So, you’re skimming a health-related news article, and you read a sentence that goes something like this:

“The Centers for Disease Control and Prevention estimate that 16 percent of American children are obese.”

Or this: “According to the Centers for Disease Control and Prevention, osteoporosis is on the rise among American women age 60 and over.”

Did you ever wonder where they get statistics like that? Well, this year they’re getting them from Hampton Roads.

The National Health and Nutrition Examination Survey is in the Hampton Roads area this year. The area was randomly chosen as one of 15 areas in the country to participate in the survey.

The survey, abbreviated NHANES, is a major program of the National Center for Health Statistics, which is part of the Centers for Disease Control and Prevention. NHANES is one of the primary sources of vital health statistics used to shape public health policy, design health programs and develop standards used by physicians worldwide.

The health statistics are collected by using a complex process of random sampling, interviews and examinations. First, the country is split into 15 regions, and one area is randomly chosen from each of the 15 regions. Those 15 areas become the places where NHANES will set up house for about two months each.

In each area, 24 segments are randomly chosen, and within each segment, several households – some in Suffolk, this year – are chosen randomly based on the last U.S. census. Field workers then visit each household with handheld computers, interviewing residents about demographics such as gender, age and race of all people in the household.

Once the demographics are entered into the computer, the software will tell the field worker whether anyone in the household has been chosen to participate in the survey. Those chosen have the option to decline, of course, but the accuracy of the data depends upon most of those chosen participating, said Janis Eklund, the study manager for the Hampton Roads area NHANES.

“If you’re chosen, we want you and not your neighbor,” Eklund said. “When someone chooses not to participate, we lose valuable data.”

The survey attempts to replicate the U.S. population by interviewing about 7,000 individuals, Eklund said. In an effort to encourage more people to participate, each participant receives more than $200 – most of it in cash – if they complete all components of the survey.

The first part of the survey, after someone agrees to participate, is an interview in the participant’s home, where they answer basic questions about their health and nutrition habits. After the first part is over, they receive an appointment to visit the mobile exam center, which currently is set up in the parking lot of the Virginia Modeling, Analysis and Simulation Center in Portsmouth, just over the Suffolk city line.

The mobile exam center is composed of four semi- trailers lined up side by side and connected by a walkway down the center. The trailers, which include a reception area, 12 exam and interview rooms, a doctor’s office, three bathrooms, a laboratory and a staff area, take about three weeks to set up so that they meet all local zoning requirements and have adequate plumbing, Eklund said.

“You’d be surprised what we have in four semis,” she said.

When a participant shows up for their interview, he is greeted in the reception area and promptly changes into loose-fitting clothing provided by the survey personnel. The participant also receives an ID wristband with a bar code that will be used to identify him for the remainder of the survey. Participants then move to the first station, which measures lung function in participants ages 6 to 79. Pulmonary function is a focus this year, because national health officials want to obtain a better picture of how asthma is affecting the U.S. population. Certain tests change from year to year as national health priorities change, Eklund said.

At the next station, staffers measure participants’ height and weight. A table with a yardstick also is available for measuring babies.

The third station is only for people who randomly receive morning appointments. Those people were asked to fast, and will drink a glucose drink at this station. Later, their blood sugar will be measured to see how their body responds to the glucose. This station is part of the ongoing health focus on diabetes, Eklund said.

At the fourth station, survey participants are asked to recall everything they have consumed in the last 24 hours, including the item, where they bought it, the brand name, how much they had to eat, and more. To help them recall how much it was, participants are able to look at and touch a variety of measuring cups, bowls, bottles, boxes and even pictures of butter on knives.

Moving to the fifth station, participants then complete a survey of questions on a computer while alone in a private room. Participants complete the survey themselves, because some of the questions, particularly those about sexual, contraceptive and bathroom habits, could be embarrassing, Eklund said.

“We want to get the best possible data instead of (them) thinking someone’s going to be judgmental,” Eklund said.

At the next station, a doctor takes blood pressure and other vital signs, and answers any questions or concerns they might have. While the NHANES survey does not diagnose illnesses, it does provide a report of findings for participants to discuss with their doctors.

Next, participants provide blood and urine samples for a variety of tests, including screening for diseases, cholesterol, nutrient content and more.

Nearing the end of the exams, participants who have been identified as having worked in high-volume areas receive a hearing test. All participants are screened for periodontal disease – a new test this year, Eklund said, because of the recently discovered link between gum disease and heart disease.

The final test, typically done only on older participants, is a bone density screening.

The entire battery of exams takes about 20 minutes for an infant to three hours for an elderly person. The tests and exams, along with the report of findings, have a value of about $4,500, Eklund said.

Within the following week, participants are called to participate in a follow-up interview, which includes questions about buying habits and a second 24-hour food and beverage recall. A person who comes to the exam will receive $125 in cash, as well as a transportation allowance and costs for babysitting, if needed. If they participate in all follow-up interviews, they receive a check in the mail for $85.

In Hampton Roads, the study sampled 458 households. About 380 people were identified to participate, and more than 200 already have been interviewed.

“We’ve had some people say no and refuse us,” Eklund said. “We’re looking to change the mind of some people.”

Most people who go through the exams say they are happy with how they turned out and surprised with how quickly they were done, Eklund said. Participants are even allowed to bring a friend if they would feel more relaxed, she said.

“We try our best to make them feel comfortable.”

Eklund hopes people in Hampton Roads who initially declined will change their minds, especially after they realize the value of the data collected.

“It’s very worthwhile, not only to the U.S., but also to the people who choose to participate,” she said.

The NHANES trailers in Hampton Roads, which have been here since March 16, will stay until May 13, and then travel to Michigan for their next data collection. For more information on NHANES, visit www.cdc.gov/nchs/nhanes.htm.