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Cause of injury or poisoning, first response

Codes and Frequencies

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For all injury/poisoning episodes that occurred in the past 3 months, IRCAUS1 reports the first interpreted cause of the injury or poisoning. For each unique episode, the interviewer selected the category for IRCAUS1 based on what she/he felt best described the respondent's description of how the injury or poisoning happened. Please see the Comparability Tab for information on poisoning episodes. The second cause of injury, where provided, is available in the variable IRCAUS2.

IRCAUS1 is an injury-level variable.

IRCAUS1 is part of a series of variables initiated in 1997 that systematically report persons' injuries and poisonings, the cause, what the person was doing while sustaining the injury or poisoning, and where she/he was at the time of the injury or poisoning. For related variables and additional information, please see the User Note on Injuries and Poisonings or use the IPUMS NHIS search function and drop-down menus.


IRCAUS1 is only asked about injuries, and the original data does not include poisoning episodes. However, persons could report a poisoning as the cause of their injury episode. To improve comparability with other cause of injury variables over time, IPUMS reclassifies the "out of universe" poisoning episodes to be in universe and have the cause of "Poisoning". This offers more complete information on all episode-level data; however, the assignment of these episodes to the "poisoning" category was done by IPUMS staff based on original data source, not by the interviewer as with other categories for IRCAUS1.. Persons can report a cause of their poisoning episode; this information is available in IRPOISON; this does not include injury episodes. Users may use IRPOISON to differentiate between injury episodes where a person reported "Poisoning" as the cause, and poisoning episodes that have been assigned to the "Poisoning" category by IPUMS staff.

IRCAUS1 is similar to, but not necessarily compatible with IRCAUSE. IRCAUSE was offered in earlier years and has slightly different categories. NCHS documentation notes that these variables may not be comparable. Value labels are similar for the 2004-2016 and 2017 categories "Fall," and "Fire, burn, scald." The 2017 categories specify that a person is a driver or passenger "in a motor vehicle" and "of other mode of transportation (boat, plane, train, golf cart, etc."; while the 2004-2016 version specifies only that the person is "[i]n a motor vehicle" or "[i]n a boat, train, or plane". Users should note there are differences in the phrasing for the 2017 categories "Rider of a bicycle/tricycle/unicycle," and "Pedestrian walking or on skateboard, skates, skis, etc. struck by vehicle or bike" as compared to the earlier versions: "On a bike, scooter, skateboard, skates, skis, horse, etc." and "Pedestrian who was struck by a vehicle such as a car or bicycle". Additionally, persons can report a poisoning as the cause of their injury in 2017, and several response categories similar to those available in 1997-2003 are included again in 2017. Users are encouraged to review IPUMS and NCHS documentation before combining these variables.


  • 2017: All injuries and poisioning episodes.


  • 2017