Multimorbidity and Material and Social Deprivation among High Users of In-Hospital Health Care Services (HSUS)

The purpose of this record linkage project was to create a linked dataset that will allow researchers to analyse the socio-demographic, socio-economic, and health characteristics of higher users of the health care system (HSUs) compared to controls drawn from the population of non-high system users (non-HSUs).

A dynamic cohort of complex, high system users (HSUs) was created through a partnership between the Canadian Institute for Health Research and the Canadian Institute for Health Information using the CIHI's internal datasets: (i) Discharge Abstract Database (DAD), (ii) National Ambulatory Care Reporting System (NACRS), and (iii) Ontario Mental Health Reporting System (OMHRS). For the purpose of this record linkage project, a patient index of HSUs and non-HSUs from the DAD, NACRS and OMHRS were provided to Statistics Canada to form the record linkage cohort.

In order to add demographic and economic information to the cohort, the Annual Income Estimates for Census Families and Individuals (T1 Family File or T1FF), the 2006 Census of Population Long-Form (2006 Census 2B), and the 2011 National Household Survey (2011 NHS) were linked to the health care system usage information.

The Data

High System User Cohort and Control Group

CIHR-CIHI's original HSU cohort and control group were created using the DAD, the NACRS and the OMHRS. A patient index provided by CIHI is made up of an HSU cohort, a control group and those neither in the HSU cohort nor the control group. The details pertaining to the complete dynamic cohort of complex, HSUs released by CIHR-CIHI, including its assumptions, methodology and descriptive statistics, are found on CIHR website4.

For this record linkage project, patients had to be captured by the DAD at least once between fiscal years 2011/12 and 2014/15 to be in-scope. This means that there are DAD patients also captured by combinations of the NACRS and the OMHRS.

Discharge Abstract Database (DAD)

The DAD captures administrative, clinical and demographic information on hospital discharges (including deaths, sigh-outs and transfers). For this record linkage, the DAD files for fiscal years from 2011/12 to 2014/15 were included and they were made up of 13,237,758 hospitalization records in total (before applying any exclusion criteria). Correspondingly, there were approximately 7.27 million patients in total.

The data elements collected through the DAD can vary over year and by jurisdiction. Researchers can find documentation of DAD data elements under the heading Data Elements at the DAD Metadata website1, which should be reviewed to better understand the coverage of DAD data elements related to your specific project. Please note that not all DAD data elements are available in the analytical file for this record linkage project. A list of excluded items are noted in the User Guide available from your RDC analyst.

National Ambulatory Care Reporting System

The NACRS contains data for all hospital-based and community-based ambulatory care (e.g., day surgery, outpatient and community-based clinics and emergency departments). Client visit data are collected at time of service in participating facilities from several jurisdictions. For this record linkage, data spanning the fiscal years from 2011/12 to 2014/15 were included.

Researchers will find the listings of NACRS data elements under the heading Data Elements at the NACRS Metadata website2. The documents on the website include "a comparative list of NACRS data elements for all data submission options, along with a brief description of each data element."2 As with the DAD, the status of a data element may vary due to service type and/or jurisdiction. Please note that not all NACRS data elements are available in the analytical file for this record linkage project.  A list of excluded items are noted in the User Guide available from your RDC analyst.

Ontario Mental Health Reporting System

The OMHRS includes information about all individuals receiving adult mental health services in Ontario, as well as some individuals receiving services in youth inpatient beds and selected facilities in other provinces.

Researchers will find the listings of OMHRS data elements under the heading Data elements at the OMHRS Metadata website3.

Annual Income Estimates for Census Families and Individuals

The T1 Family File is derived primarily from income tax returns which are provided to Statistics Canada by Canada Revenue Agency. The T1FF contains information on sources of income and some demographic indicators which are derived from both the tax filers and non-tax filers. More specifically, the T1FF covers all persons who completed a T1 tax return for the year of reference or who received the Canada Child Tax Benefits (CCTB), their non-filing spouses (including wage and salary information from the T4 file), their non-filing children (identified from three sources: the CCTB file, the births files and a historical file) and filing children who reported the same address as their parents. The TIFFs included in this record linkage were for tax filing years from 2006 to 2014. These data can be used to characterize the association between changes in the income estimates for census families and individuals and the usage of health care services by the HSU cohort or control group.

