Area-level characteristics of substance-related acute toxicity deaths: a descriptive analysis of a national chart review study of coroner and medical examiner data

On this page

• National chart review study of substance-related acute toxicity deaths
• Key findings
• Background
• Definitions included in this report
• Results
• Discussion
• Acknowledgements
• Disclaimer
• Technical notes
• Limitations
• References

National chart review study of substance-related acute toxicity deaths

This report is part of a series from a national chart review study of substance-related acute toxicity deaths (sometimes called "overdose" or "poisoning" deaths). The study uses coroner and medical examiner data from 2016 and 2017. The study aims to better understand:

• the characteristics of the people who died
• the substances involved, and,
• the circumstances of their deaths

Each publication will focus on specific themes or populations.

Key findings

Among people who died in Canada of substance-related acute toxicity in 2016 and 2017, deaths varied by community population sizes and neighbourhood-level indicators of deprivation (residential instability, economic dependency, ethno-cultural composition, and situational vulnerability):

• The highest percentage of deaths was among people who resided in the largest urban communities with 1,500,000 or more residents (Toronto, Montreal, and Vancouver), making up 30% of deaths.
• The highest rate of death was among people who resided in urban communities with 100,000 to 499,999 residents.
• The highest percentage of deaths and rate of deaths were among people who resided in neighbourhoods with the highest levels of residential instability (neighbourhood population changes), and situational vulnerability (housing challenges, lower education, population identifying as Indigenous).
• Across all community sizes and all four dimensions of deprivation, the majority of deaths were:
  • accidental
  • among males
  • among people aged 30 to 59 years old

Background

Substance-related acute toxicity deaths (ATDs) continue to be a serious public health concern in Canada. Recent surveillance data show the number of ATDs have increased, with 30,843 people dying from apparent opioid toxicity alone between January 2016 and March 2022.^{Footnote 1} Some groups are more likely to experience substance-related harms. This may be related to location (such as, urban, suburban, rural), demographics (such as, age, sex, race), and socioeconomic circumstances (such as, income, employment, education). ^{Footnote 2 Footnote 3 Footnote 4 Footnote 5 Footnote 6 Footnote 7 Footnote 8 Footnote 9}

ATDs affect people living in all communities across Canada, including large urban centres, suburban areas, and small and rural communities. Several provincial reports have shown that while most ATDs occur in large urban areas, many also occur in suburban areas outside of large urban centres. ^{Footnote 10 Footnote 11 Footnote 12 Footnote 13 Footnote 14} A report on hospitalizations due to opioid poisonings in Canada found that rates were highest in urban centres with populations between 50,000 and 99,999 people.^{Footnote 15} Other studies have reported recent increases in substance-related harms in more rural areas.^{Footnote 14 Footnote 16}

Studies looking at differences between communities found higher rates of acute toxicity events and deaths in neighbourhoods with higher levels of deprivation.^{Footnote 17 Footnote 18 Footnote 19} Deprivation refers to the “inability for individuals and communities to attain basic resources and services”^{Footnote 10} such as food, housing, work, education, or social connection. Although deaths occurred across all socioeconomic groups in an Ontario study, approximately one-third of people who died of acute toxicity resided in the neighborhoods with the highest level of deprivation.^{Footnote 10} A recent national study found that rates of opioid-related deaths between 2000 and 2017 were highest in areas with the lowest income levels.^{Footnote 19}

While income is one indicator of deprivation, it is important to also consider its combined effects with other indicators such as employment, education, housing, race, and the living environment. Area-level deprivation indices, which combine many of these indicators into one measure, are useful tools in understanding health and social inequalities. Where demographic and socioeconomic information is unavailable at the individual-level, we can use area- or neighbourhood-level information to better understand the circumstances of people who died of acute toxicity.

This report describes the distribution of ATDs in Canada between 2016 and 2017 across rural and urban locations, and by neighbourhood-level indicators of deprivation. Coroner and medical examiner data from the national chart review study of ATDs were linked to the Statistics Canada Postal Code Conversion File Plus (PCCF+)^{Footnote 20} and the Canadian Index of Multiple Deprivation (CIMD).^{Footnote 21} For details on the data sources and their limitations, refer to the technical notes section below. The aim of this analysis was to examine ATDs by i) community sizes and metropolitan influence zones and ii) by area-level deprivation, as measured by the four dimensions of the CIMD: residential instability, economic dependency, ethno-cultural composition, and situational vulnerability.

