Linkage of the Longitudinal Administrative Databank (1982-2016) to the Discharge Abstract Database (1997/1998-2016/2017)

This project creates a LAD – DAD linkage key that allows users to link data on acute inpatient hospitalizations from the Discharge Abstract Database (DAD) with data on income and employment from the Longitudinal Administrative Databank (LAD). The resulting analytical files will allow for the study of relationships between income and hospitalizations such as the study of labour market and financial outcomes experienced by individuals and their families following hospitalizations resulting from acute illness and injuries for example.

The LAD – DAD linkage key allows users to link the Longitudinal Administrative Databank (LAD) with the hospital discharge events obtained from the Discharge Abstract Database (DAD) for all provinces and territories (excluding Quebec). LAD records contain information for a 20% longitudinal sample of Canadian tax filers between 1982 and 2016 and can be linked to the DAD hospitalization records for fiscal years 1997/98 through 2016/17 via the linkage key.

The Data

Longitudinal Administrative Databank (LAD)

The LAD is a random, 20% sample of the T1 Family File (T1FF) tax database. Selection for LAD is based on an individual's social insurance number (SIN). There is no age restriction, but people without a SIN can only be included in the family component. Once a person is selected for the LAD, the individual remains in the sample and is picked up each year from the T1FF if he or she appears on the T1 that year. Individuals selected for the LAD are linked across years by a unique non-confidential LAD identification number (LIN__I) generated from the SIN, to create a longitudinal profile of each individual.

The LAD is augmented each year with a sample of new tax filers so that it consists of approximately 20% of tax filers for every year. The 20% sample has increased from 3,227,485 people in 1982 to 5,579,280 in 2016 (an increase of 73%). This increase reflects increases in the Canadian population and increases in the incidence of tax filing as a result of the introduction of the Federal sales tax credit in 1986 and the Goods and Services Tax credit in 1989.

For more information regarding the LAD, please refer to the LAD Data Dictionary available from your RDC analyst.

Discharge Abstract Database (DAD)

The Discharge Abstract Database (DAD) captures administrative, clinical and demographic information on hospital discharges (including in-hospital deaths, sign-outs and transfers) from all provinces and territoriesFootnote 1, except Quebec. Over time, the DAD has also been used to capture data on day surgery procedures, long-term care, rehabilitation and other types of care. Hospitals in Manitoba started submitting their records to DAD from April 1, 2004. Throughout the fiscal years that are covered in the linkage, there were openings, closure and mergers of institutions.

In the DAD, jurisdiction-specific instructions for collection of data elements evolve over time. Collection of each data element may be mandatory, mandatory if applicable, optional or not applicable. Collection requirements can vary by jurisdiction and by data year.

Researchers will find the listings of DAD data elements under the heading "Data Elements" at the DAD Metadata website. Please note that not all DAD data elements are included in the RDC DAD datasets for this linkage project. A list of available DAD variables is contained in user guide for the linked dataset. The documents on the website include information on mandatory versus optional collection status for each data element by jurisdiction, which is key to understanding coverage of data elements in the DAD.

For this record linkage, DAD records that linked to LAD cohort members from fiscal years 1997/98 through 2016/17 were included.

File structure, layout

All variables from the LAD are available for analysis. Please see appropriate data dictionaries, available from your RDC analyst.

The DAD is an event based file, meaning that there will be more than one record for a person who was hospitalized more than once in the same fiscal year. During the linkage process, all DAD records belonging to the same LAD cohort member were identified using their LIN__I. Researchers can then choose to use the DAD file as an event based file (each row of data represents a hospitalization) or a person based file (each row of data represents an individual).

In order to use the file as a person based file, the researcher must transform the data to include all hospital information for one person as one record (one row on the data file).

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