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Don’t be taken aback if this month someone knocks on your door and asks you how you’re feeling.
The city has been randomly selected by the Centers for Disease Control’s National Center for Health Statistics to participate in its annual study charting the health of Americans across the country.
About 5,000 people nationwide will be selected at random to participate in this year’s National Health and Nutrition Examination Survey. That will include 625 individuals from 24 neighborhoods in the city, according to the acting director of the Philadelphia office, Gessi Rincon.
Last Friday, interviewers began canvassing neighborhoods in South Philly, knocking on doors and asking people to participate. The process is expected to continue through April 25.
The CDC began sampling the health of the country through the NHNES in 1960. In 1999, the agency started conducting the survey annually, selecting 15 counties around the country at random from where to draw a nationally representative pool of participants.
"The whole process has been set up to guarantee randomness of the way we are selecting people," Rincon said. "That way, we get a statistically accurate picture of the community."
Each participant in the survey represents approximately 7,000 other Americans with similar demographics.
The results paint a picture of the nation’s health by determining the prevalence of various diseases and helping researchers determine risk factors for diseases.
Past surveys have provided data to create growth charts used around the country by pediatricians, according to the CDC. The NHANES also has led to policy changes and federal legislation. For example, when the results of 1970s blood studies showed a significant portion of the population had elevated levels of lead in its blood, the government passed regulations eliminating lead from gasoline and solder from food and soft-drink cans. Lead levels have dropped 70 percent in the last 30 years.
The study is conducted in two phases. The public participates in the data-collection phase by responding to an interviewer’s questions.
When a resident answers the door, the interviewer briefly explains the survey and shows his government identification badge, Rincon said. Each worker also carries copies of letters from local health officials endorsing the program. In addition, the CDC notifies police and fire departments of its presence in the community.
The initial questions of the survey are asked from the front doorstep of the home and take about five minutes. First, the interviewer must establish whether the person he is talking to is the head of the household or another resident.
The worker then asks about family size, ages, race, ethnicity and general health questions. After this data is entered into a handheld computer, Rincon said, the computer indicates if the person or any members of his or her family have been selected to participate.
"Based on that information, the computer runs an algorithm which will randomly select people to see if they fall into the sample," Rincon said.
Any further participation is voluntary for those selected, he said, but individuals who choose to complete the entire study will receive compensation — as much as $100 for adults, plus money for a babysitter, if required, and transportation.
"We understand that everyone has a busy life and we try to make it as easy as possible for people to help us out," Rincon said.
If the resident agrees, he will be asked to complete an extensive survey detailing his health history that includes questions about lifestyle, heredity, existing diseases and medical conditions, and diet. This portion will take 45 minutes to an hour.
Then the participant will schedule an appointment at the CDC’s temporary medical center set up at 1324 Arch St. sometime before June 11 to undergo a three-hour battery of tests. All examinations are non-invasive, Rincon said. The tests administered to each individual will vary, he said, but could include any of the following: general physical, blood-pressure test, dental exam, bone scan, vision and hearing tests, and a meeting with a nutritionist.
The study is completely anonymous and individual results are kept confidential by law, Rincon said. When data is compiled, a number, rather than the person’s name, will identify the results.
However, the interviewer will ask participants for their name and address so results can be mailed to them and incorporated with their existing medical files. This is a bonus of the program, Rincon said.
"Not only do we give people compensation for the time they have given us," he said, "they also get the results of a fairly comprehensive medical picture of themselves that if they tried to do on their own … would cost them quite a bit."
