The National Health and Nutrition Examination Survey (NHANES), a robust dataset accessed by many researchers each year, was suspended on March 16 due to the pandemic.
Researchers have used previous datasets from the NHANES to link environmental exposures with chronic conditions and monitor trends in the American diet. It is the only survey conducted by the National Center for Health Statistics (NCHS) of the CDC to still be paused; others have resumed, or transitioned to phone interviews for data collection, a CDC spokesperson said.
“It is not clear how long this suspension of field operations will last, but it is our hope to resume operations as soon as is feasibly possible and when it is deemed safe for both staff and participants,” said NHANES Acting Director Ryne Paulose-Ram, PhD.
The survey is unique in that it is typically conducted in person, with researchers collecting biologic specimens from participants, measuring height and weight, and performing face-to-face screening interviews.
NHANES teams are typically deployed to 15 randomly selected and nationally representative counties across the country. The decision to suspend data collection was made with the health and well-being of staff and participants in mind, Paulose-Ram said.
It’s anticipated that the disruption in data collection will reduce the overall sample and delay the release of the 2019-2020 data, according to the American Statistical Association in Alexandria, Virginia.
The survey is important because it can be used to track the impact of health policy on things like obesity, said Dana E. King, MD, of West Virginia University in Morgantown, who has used the dataset for research. With the NHANES delayed, it will be more difficult to track these changes throughout the pandemic, he said.
“It is a problem for us as a healthcare community, and researchers will have a delay in their access to data,” King told MedPage Today.
A literature search turned up 3,730 papers that have been published using NHANES data since the survey began in the 1960s. Past surveys have detected elevated mercury levels in families and identified areas of the country where pregnant women were not taking enough folic acid.
The agency is working on a plan to resume fieldwork and has begun editing what data there were for the 2019-2020 survey pre-pandemic so that it can be accessed by the public in an abbreviated form, Paulose-Ram told MedPage Today in an email. “Our goal has been and continues to be to minimize the impact of the suspension and provide the public and the research community with the data that are needed to meet programmatic and policy needs.”
In the meantime, some members of the NHANES team have turned the mobile laboratory trailers they typically use to conduct physical exams into mobile COVID-19 testing sites.
The parent agency, NCHS, is the primary provider of COVID-19 mortality data and also runs several other surveys.
The National Health Interview Survey (NHIS) shifted to telephone interviewing at the beginning of the pandemic and resumed in-person interviews in July for certain areas. Some aspects of the survey overlap with the information provided in the NHANES, such as questions about height and weight or diagnoses of medical conditions. However, the NHIS relies on self-reported answers from household members, so the findings may not be as accurate as assessments performed through the NHANES.
The agency also collects data on ambulatory services through the National Ambulatory Medical Care Survey (NAMCS). This survey began in May after a 3-week delay and has shifted to telephone interviews. Researchers typically collect patient visit-level data in person, but this will not be abstracted at this time, though this arm of the survey might be resumed in the latter half of the year, a CDC spokesperson said.
NCHS is also partnering with the U.S. Census Bureau to collect data on how households are coping with the pandemic, although this year’s census data collection may also paint an incomplete picture of the nation’s population.
“There are other surveys, some by phone only, so we can find out some information,” King said. “But still, the in-person info, the weighing and lung tests and blood pressure readings, are invaluable.”