KEY TERMS
Behavioral Risk Factor Surveillance Survey (BRFSS)
Core functions of public health
Just as a doctor monitors the health of a patient by taking vital signs—blood pressure, heart rate, and so forth—public health workers monitor the health of a community by collecting and analyzing health data. These data are called health statistics. Statistics are a vital part of public health’s assessment function, used to identify special risk groups, to detect new health threats, to plan public health programs and evaluate their success, and to prepare government budgets. The statistics collected by federal, state, and local government are the raw material for research on epidemiology, environmental health, social and behavioral factors in health, and for the medical care system.
At the federal level, the primary agency that collects, analyzes, and reports data on the health of Americans is the National Center for Health Statistics (NCHS), part of the Centers for Disease Control and Prevention (CDC). The NCHS collects its data in two main ways: First, states periodically transmit data they have compiled from local records; vital statistics, including virtually all births and deaths, are routinely collected this way. Second, the NCHS conducts periodic surveys of representative samples of the population, seeking information on certain characteristics such as health status, lifestyle and health-related behavior, onset and diagnosis of illness and disability, and the use of medical care. Some of these surveys are conducted on a state-by-state basis, and the data are thus useful to states and local communities. In addition, other federal agencies that collect data for their own purposes share it with the NCHS.
Vital Statistics
Births and deaths are the most basic, reliable, and complete data collected. Virtually every birth and death in the United States is recorded on a birth certificate or death certificate. Certificates are filed with the local registrar by the attending physician, midwife, undertaker, or other attendant. The state health department is generally responsible for collecting these reports and transmitting them periodically to the NCHS.
Birth certificates contain information supplied by the mother about the child’s family, including names, addresses, ages, race and ethnicity, and education levels. Medical and health information is supplied by the hospital, doctor, or other birth attendant concerning prenatal care, birth weight, medical risk factors, complications of labor and delivery, obstetrical procedures, and abnormalities in the newborn. In the past decades many states have added a question on the mother’s use of tobacco to the birth certificate. Much of the information on the certificate is confidential, withheld even from the person represented by the certificate. Its main use is for public health research, providing the data that can be used to relate features of the mother and her pregnancy to the health of the child.
The information on death certificates is subject to a number of uncertainties, depending on how well the informant knew the deceased and the circumstances of the death. For example, information on parents, education, and occupation may not be known if the decedent is an elderly person with no surviving relatives. There is often difficulty in the accuracy and consistency with which causes of death are specified. Incorrect diagnoses are common; in the absence of an autopsy, the exact cause of death may not be known. If a number of conditions contribute to the fatal process, underlying causes and immediate causes may be confused. For some conditions such as AIDS or suicide, the cause of death may be misstated deliberately by the local official because of social stigma.
In addition to births and deaths, vital statistics include marriages and divorces, spontaneous fetal deaths, and abortions. Data on marriages and divorces are legal events that require universal reporting, but they are not very interesting from a public health point of view. Reporting of spontaneous fetal deaths is incomplete, especially for those that occur relatively early in a pregnancy; many may be unrecognized. Induced abortions are also probably somewhat underreported. In some states, the name of the woman who had the abortion is not included in the report for reasons of confidentiality.
Because infant mortality is an important public health issue, the NCHS has set up a special computer system that links vital records of infants born during a given year who died before their first birthday. The linkage allows researchers to compare information on the death certificates with that on the birth certificates, providing insight into factors that contribute to infant deaths.
The Census
The data collected through the vital statistics system and other methods must be converted into rates if they are to be useful for many public health purposes. The calculation requires information on the number of people in the population being referred to, the number that serves as the denominator when a vital statistic is used as the numerator. To calculate age-adjusted or age-specific rates, it is necessary to know how many people are in each age group. To determine sex-specific or race-specific rates, one needs to know how many males and females there are and how many blacks, whites, Hispanics, and people of other races in each sex and each age group. This information is collected by the U.S. Census Bureau, part of the Department of Commerce. Without an accurate count of the American population and all its characteristics, the government’s health statistics would not be accurate.