Definitions included in this report

Acute toxicity death (ATD) (sometimes described as an "overdose" or "poisoning" death):^{Footnote 22} An individual who, according to the death certificate, autopsy report, or coroner or medical examiner report, died after an acute intoxication or toxicity resulting from substance use where one or more of the substances was a drug or alcohol. This includes deaths with an accidental (unintentional), suicide (intentional), or undetermined manner of death.

Community size and metropolitan influence zones (CSizeMIZ):^{Footnote 20} Identifies i) urban areas based on the 2016 census population size in each census metropolitan area (CMA) or census agglomeration (CA); and ii) rural and remote areas outside of CMAs and CAs by metropolitan influence zones (MIZ).

• CMAs consists of a population of at least 100,000 residents
• CAs must have a core population of at least 10,000 residents
• MIZ classify areas outside of CMAs and CAs by the degree of influence (strong, moderate, or weak or no influence) a CMA or CA has on them. A MIZ category is based on the percentage of the population who commute to work in the core of any CMA or CA.

The following CSizeMIZ categories were used in this analysis:

1. CMAs with a population of 1,500,000 residents or more (Toronto, Montreal, and Vancouver).
2. CMAs with a population between 500,000 and 1,499,999 residents.
3. CMAs or CAs with a population between 100,000 and 499,999 residents.
4. CAs with a population between 10,000 and 99,999 residents.
5. Strong MIZ are areas where 30% to 50% of residents commute to work in any CMA.
6. Moderate MIZ are areas where at least 5% but less than 30% of residents commute to work in any CMA or CA.
7. Weak or no MIZ are areas where less than 5% of residents commute to work in any CMA or CA and include territories outside of any CA.

Dissemination area (DA):^{Footnote 20} A geographic unit with a population that typically ranges from 400 to 700 people. DAs are the smallest geographic unit for which all census data is collected.

Deprivation:^{Footnote 10} Refers to the "inability for individuals and communities to attain basic resources and services" such as food, housing, work, education, or social connection.

The Canadian Index of Multiple Deprivation:^{Footnote 21} A geographically-based index developed by Statistics Canada, consisting of four composite dimensions of deprivation (refer to the technical notes section for more information), including:

1. Residential instability: This dimension relates to the changes in neighbourhood populations over time. It combines the proportion of dwellings that are apartment buildings, dwellings that are owned, persons living alone, the population who moved within the past five years, and the population that is married or common-law. Deprivation quintiles (1 – lowest deprivation to 5 – highest deprivation) were used.
2. Economic dependency: This dimension relates to sources of income and labour force participation. This dimension combines the proportion of the population aged 65 and older, the proportion of the population participating in the labour force, the ratio of employment to population, the dependency ratio (population aged 0 to 14 and aged 65 and older divided by population aged 15 to 64), and the proportion of the population receiving government transfer payments. Deprivation quintiles (1 – lowest deprivation to 5 – highest deprivation) were used.
3. Ethno-cultural composition: This dimension combines the concentration of the population who self-identify as a visible minority, who are recent immigrants, who are foreign-born, and who do not have knowledge of either official language (English or French). Concentration quintiles (1 – lowest concentration to 5 – highest concentration) were used.
4. Situational vulnerability: This dimension relates to variations in housing, education, and demographic characteristics and combines the proportion of dwellings needing major repairs, the population that identifies as Indigenous, and the population aged 25 to 64 without a high school diploma. Colonization and historical, political, social, and economic conditions place Indigenous peoples at higher risk of poor health.^{Footnote 23 Footnote 24} Deprivation quintiles (1 – lowest deprivation to 5 – highest deprivation) were used.

Percentage of deaths: The number of deaths in a specific category relative to the total number of deaths in that population. For example, the percentage of the deaths that occurred in residents of communities with 1,500,000 or more residents among all people who died of an acute toxicity event was 30.0%.

