Finding Datasets for Secondary Analysis

The National Center for Health Statistics (NCHS) operates the Research Data Center (RDC) to allow researchers access to restricted-use data. The RDC is responsible for protecting the confidentiality of survey respondents, study subjects, or institutions while providing access to the restricted-use data for statistical purposes. For access to the restricted-use data, researchers must submit a research proposal outlining the need for restricted-use data. The proposal provides a framework for NCHS to identify potential disclosure risks and how the data will be used. The data research results (analysis) will be reviewed by the RDC staff. Upon approval, the researchers can leave with their analysis but the data stays in RDC.

Why do you want to use restricted data instead of using public use data? 

• To answer your main research question
• To control for confounders/examine effect modifiers
• To combine datasets/link in external data (e.g. ACS, researcher compiled state policy information)
• To use as selection criteria for a study
• To access a more detailed version of a variable (See Restricted NCHS Variables page) 
• To make accurate estimates, you may need restricted information about the sampling frame

Below is the summary steps of requesting the RDA data. Please consult Accessing Restricted Data for detailed information. 

• Step 1: Discuss your approval, merge, and fees with your RDC Analyst. Create a public-use/non-NCHS data file and email to your RDC Analyst.

• Step 2: Review the Disclosure Review Manual and disclosure review procedures. Submit the Confidentiality Orientation Certificate and Designated Agent Forms. Link to the Confidentiality and Disclosure information. 

• Step 3:  Your RDC analyst will create your analytic data file once we have received your public-use/non-NCHS file and payment.

• Step 4: Review the rules for your access mode. 

• Step 5: Conduct analysis and submit output for review.

• Step 6: Update proposal for amendment or project extension. 

• Step 7: Send your manuscript to your RDC Analyst for review before submitting for publication. Finally, send your publication for the RDC user publications. 

A researcher can visit the RDC sites or access by the remote system called ANDRE. 

• NCHS RDC
  • Two locations: Hyattsville, MD and Atlanta, GA
  • Secure room with non-networked computers where researchers can work
• Remote Access System (ANDRE)
  • Researchers submit code from their PC to a remote system which authenticates the users, runs the code, checks for disclosure, suppresses necessary output, and returns it to the researcher
• Federal Statistical RDCs
  • Similar set up to the NCHS RDCs and expands our reach to more than a dozen research institutions across the country
• Staff Assisted
  • Staff runs programs for the researcher

If you are planning to use restricted data, you will be benefited from reviewing how other researchers used the similar data for secondary analysis. Check out the RDC User Publications page to quickly view the publications. Here are some examples:

From National Health and Nutrition Examination Survey

• Gaskin DJ, Thorpe RJ, Jr., McGinty EE, et al. Disparities in diabetes: the nexus of race, poverty, and place. American journal of public health 2014;104(11):2147-55.

From National Health Interview Survey

• Chang MH, Molla MT, Truman BI, et al. Differences in healthy life expectancy for the US population by sex, race/ethnicity and geographic region: 2008. Journal of public health 2015, 37(3), 470-9.

From State adn Local Area Integrated Telephone Survey

• Kreider AR, French B, Aysola J, et al. Quality of health insurance coverage and access to care for children in low-income families. Journal of American Medical Association Pediatrics. 2016;170(1):43-51.

From NCHS Data Linkage 

• Nachman KE, Parker JD. Exposures to fine particulate air pollution and respiratory outcomes in adults using two national datasets: a cross-sectional study. Environmental Health. 2012; 11:25-36.

Externa