As every schoolchild knows, the U.S. Constitution requires that the population of the United States be counted every ten years to determine each state’s representation in the House of Representatives. Based on that simple mandate, the Census Bureau has developed a national survey that provides data not only on the geographical distribution of the population and its sex, age, and ethnic characteristics, but also on a wide variety of social and economic characteristics, including education, housing, and health insurance status. Furthermore, because the population is always in flux and its circumstances tend to change fairly quickly, the Census Bureau tracks trends in the population between the decennial censuses, using polls and surveys and other sources of data such as birth and death records, immigration and emigration records, and school statistics. Census Bureau data are vital for the operation of the nation’s social, political, economic, and industrial systems, and they are essential for the practice of public health.
Because census data can determine the political composition of the U.S. Congress and the distribution of federal funds to states and communities, various interest groups carefully monitor how the data are collected. An issue that was particularly controversial in preparing for the year 2000 census concerned how a person’s race is determined. The broad categories previously used in the census were white, black, Hispanic, Asian and Pacific Islander, and American Indian and Alaska Native. Individuals identify their own race and ethnic category. The issue has been further complicated by the fact that interracial marriage and parenthood has become increasingly common in the United States, and many of mixed racial parentage wanted an “interracial” category to be included on the year 2000 census. After considerable debate, the Census Bureau decided against such a category, but it allowed individuals to check more than one racial category for themselves.1 This policy affects race-specific health statistics, but the effect is still small. Only 2.4 percent of the population chose to check more than one race in 2000. In 2010, 2.9 percent checked more than one race.2 Among children, the increase in the multiracial population was dramatic between 2000 and 2010, reaching 4.2 million, with the most common combination being black and white.3
An even more politically controversial issue is the chronic problem of how to count every individual person in the United States. The census is mandated by the U.S. Constitution, and the Supreme Court has interpreted the mandate to mean that every person in the country must be enumerated; no statistical corrections are allowed.4 The process for the 2010 census began in March 2010, when a short questionnaire was mailed or delivered to every household. The head of household was asked to complete the form, providing information on all the residents in the household, and return it to the Census Bureau. If the form was not returned, a second questionnaire was mailed. If there was still no response, the household was called or visited by a census worker to collect the information.
Inevitably, people are missed or counted twice. The missing ones are likely to be the poorest and most marginal members of the population—the homeless, illegal immigrants, fugitives from the law. Wealthy people who own more than one home might be counted twice. The Census Bureau estimates that the 2010 census missed about 10 million people and counted about 36,000 people twice.5 Such errors can lead to systematic inaccuracies in health statistics. For example, blacks tend to be undercounted in the census, while black births and deaths are more accurately recorded, meaning that birth and death rates calculated for blacks tend to be higher than their true value would be if correct population numbers were used for the denominator.
Preparations for the 2010 census, according to The New York Times, were a shambles.6 The agency’s director and deputy director resigned in 2006 over the Bush administration’s lack of support for the census, and it took over a year for a new director to be nominated and confirmed.7 There were partisan battles in Congress about how much effort should be made to count racial and ethnic minorities: Republicans tend not to care that inaccurate counts affect congressional representation, because hard-to-count groups, like minorities, immigrants and the poor, tend to vote Democratic.8 And because census numbers determine allocation of hundreds of billions of dollars in federal funds, cities and states whose populations are undercounted tend to suffer.
A major change in the way the 2010 census was conducted was that only the most basic data was collected from everyone, using what used to be called the short form, which asks for name, age, sex, race and ethnicity, and relationship of everyone living in the household. Previous censuses have sought to gain a fuller understanding of population characteristics by using a long form for about one in six addresses, asking questions about education, housing, employment, transportation, language, ancestry, and other issues useful for governments and businesses. In an attempt to make the collection of this detailed information more efficient and more timely, the Census Bureau in 2005 launched a new ongoing survey called the American Community Survey (ACS), which collects the same kind of information previously collected on the long form. The long form will no longer be used in the decennial census. The ACS is sent each year to about 3 million households selected to be representative of the populations of local jurisdictions. The ACS is designed to help communities plan transportation systems, zoning, schools, healthcare facilities, and housing, as well as the need for social services.9
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