Death rate: The number of deaths in a specific population during a specified time, expressed as the number of deaths that occurred per a given population size (for example, (number of deaths/population) x 100,000)). For example, the crude death rate among people who have died of an acute toxicity event in 2016 or 2017 in communities with 1,500,000 or more residents was 10.9 deaths per 100,000 residents. Comparing rates allows us to see whether some populations are more affected than others. Crude rates have no adjustments for other factors, like age, which might affect the death rate. Age-adjusted rates account for differences in death rates that are due to different age distributions in populations by using the 2016 Canadian population as a reference to compare against.

Results

During the study period (between January 1, 2016, and December 31, 2017), at least 9,004 people died from substance-related acute toxicity in Canada (excluding Manitoba). Data for Manitoba were not available at the time of this report.

Acute toxicity deaths by community population size

Over 80% of people who died from an acute toxicity event were residents of urban areas with at least 10,000 residents (Table 1). While the highest percentage of deaths were among residents of communities with 1,500,000 or more residents, age-adjusted death rates were highest in people who lived in communities with a population of 100,000 to 499,999 residents (15.9 per 100,000), followed by communities with 500,000 to 1,499,999 (15.0 per 100,000) and 10,000 to 99,999 residents (14.8 per 100,000) (Figure 1). Rates in rural areas outside of CMAs/CAs ranged from 7.9 per 100,000 in communities that had a strong metropolitan influence to 12.0 per 100,000 in communities with a weak or no metropolitan influence.

Table 1. Percentage of acute toxicity deaths in Canada (excluding Manitoba) in 2016 and 2017 by community size and metropolitan influence zone (MIZ) category

Community size and metropolitan influence zone category (CSizeMIZ)	Percentage of deaths (N=9,044)
1,500,000+ residents	30.0%
500,000 – 1,499,999 residents	20.7%
100,000 – 499,999 residents	21.6%
10,000 – 99,999 residents	11.2%
Strong MIZ	3.2%
Moderate MIZ	4.9%
Weak/no MIZ	3.6%
Missing	4.8%
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Postal Code Conversion File Plus.

Figure 1: Text equivalent

Community size and metropolitan influence zone category (CSizeMIZ)	Age-adjusted death rate (per 100,000 population)
1,500,000+ residents	10.7
500,000 – 1,499,999 residents	15.0
100,000 – 499,999 residents	15.9
10,000 – 99,999 residents	14.8
Strong MIZ	7.9
Moderate MIZ	10.9
Weak/no MIZ	12.0
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Postal Code Conversion File Plus.

By sex and age

Across all community sizes, the majority of ATDs occurred among males (61.2% to 74.3%) and those aged 30 to 59 years old (18.5% to 28.1%) (Table 2). The percentage of ATDs was lowest among people aged 19 years or less (1.7% to 2.7%), followed by those 60 years or more (9.5% to 17.8%) and 20 to 29 year olds (13.1% to 18.3%) across all community size categories.

Table 2. Sex and age distribution of people who died of acute toxicity in Canada (excluding Manitoba) in 2016 and 2017 by community size and metropolitan influence zone (MIZ) category

Community size and metropolitan influence zone category	Sex		Age group (years)
	Female (N=2,653)	Male (N=6,392)	19 or less (N=194)	20 to 29 (N=1,514)	30 to 39 (N=2,202)	40 to 49 (N=1,947)	50 to 59 (N=2,089)	60 or more (N=1,098)
1,500,000+ residents (N=2,712)	25.7%	74.3%	2.2%	15.7%	22.6%	21.4%	24.9%	13.2%
500,000 – 1,499,999 residents (N=1,872)	29.5%	70.5%	2.5%	18.3%	29.1%	19.6%	21.0%	9.5%
100,000 – 499,999 residents (N=1,952)	32.1%	67.9%	2.1%	17.0%	23.7%	21.5%	22.6%	13.1%
10,000 – 99,999 residents (N=1,013)	30.7%	69.3%	1.7%	17.4%	23.0%	22.2%	23.2%	12.5%
Strong MIZ (N=292)	29.1%	70.9%	Suppressed	Suppressed	18.5%	21.2%	28.1%	17.8%
Moderate MIZ (N=442)	37.6%	62.4%	2.7%	13.1%	20.1%	24.0%	23.3%	16.7%
Weak/no MIZ (N=327)	38.2%	61.2%	Suppressed	17.1%	23.9%	20.5%	24.2%	Suppressed
Missing (N=434)	20.5%	79.5%	Suppressed	20.0%	29.3%	27.6%	18.4%	Suppressed
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Postal Code Conversion File Plus. Note: To protect privacy due to small counts, cases with other and unknown sex are grouped with female and cells with counts less than 10 were suppressed.