2006 Census of the Population Long-Form

The 2006 Census 2B covered approximately 20% of all private dwellings in Canada in 2006 and the long-form questionnaire included topics such as education, ethnicity, mobility, income and employment. For the purpose of this linkage project, only those respondents who completed the long-form questionnaire were considered. The data from the 2006 Census 2B were included in the linkage to add socio-demographic and geographic information. Note that the 2006 Census of Population (i.e., short-form and long-form) represented 95 to 97% of the population in the provinces and 93 to 94% of the population in the territories.

The 2006 Census 2B data dictionary and references, the questionnaire and the codebooks (with or without frequencies), as well as technical reports are available to RDC researchers. For more information please contact your RDC analyst.

2011 National Household Survey

The 2011 National Household Survey (2011 NHS) was a voluntary survey that included a random sample of approximately 30% of all private dwellings in Canada in 2011. The 2011 NHS included information on education, ethnicity, mobility, income and employment. As with the 2006 Census 2B, the data from the 2011 NHS were included in the linkage to add socio-demographic and geographic information.

The 2011 NHS data dictionary and references, the questionnaire and the codebooks (with or without frequencies), as well as technical reports are available to RDC researchers. For more information please contact your RDC analyst.

File Structure and Layout

The following files were created for researchers:

• Cohort files
  • There are four cohort files separated by fiscal year of discharge from 2011/12 to 2014/15.
  • Each cohort file consists of 30 variables. Among them, there are 12 indicator variables. Each indicator variable corresponds to a subset cohort by fiscal year (&FY) created by CIHR-CIHI: (i) Acute care costs (COST_&FY); (ii) Length of stay (LOS_&FY); (iii) Frequent hospitalizations (DISCH_&FY); and (iv) Frequent emergency room visits (NACRS_&FY) where &FY in (2011, 2012, 2013, 2014).
• Analytical files
  • DAD analytical files
    • There are four analytical files by fiscal year.
    • Each consists of all DAD transactions of the in-scope population listed in the cohort files between 2011/12 and 2014/15.
  • NACRS analytical files
    • There are four analytical files by fiscal year.
    • Each file consists of all NACRS transactions of the in-scope population listed in the cohort files between 2011/12 and 2014/15.
  • OMHRS analytical files
    • There are four analytical files by fiscal year.
    • Each consists of all OMHRS transactions of the in-scope population listed in the cohort files; the OMHRS analytical files included admissions and discharges occurring between 2011/12 and 2014/15.
  • T1FF analytical files
    • There are nine analytical files by taxation year.
    • Each consists of all taxation records of the in-scope population listed in the cohort files.
    • Each file consists of 53 variables selected from the raw T1FF data
  • 2006 Census 2B analytical file
    • Note that all persons living in institutions (e.g., residents of long-term care facilities) were excluded from the 2006 Census 2B analytical file (RDC version).
  • 2011 NHS analytical file
    • Note that the survey excluded persons living in institutional collective dwellings such as hospitals, nursing homes and penitentiaries.

Restrictions

The linked data should not be used to produce official hospitalization discharge statistics. Official counts and rates of hospitalization are available on the CIHI website.

The linked data cannot be used to produce statistics related to institutions and any outputs at the institution level will be restricted as per the vetting rules.

Institution information can be used as a method to generate other information (e.g., the postal code of the institution can be used to determine distance to a care facility) but cannot be used as an outcome of interest.

The production of statistics using a single data source that is part of the linked data set (e.g., production of statistics using only the DAD, NACRS or OMHRS without a T1FF or Census end point) is restricted unless the statistics are being used to provide context to the outputs created using the linked dataset.