of supermarkets has been associated with more healthful diets, higher vegetable and fruit consumption, and lower rates of obesity 82 , Shopping at supermarkets versus independent groceries has been associated with more frequent vegetable and fruit consumption The Add Health study shows that lower-SES and minority population groups had less access to physical activity facilities, which in turn was associated with decreased physical activity and increased overweight Population-based policies and programs that emphasize environmental changes are most likely to be successful.

Strategies to tackle obesity need to be incorporated into other existing health promotion programs, particularly those preventing chronic diseases by promoting healthful eating and physical activity. Childhood and adolescence are key times for persons to form lifelong eating and physical activity habits. Overweight children are likely to remain obese as adults.

Thus, obesity prevention in schoolchildren is a public health priority. In addition, because the majority of children spend many of their waking hours in schools, schools should be key partners in the prevention of childhood obesity.

It is crucial to tailor treatment and prevention efforts to each particular ethnicity group's specific situation and needs. Government agencies, industry, public health professionals, and individual persons all need to play an active role in the growing national efforts to combat the obesity epidemic.

The surveys were designed by using stratified multistage probability samples. In each survey, standardized protocols were used for all interviews and examinations. Data on weight and height were collected for each person through direct physical examination in a mobile examination center. Recumbent length was measured in children younger than age 4 years and stature in children aged 2 years or older. BRFSS is the world's largest ongoing telephone health survey system, tracking health conditions and risk behaviors in the United States yearly since Conducted by the 50 state health departments as well as those in the District of Columbia, Puerto Rico, Guam, and the US Virgin Islands, with support from the Centers for Disease Control and Prevention, this system uses standard procedures to collect data through a series of monthly telephone interviews with US adults.

BRFSS provides state-specific information about issues such as obesity, asthma, diabetes, health care access, alcohol use, hypertension, cancer screening, nutrition and physical activity, and tobacco use; that is, it enables geographic differences to be examined The YRBSS was developed in ; the first survey was started in to monitor priority health risk behaviors that contribute markedly to the leading causes of death, disability, and social problems among youth and adults in the US.

YRBSS collected information on risk behaviors e. Add Health is a nationally representative, school-based study of youths grades 7—12, approximately aged 12—17 years followed up with multiple interview waves into young adulthood approximately aged 18—26 years. The study used a multistage, stratified, school-based, clustered sampling design.

A stratified sample of 80 high schools and feeder middle schools was selected with probability proportional to size. Wave I — included 20, adolescents aged 12—19 years and their parents. Wave II included 14, wave I adolescents including school dropouts and excluding graduating seniors. Wave III — included 15, wave I adolescents, now aged 18—26 years and entering the transition to adulthood 76 percent response rate. In waves I and II, information on self-reported weight and height, and in wave III direct measured weight and height, was collected.

Some other studies published since the early s have also examined the complex relation between gender, ethnicity, SES, and obesity among US adults and children. For example, earlier data collected in the CARDIA study from 5, Black men and women and White men and women aged 18—30 years suggested that the association of education with obesity was negative among White women and positive among Black men, with no significant association noted among White men and Black women Another study assessed the contribution of SES in explaining ethnic disparities in obesity among adult women; it concluded that Black ethnicity was an independent SES risk factor for obesity However, patterns of obesity were shown to differ by educational attainment within ethnic groups, which has implications for the segmentation of risk reduction programs When Whites were compared with Hispanics, a matched-pair design study found the highest prevalence of overweight among the least educated Hispanic women In a multiple regression model, the higher body mass index levels of Hispanic women and men relative to their White counterparts were not explained by age, gender, education, city of residence, time of survey, or language spoken A study of cardiovascular disease risk factors, including obesity, based on several national surveys found that for men, the highest prevalence of obesity Black women with or without a high school education had a higher prevalence of obesity Another study showed that socioeconomic deprivation in childhood was a strong predictor of adulthood obesity in African-American women, and the findings were consistent with both critical-period and cumulative-burden models of life-course socioeconomic deprivation and long-term risk for obesity Regarding young people, the — baseline data from the Add Health study show that overweight prevalence decreased with increasing SES among White females and remained elevated and even increased among higher SES African-American females.

Among males, disparity was lowest at the average SES level The Growth and Health Study of the National Heart, Lung, and Blood Institute collected data from younger children aged 9—10 years and showed that higher-SES White girls had a lower prevalence of obesity, but there was no clear relation among Black girls Another study of a nationwide sample of preschool children drawn from 20 large US cities showed that the higher prevalence of obesity among Hispanics relative to Blacks and Whites was not explained by ethnic differences in maternal education, household income, or food security A study compared current portions of food products in the United States with past portions, concluding that the sizes of current marketplace foods almost universally exceed those offered in the past.

The trend toward larger portion sizes in the United States began in the s, and portion sizes increased sharply in the s and have continued to increase. Study results show that, except for sliced white bread, all of the commonly available food portions exceeded the US Department of Agriculture and Food and Drug Administration standard portions, sometimes to a great extent.

For example, the largest excess over US Department of Agriculture standards by percent occurred in the cookie category, while cooked pasta, muffins, steaks, and bagels exceeded standards by percent, percent, percent, and percent, respectively.

For french fries, hamburgers, and soda, the current portion sizes are 2—5 times larger than in the past The influence of growing portion size on people's energy intake is magnified by the fact that more people in the United States increasingly eat meals away from home more often than they did in the past Dietary intake data collected from individuals also support a marked trend toward larger portion sizes in the United States. Based on nationally representative data collected between and , a study reported that the portion sizes of food consumed both at home and outside the home had increased for a large number of foods.

Some of the increases were substantial, very often ranging between 50 kcal and kcal per item for commonly consumed food items such as salty snacks, soft drinks, hamburgers, french fries, and Mexican food. The potential impact of larger portion sizes on people's overconsumption of energy and weight gain can be remarkable. For example, an added 10 kcal per day of extra calories can result in an extra pound 0. The authors thank Drs. Oxford University Press is a department of the University of Oxford.

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Introduction