By manner of death

The majority of ATDs were accidental across all CSizeMIZ categories (Table 3). Suicide was less common and was identified as the manner of death in 14.1% to 24.0% of cases compared to 70.9% to 82.8% of accidental deaths across all community sizes.

Table 3. Percent of people who died of acute toxicity due to manner of death in Canada (excluding British Columbia and Manitoba) in 2016 and 2017, by community size and metropolitan influence zone (MIZ) category

Community size and metropolitan influence zone category (CSizeMIZ)	Manner of death
	Accident (N<5,172)	Suicide (N<1,120)	Undetermined or unknown (N<264)
1,500,000+ residents (N=1,552)	76.1%	18.8%	5.2%
500,000 – 1,499,999 residents (N=1,858)	82.8%	14.1%	3.1%
100,000 – 499,999 residents (N=1,363)	79.2%	17.0%	3.7%
10,000 – 99,999 residents (N=730)	76.4%	19.2%	4.4%
Strong MIZ (N=247)	70.9%	21.5%	7.7%
Moderate MIZ (N=363)	73.0%	24.0%	3.0%
Weak/no MIZ (N=256)	77.0%	18.0%	5.1%
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Postal Code Conversion File Plus. Note: Data for British Columbia was excluded from these analyses as data on ATDs due to suicide was not available for this province. Data for Manitoba was not available at the time of analysis. Data for cases with missing CSizeMIZ categories (N<236) were suppressed due to cell counts less than 10.

Acute toxicity deaths by neighbourhood-level indicators of deprivation

Between 15.2% and 28.9% of deaths were in neighbourhoods ranked as the most deprived (or concentrated) quintiles for each of the four CIMD dimensions (Table 4). As shown in Figure 2, age-adjusted rates of ATDs were the highest in neighbourhoods with the highest levels of residential instability (17.7 per 100,000, compared with 5.7 in the lowest level) and situational vulnerability (18.7 per 100,000, compared with 6.9 in the lowest level). The rates of deaths were also higher in neighbourhoods with the highest level of economic dependency (13.0 per 100,000 compared with 9.0 per 100,000 in the lowest level); however, the differences between quintiles were less pronounced and quintiles 3 and 4 had similar rates (10.4 and 10.3 respectively). For the ethno-cultural composition dimension, death rates peaked in quintile 3 (13.0 per 100,000), and were the lowest in both the least (7.2 per 100,000) and most concentrated (9.3 per 100,000) quintiles.

Table 4. Percentage of acute toxicity deaths in Canada (excluding Manitoba) in 2016 and 2017, by quintile for the dimensions of the Canadian Index of Multiple Deprivation

Dimension	Quintile ranking	Percentage of deaths (N=9,044)
Residential instability	1 - lowest	7.2%
	2	9.1%
	3	12.4%
	4	18.5%
	5 - highest	28.9%
Economic dependency	1 - lowest	17.5%
	2	15.2%
	3	14.7%
	4	13.5%
	5 -highest	15.2%
Ethno-cultural composition	1 - lowest	8.4%
	2	12.9%
	3	18.3%
	4	18.2%
	5 - highest	18.2%
Situational vulnerability	1 - lowest	13.9%
	2	12.5%
	3	12.6%
	4	15.6%
	5 - highest	21.5%
Missing		23.9%
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Postal Code Conversion File Plus. Note: The analysis by CIMD quintiles has a higher percentage of missing data. Please refer to the limitations section for more information.

Note: Quintile rankings: 1 = lowest level of deprivation (or concentration for ethno-cultural composition), 5 = highest level of deprivation (or concentration for ethno-cultural composition).

Figure 2: Text equivalent

Dimension	Quintile ranking	Age-adjusted death rate (per 100,000)
Residential instability	1 - lowest	5.7
	2	6.3
	3	8.3
	4	12.6
	5 - highest	17.7
Economic dependency	1 - lowest	9.0
	2	9.8
	3	10.4
	4	10.3
	5 -highest	13.0
Ethno-cultural composition	1 - lowest	7.2
	2	10.0
	3	13.0
	4	11.5
	5 - highest	9.3
Situational vulnerability	1 - lowest	6.9
	2	8.0
	3	9.0
	4	12.0
	5 - highest	18.7
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Canadian Index of Multiple Deprivation.

