Integrated Health Interview Series (IHIS): Providing Free, Integrated NHIS Data over the Internet Miriam L. King, PhD, Minnesota Population Center Brian R. Lee, MPH, PhD, Minnesota Population Center Andrew Ward, MPH, PhD, Kansas Health Institute

Presenter Disclosures Miriam L. King Brian R. Lee Andrew Ward The following personal financial relationships with commercial interests relevant to this presentation existed during the past 12 months: No Relationships to Disclose

NHIS Strengths Large (60-100k) nationally representative survey Covers health status, behaviors, care Consistent core content, periodic special topics Primary source for tracking progress toward public health goals (e.g.,Healthy People) Suitable for studying health disparities Microdata for 1963-present, PUMS available covering 4 million persons

NHIS PUMS rarely used for multi-year analysis Based on sample from PubMed (1978 forward) 70% use 1 year 10 % use 2 years 20% use 3+ years 4 % used data before and after survey redesign in 1997 DESPITE consistency in subject content

NHIS PUMS problems No. files (500+) No. variables (40,000+) Overwhelming documentation (1000’s pages/yr) Subtle changes (coding schemes, variable names and source files, question wording, universes) Sample design changes NCHS forward-looking, not emphasis on consistency (esp. before 1997)

IHIS Solutions Link and reformat files into 1 per year Create 14,000 consistently-coded variables (7000 now public) Create on-line variable-specific documentation Document subtle changes (universe, linked survey text, weights) Impose consistent codes w/out info loss Data extract engine merges files, creates extract w. only years and variables needed

Methods Support from NICHD (in year 7 of 10) Customized programming System driven by machine understandable metadata (e.g., data dictionaries, variable transformation tables, control files) Humans work in Excel and Word files, saved as XML files read by computers Data recoded via Ruby program w. data stored in relational database

Builds upon other MPC data projects Over 50,000 registered users worldwide: US census microdata (1850-2000, IPUMS) American Community Survey (2000 forward) Census samples from 50+ countries (1960s forward) U.S. Current Population Survey (1962 forward) County-level aggregate U.S. census data, 1790-2000 American Time Use Survey (2003 forward)

IHIS goals Document, make public 7000 remaining integrated variables Add on-line tabulator, family pointers, other features Make IHIS better known (1,000 users now; 75% use multiple years’ data) Encourage classroom use

To Learn More IHIS website: www.ihis.us MPC data website: www.ipums.org NHIS website: www.cdc.gov/nchs/nhis.htm Pick up brochures Visit MPC exhibit for demonstration E-mail IHIS@pop.umn.edu