Injury and Poisoning Estimates from the National Health Interview Survey -Why They Differ from Other Estimates Manon Boudreault MPH, Margaret Warner PhD, and Lois Fingerhut, MA National Center for Health Statistics U.S. DEPARTMENT OF HEALTH AND HUMAN SERVICES Centers for Disease Control and Prevention Office of Analysis and Epidemiology 2005 National Injury and Prevention and Control Conference, Denver, CO

Overview National Health Interview Survey -Questionnaire History -Current data Other Injury Data from NCHS -Comparison of data sources Linking NHIS files and public-use data files

medically-attended All medically-attended injuries occurring to any family member during the 3 month period prior to the interview are asked about from an adult family member. civilian non-institutionalized Uses a multistage sample designed to represent the U.S. civilian non-institutionalized population info on over 90,000 persons ) Collected throughout the year, nearly 40,000 households are visited ( info on over 90,000 persons ) NHIS

NHIS Strengths More detailed information : circumstances, cause, and location of episode (64% of the adult episodes are self-reported) Nearly complete external cause codes Largest range of data available in one system Linkable with other national data sets

Data prior to the redesigned 1997 NHIS Placement, phrasing and number of questions Recall period Severity threshold Prior years are not directly comparable due to: 25% injuries due to these and other changes (1995 to 1997)

Analysis of Recall Bias Questionnaire recall period … past 2 weeks ? (before 1997) to… past 3 months ? (current ) More severe injuries (fractures and sprains/strains) showed similar numbers whether recall was 2 weeks or 3 months. Further analyses showed drop in reporting minor injuries after 5 weeks. “Recall Bias” Fewer minor injuries reported

Annual estimates (NHIS) of injury and poisoning episodes Episodes in millions Year Same questions Nearly same questions Detailed questionnaire history:

“Packed” question : DURING THE PAST THREE MONTHS, that is since {91 days before today date}, {were/was} {you/anyone in the family} injured or poisoned seriously enough that {you/they} got medical advice or treatment? Three questions in one: 1)Were you injured? 2)Were you poisoned? 3)Did you seek medical advice?

“Unpacked” question- NHIS 2004 During the past three months, that is since {January 2}, did you have an injury where any part of your body was hurt, for example, with a broken bone, sprain, burn, wound, bruise, or animal or insect bite? During the past three months, that is since {January 2}, were you poisoned by swallowing or breathing in a harmful substance such as bleach, carbon monoxide, or too many pills or drugs? Did you talk to or see a medical professional about this {injury/poisoning}?

Annual estimates (NHIS) of injury and poisoning episodes Episodes in millions Year * Same questions Nearly same questions New questions * *Preliminary data, anticipated substantial increase based on revised questions.

Comparison of Other NCHS Data Sources with the NHIS

Important Factors Related to NHIS Estimates Recall period effects reporting of minor injuries Proxy reporting for all children and 36% of adult i/p episodes Relatively few intentional injuries reported Total treatment may not be reported Institutionalized population not captured, e.g., nursing homes Acute injury episodes rather than chronic injury

Age in years InstitutionCommunity Number of visits per 100 persons Annual rate of injury-related ED visits for seniors by patient residence: From the NCHS 2004 Data Users Conference Presentation Overview of the NAMCS and NHAMCS by Linda McCaig and David Woodwell Institution is defined as a nursing home or other institution, such as a prison, mental hospital, group home for the mentally or physically disabled. Source: NCHS, NHAMCS-ED

Injury poisoning episodes (all), pain/swelling* due to injury (adults), and some disability due to injury (adults): In millions Injury/poisoning episodes-all ages-(I/p file) Adults- *pain/ache/stiffness/swelling due to injury-(sample adult file) Adults w/some disability due to injury-(sample adult file) i/p episodes disability pain

Some disability due to injury: Number of adults in millions *Selected from a printed condition list as “fracture/bone/joint injury” and/ or “other injury” (sample adult section/file) Injury condition duration:

NCHS Injury Data Sources Medical/Administrative Records Household Interview

Household Interview NHIS episodes (2002) 23.7 million episodesNHIS Treatment reported (2002) Medical Records-2002 EstimatesNHIS NHAMCS ED visits 33.0 million13.1 million NHAMCS OPD visits 10.2 million3.0 million NAMCS Dr. visits 99.2 million8.2 million NHDS- discharges 1.8 million1.0 million Injury-related treatment: NHIS/other NCHS surveys

Treatment reported in the NHIS All treatment received most likely not reported—only 16 percent of those hospitalized with a fracture also reported a visit to a doctor. Compared with other NCHS treatment administrative databases, differences in frequency were greatest for physician-based office visits. Fracture ED visits and reported fracture NHIS ED visits were the most similar (1.4 times the NHAMCS-ED).

Medical Records-Based Data More accurate accounting of total treatment / healthcare utilization Treatment, procedures, and prescribed drug information available Collection limited to what’s entered on form/medical chart Automated collection systems may differ (NHDS) Injury mechanism/cause often unspecified Strengths Limitations

NHIS episodes2.6% NHAMCS ED visits 26% NHAMCS OPD visits 49% NAMCS Dr. visits 45% NHDS- discharges 36% Percent with unspecified cause of injury: 2002

NHIS Public-Use Files and Linking

NHIS-Public Use Data Files For estimated annual injury and poisoning episodes: - Person file -Injury and poisoning episode file -Injury verbatim file Using SAS, STATA, SPSS

NHIS Links Expand Scope of Available Injury Data More within NHIS -Sample adult -Sample child External links to NHIS -Medical Expenditure Panel Survey (MEPS)/NHIS linkage -National Death Index (NDI)/NHIS linkage

NHIS Injury/Poisoning Episodes linked with NHIS Sample Adult File Sample Adult Questionnaire -Cigarette smoking - physical activity -alcohol consumption - height and weight -gender specific questions -specific and chronic conditions -respiratory ailments -sensory impairment -mental health -health care access and utilization

NHIS Links with Other National Data Sets MEPS/NHIS Link NHIS/1996 MEPS to 2002 MEPS/2001 and 2000 NHIS links -Health services used, cost of services, and how paid. NDI/NHIS Link linked file includes NHIS survey years with mortality follow-up through Age at NHIS interview, -underlying and multiple cause of death -Other variables by special request (e.g., occupation)

National Health Interview Survey Much more detailed info on cause /circumstances Provides national estimates collected from persons not records Largest range of data available in one system Responses to specific prevention questions Linking to other major data systems Proxy reporting Recall bias Intentional injuries masked or underreported Missing institutionalized population (e.g., nursing homes) StrengthsLimitations

Questions or additional information NHIS: Injury Data and Resources Website!