By sex and age

A greater percentage of deaths were observed in males and people aged 30 to 59 years across all quintiles for all four dimensions of the CIMD (Table 5). The percentage of ATDs was lowest among people aged 19 years or less (1.2% to 4.9%) and 60 years or more (8.9% to 19.5%) across all quintiles for all four dimensions of the CIMD.

Table 5. Sex and age distribution of people who died of acute toxicity in Canada (excluding Manitoba) in 2016 and 2017 by the four dimensions of the Canadian Index of Multiple Deprivation

Dimension	Quintile ranking	Sex		Age group (years)
		Female (N=2,648)	Male (N=6,392)	19 or less (N=194)	20 to 29 (N=1,514)	30 to 39 (N=2,202)	40 to 49 (N=1,947)	50 to 59 (N=2,089)	60 or more (N=1,098)
Residential instability	1 – lowest (N=655)	33.0%	67.0%	4.9%	18.8%	22.1%	18.9%	23.1%	12.2%
	2 (N=820)	29.9%	70.1%	2.7%	18.2%	25.0%	21.0%	19.4%	13.8%
	3 (N=1122)	29.1%	70.9%	2.3%	18.2%	25.3%	19.7%	21.8%	12.8%
	4 (N=1673)	30.4%	69.7%	2.0%	18.1%	24.8%	21.9%	22.7%	10.5%
	5 - highest (N=2611)	31.9%	68.1%	1.8%	13.5%	22.0%	21.9%	26.0%	14.8%
Economic dependency	1 - lowest (N=1,583)	27.4%	72.7%	2.7%	19.3%	27.8%	20.5%	20.8%	8.9%
	2 (N=1,374)	30.3%	69.7%	2.6%	17.0%	27.2%	20.6%	20.8%	11.8%
	3 (N=1,333)	30.8%	69.2%	2.4%	17.6%	24.4%	20.0%	23.5%	12.1%
	4 (N=1,218)	32.9%	67.2%	2.7%	15.9%	19.6%	22.1%	26.0%	13.7%
	5 - highest (N=1,373)	34.2%	65.8%	1.2%	11.9%	17.9%	22.7%	26.7%	19.5%
Ethno-cultural	1 - lowest (N=763)	35.8%	64.2%	1.7%	13.0%	17.6%	23.7%	26.0%	18.1%
	2 (N=1,170)	34.7%	65.3%	2.1%	16.4%	20.2%	21.1%	24.8%	15.4%
	3 (N= 1,653)	30.6%	69.4%	2.2%	16.3%	26.1%	21.1%	23.1%	11.2%
	4 (N=1,648)	29.5%	70.5%	2.9%	17.4%	24.6%	20.8%	22.2%	12.0%
	5- highest (N=1,647)	27.8%	72.3%	2.3%	17.2%	25.3%	20.3%	22.9%	12.0%
Situational vulnerability	1 - lowest (N=1,260)	27.9%	72.1%	2.8%	21.1%	24.9%	19.8%	19.3%	12.1%
	2 (N=1,127)	30.2%	69.8%	2.8%	18.3%	24.3%	19.7%	21.3%	13.7%
	3 (N=1,139)	29.9%	70.2%	2.6%	16.9%	24.8%	19.3%	22.9%	13.5%
	4 (N=1,413)	31.9%	68.1%	1.8%	14.3%	24.4%	22.4%	24.6%	12.5%
	5 - highest (N=1,942)	33.2%	66.8%	2.1%	13.6%	21.1%	23.1%	26.8%	13.4%
Missing	(N=2,163)	24.2%	75.8%	1.5%	17.8%	26.7%	22.8%	22.1%	9.2%
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Canadian Index of Multiple Deprivation. Note: To protect privacy due to small counts, cases with other and unknown sex are grouped with female. A higher percentage of deaths is observed among people aged 60 years or more who live in neighbourhoods with the highest level of economic dependency (19.5%). However, this may be explained by one of the indicators of economic dependency being the dependency ratio (population aged 0 to 14 and aged 65 and older divided by population aged 15 to 64).

By manner of death

Most ATDs were accidental and suicide was less common for all quintile rankings of each dimension (Table 6). Accidental deaths occurred between 2.6 and 5.6 times more than suicide across all quintiles for all four dimensions of the CIMD.

Table 6. People who died of acute toxicity in Canada (excluding British Columbia and Manitoba) in 2016 and 2017 by manner of death and the four dimensions of the Canadian Index of Multiple Deprivation

Dimension	Quintile ranking	Manner of death
		Accident (N<5,172)	Suicide (N<1,120)	Undetermined or unknown (N<282)
Residential instability	1 - lowest (N=566)	76.9%	20.3%	2.8%
	2 (N=673)	75.0%	21.3%	3.7%
	3 (N=848)	77.6%	17.8%	4.6%
	4 (N=1,381)	80.6%	15.4%	4.0%
	5 - highest (N=2,078)	79.4%	16.0%	4.7%
Economic dependency	1 - lowest (N=1,330)	82.2%	14.8%	3.0%
	2 (N=1,116)	79.3%	15.7%	5.0%
	3 (N=1,043)	78.1%	17.8%	4.0%
	4 (N=968)	75.8%	19.3%	4.9%
	5- highest (N=1,089)	76.5%	19.2%	4.3%
Ethno-cultural composition	1 - lowest (N=670)	68.4%	26.3%	5.4%
	2 (N=916)	76.3%	19.9%	3.8%
	3 (N=1,219)	80.5%	16.2%	3.4%
	4 (N=1,350)	80.2%	14.7%	5.1%
	5 - highest (N=1,391)	81.9%	14.5%	3.7%
Situational vulnerability	1 - lowest (N=1,034)	77.8%	18.9%	3.4%
	2 (N=901)	78.0%	18.4%	3.6%
	3 (N=869)	74.5%	21.2%	4.4%
	4 (N=1,154)	78.3%	16.3%	5.4%
	5 - highest (N=1,588)	82.0%	13.9%	4.1%
Data source: Data as of September 2022 from a national chart review study of substance-related acute toxicity deaths in 2016 and 2017, Public Health Agency of Canada. Statistics Canada's Canadian Index of Multiple Deprivation. Note: Data for cases with missing neighbourhood-level deprivation data (N<1,010) were suppressed due to cell counts less than 10.

Discussion

This report presents new data to describe ATDs that occurred between 2016 and 2017 by community population size and neighbourhood-level deprivation measures. While ATDs affect communities across Canada, the majority of deaths were observed among urban communities and neighbourhoods with higher levels of some deprivation indicators, with differences observed across sexes, age groups, and manners of death.

Previous reports have shown that most ATDs have occurred in larger urban centres, but recently death rates have risen in mid-sized urban communities and rural areas. ^{Footnote 10 Footnote 11 Footnote 12 Footnote 13 Footnote 14 Footnote 16} The data presented in this report show how communities of all sizes have been affected by ATDs. Although mortality rates among residents of rural communities (outside of CMA/CAs with weak, or no metropolitan influence) were higher compared to the largest urban communities (populations over 1,500,000 residents), the highest mortality rates were observed among people who resided in CMA/CAs with populations between 100,000 to 499,999 residents.

Higher mortality rates were also observed in neighbourhoods with higher levels of residential instability, situational vulnerability, and economic dependency. These results are in line with previous studies that have found relationships between indicators of deprivation, such as unemployment, lower income and education, and higher rates of acute toxicity hospitalizations and deaths. ^{Footnote 9 Footnote 19 Footnote 25 Footnote 26} The distribution for the ethno-cultural composition appeared to differ from the other three dimensions, as the highest rates were observed in neighbourhoods with moderate ethno-cultural composition. Prior research has found that opioid poisoning hospitalization rates are lower among visible minority groups (excluding Indigenous populations),^{Footnote 9} but there is limited information available beyond this to understand ethno-cultural factors and ATDs in Canada.

Despite differences in the distribution of deaths, ATDs are not limited to any specific community or location. However, our findings contribute to a better understanding of how some communities may be disproportionately affected. In this report, the integration of several data sources allowed for a closer look at the socioeconomic circumstances and context of people who died of an acute toxicity event in 2016 and 2017. Understanding the context surrounding deaths, including what neighbourhoods may be at disproportionate risk, can help inform public health actions to reduce ATDs across Canada.

Acknowledgements

We would like to acknowledge our collaborators at the offices of chief coroners and chief medical examiners across Canada for providing access to their death investigation files, and the co-investigator team (Brandi Abele, Erin Rees, Matthew Bowes, Songul Bozat-Emre, Jessica Halverson, Dirk Huyer, Beth Jackson, Graham Jones, Fiona Kouyoumdjian, Jennifer Leason, Regan Murray, Jenny Rotondo, Emily Schleihauf, and Amanda VanSteelandt) for their contributions to developing the national chart review study on drug and alcohol-related drug toxicity deaths. We would also like to thank Fiona Koyoumdiian, Brandi Abele, Emily Schleihauf, Colin Steenmsa and Sai Yi Pan for major contributions to this report and the many reviewers for their feedback on earlier versions of this report.

Disclaimer

This report is based on data and information compiled and provided by the offices of chief coroners and chief medical examiners across Canada, and Statistics Canada. However, the analyses, conclusions, opinions, and statements expressed herein are those of the authors, and not necessarily those of the data providers.

Technical notes

Methodology

This report examined area-level characteristics of substance-related ATDs in Canada using information from our national chart review study of coroner and medical examiner data, the PCCF+,^{Footnote 20} and the CIMD.^{Footnote 21} This report is the second in a series of brief reports from the chart review study of ATDs. A more detailed description of this study can be found in the first brief report from this publication series.^{Footnote 22}

The national chart review study of coroner and medical examiner data was conducted to describe and compare the characteristics of all substance-related ATDs that occurred across Canada between 2016 and 2017. Its population of interest includes all individuals who died in Canada between January 1, 2016 and December 31, 2017 from an acute toxicity event resulting from the direct effects of the administration of exogenous substances where one or more of the substances was a drug or alcohol. Variables collected include socio-demographic factors, drug and medical history, antecedent factors, and toxicology findings. This report includes data available as of September 2022 from nine provinces and three territories. Future reports will include data from all provinces and territories.

The CSizeMIZ variable derived from the PCCF+ was used to examine deaths by urban and rural communities. Measures of residential instability, economic dependency, ethno-cultural composition, and situational vulnerability were derived from the CIMD to measure neighbourhood-level deprivation. Cases where the postal code of residence was missing, unknown, or corresponded to a non-residential address (for example, a commercial area, correctional facility, or health care facility) were excluded from this analysis. This includes cases where a person was experiencing homelessness and cases where the postal code was not documented in the case file. However, for cases where the postal code was not available but the municipality of usual residence was, municipality data was manually matched to CSizeMIZ categories.

The percentage of cases by each CSizeMIZ category and by each quintile ranking of the four CIMD dimensions was calculated. Crude and age-adjusted death rates were calculated using direct standardization based on DA-level population estimates from the 2016 Census. Age-adjusted rates were calculated using the following age groups: 19 years or less, 20 to 29 years, 30 to 39 years, 40 to 49 years, 50 to 59 years and 60 years or more. Data were disaggregated by sex, age and manner of death for a more in-depth understanding of the populations assigned to each category. Other or unknown sex had cell counts less than 10 and were grouped with female to protect privacy.

Other data sources

Statistics Canada's Postal Code Conversion File Plus

The PCCF is a Statistics Canada dataset that links Canada Post six-character postal codes with standard geographic areas for which census data are produced.^{Footnote 20} The PCCF+ consists of a SAS program and set of associated datasets derived from the PCCF, including a postal code population weight file, geographic attribute file, health region boundary files, and other supplementary data. The PCCF+ program assigns standard geographic areas based on postal codes and uses population-weighted random allocation for postal codes that link to more than one geographic area. For this study, the PCCF+ was used to obtain DAs and CSizeMIZ categories using each case's 6 character postal code associated with their usual place of residence.

Statistics Canada's Canadian Index of Multiple Deprivation

The CIMD is a well-established, geographically-based index of social inequalities.^{Footnote 21} Developed by Statistics Canada, this index was created using the 2016 Census population to derive indicators of marginalization and deprivation at the DA-level. Previous theoretical frameworks on deprivation, marginalization and factor analysis were utilized to develop its four dimensions, described above, based on area-level census indicators, including residential instability, economic dependency, ethno-cultural composition, and situational vulnerability. Factor analysis is a statistical method that reduces a large number of correlated variables into a fewer number of factors by grouping these factors into distinct themes. Each dimension covers a comprehensive range of indicators, providing multi-faceted data to examine different aspects of deprivation. The CIMD was linked to the PCCF+ and the national chart review study dataset using DA identification codes.

For each of the four dimensions, the CIMD dataset includes both factor scores and a ranked quintile variable, which had been created for the CIMD by ranking factor scores from lowest to highest and dividing them into five equally sized quintiles. The CIMD assigned each DA to one of five quintile ranking categories, with category one corresponding to areas that were the least deprived for a given dimension and category five corresponding to the areas that were the most deprived. In this report, the quintile rankings are used to examine the relationship between ATDs and area-level indicators of deprivation.

Limitations

There were several limitations to the information that could be accessed and included in the national chart review study. Data from Manitoba were not included in this report as they were not yet available as of September 2022, but will be included in the final chart review study dataset. There were higher proportions of missing postal code data from British Columbia and Quebec due to data collection limitations.

Cases where postal code of residence was not reported or was unknown could not be linked with PCCF+ and CIMD data. Postal codes that corresponded to non-residential addresses (for example, commercial or business addresses, hospitals, or correctional facilities) were also excluded from the data linkages. This means that people who were experiencing homelessness and those residing in institutions such as correctional and long-term care facilities were more likely to have been excluded from this analysis. To address this limitation, we examined the municipality of usual residence variable for cases with missing postal code information and manually matched municipality to CSizeMIZ categories. However, we were unable to manually match municipality to smaller levels of geography and since the CIMD is linked by dissemination area (a smaller level of geography than municipality), we were unable to match municipalities to CIMD quintiles. Thus, the analysis conducted on CSizeMIZ categories excludes about 5% of cases, while the CIMD quintile analysis excludes 24% of cases (Figure 3).

1. Cases from the national chart review of corner and medical examiner data of all substance-related acute toxicity deaths that occurred in Canada (excluding Manitoba) between January 1, 2016 and December 31, 2017.
2. Postal codes contained entry errors or corresponded to non-residential areas and could not be linked to the Postal Code Conversion File Plus (PCCF+).

Figure 3: Text equivalent

There are 9,004 cases included in the national chart review of corner and medical examiner data of all substance-related acute toxicity deaths that occurred in Canada (excluding Manitoba) between January 1, 2016 and December 31, 2017. There are 6,985 cases in CME dataset after missing postal code for usual place of residence (2019 cases with cases with missing postal code for usual place of residence). In addition to the 2019 cases with missing postal codes, there were 89 postal codes that we could not match to DA and CSizeMIZ using the PCCF+ because they contained entry errors or corresponded to non-residential areas. Therefore, a total of 6,896 cases were included in analysis by neighbourhood-level indicators of deprivation. The municipality of usual residence variable was examined for the 2,108 cases with either missing postal code (N=2,019) or that could not be linked to the PCCF+ (N=89). Of the 2,108 cases that could not be included in the data linkage, 426 cases did not contain any information on municipality of usual residence (the response for home municipality was missing). The remaining 1,682 cases that did contain a response for home municipality were matched wherever possible to CSizeMIZ categories. 8,570 cases were included in analysis by community population size (1,674 cases were successfully matched to CSizeMIZ categories)

Area-based measures derived at the level of the DA are subject to certain biases. Specifically, observations apply to the area-level and not to every individual within the DA. Further, the PCCF contains multiple records for a postal code when the postal code straddles more than one geographic area. To mitigate this limitation, the PCCF+ probabilistically assigns each postal code record using census derived population weights. This population weighting technique allows a dataset to be matched to census geography in a way that is consistent with the distribution of the overall population.

Additionally, there is a limitation in measuring and reporting on rates of ATDs in Indigenous populations in this report. This is because the 'proportion of the population that identifies as Indigenous' is one out of many indicators used to measure the situational vulnerability dimension of the CIMD and therefore rates for Indigenous peoples may be obscured in the findings.

As this report is descriptive in nature, we did not examine whether the relationship between ATDs and community size or deprivation indices were statistically significant or meaningful. We also did not investigate whether the relationships observed between ATDs and community size or deprivation indices are being influenced by other variables. Future statistical analyses may address this gap.