A preprint of our work on multiple-cause mortality is now available.

Peters, P. A.; Klym, M.; Lopez Barrios, M.; McGaughey, T. Cause-Related Mortality in Canada by Income Quintile: Examining the Impact of Multiple Causes before and after the COVID-19 Pandemic. Preprints 2024, 2024092342.

Abstract

Mortality rates are fundamental to understanding the overall health of a population. However, statistics are usually reported using the primary underlying cause of death, overlooking potentially relevant contributing causes listed on death certificates. This paper presents indicators for multiple cause-related mortality in Canada from 2000 – 2022. Deaths from the Canadian Vital Statistics Database (2000 – 2022) were merged with multiple cause files and classified into 136 cause of death groupings. Summary statistics for multiple causes were calculated, including the Standardized Ratio of Multiple to Underlying (SRMU), which is also calculated by neighbourhood income quintile. Age-Standardized Mortality Rates (ASMR) were calculated for the underlying cause of death (ASMRUC) and compared to rates including any mention of each respective cause (ASMRAM). These were then compared to ASMRs based on a contributing-cause weighting scheme (ASMRW). The average number of causes reported on death certificates has increased from 2.79 in 2002 to 3.19 in 2021. Those in the lowest income quintiles have a higher average number of causes (3.31 in 2021) compared to those in the highest income quintile (3.09 in 2021). When employing multiple cause weighting strategies, the rank order of age-standardized mortality rates is significantly elevated for conditions including renal failure, hypertension, pneumonia, septicemia, arterial fibrillation, and artery diseases. Multiple cause-of-death approaches provide further insight into the patterns of mortality and highlight conditions that become leading causes using weighted approaches. This provides evidence to support efforts to address these conditions. There are also differences in multiple causes of death reporting by income quintile which warrants further investigation.

Keywords

multiple causes of death; comorbidity; mortality; mortality determinants; COVID-19; chronic diseases; population health; demography

The post Preprint: Cause-Related Mortality in Canada by Income Quintile appeared first on Determinants.

Poster Images

COVID-19 Deaths in Canada

Authors: Michel Lopez Barrios, Tomoko McGaughey, Morgan Klym, and Paul Peters

Presented at: Population Association of America Conference, April 13, 2023.

The analysis of COVID-19 mortality using a single cause represents a significant limitation to understanding the disease. In this study, the relationship between the underlying cause of COVID-19 with its comorbidities provides important inputs for future comparisons.

COVID-19 has driven higher mortality since March 2020, resulting in an increasingly large cumulative increase of deaths. Since October 2021, COVID-19 as a contributing factor to excess deaths has decreased. In the first year of the pandemic, COVID-19 was coded largely as the underlying cause (UC) of death. After the 1st year, COVID-19 was increasingly coded as a contributing cause (CC) of death.

COVID-19 and Contributing Causes

We compared COVID-19 deaths from 2020 (Alpha) to 2021 (Beta, Delta & Gamma variants). For deaths where the UC was COVID-19, the mean number of CCs increased between 2020 and 2021. The increase in mean number of CCs was seen across the age groups and for both sexes.

Explanations may include:

• A shift in who died from COVID-19
• A shift in coding practices
• Differing impact of COVID-19 strains over the pandemic

Next steps include examining deaths linked to hospital discharge abstracts to better ascertain reasons for the increase.

COVID-19 and Coding Mortality

The Standardized Ratio of Multiple to Underlying Causes is the age-standardised rate for any mention compared to the age-standardised rate when the cause is the UC.

• <2 indicates the cause more often a UC
• 2 indicates equal representation as UC & CC
• 2 indicates the cause is more often a CC

Marginal Change

We used Poisson regression to estimate the marginal change in the average number of CCs for each group of UCs

• The mean number of CCs was higher for all causes in 2021 (3.33), possibly because of excess of mortality in 2020 (3.26).
• Females had a lower mean number of CC (3.25) than males (3.34)
• COVID-19 has a lower mean number of contributing causes (3.48) compared to other infectious diseases (3.50)
• The mean contributing causes of death when COVID-19 was a UC increased from 3.48 in 2020 to 3.67 in 2021
• The mean number of CCs was lowest for single individuals (3.23) compared to married (3.28)
• Those from low-income areas had higher mean number of CC (3.33) compared to those in the highest income areas (3.19)

Changes in COVID-19 Coding

• Large increase in coding of COVID-19 as a contributing cause between 2020 and 2021 in Ontario, Alberta, and British Columbia.
• Small decrease in coding of COVID-19 as a contributing cause between 2020 and 2021 in Quebec.
• Public health measures carried out in Canada have not only reduced the mortality associated with COVID-19 as an UC but have also changed the structure of associated causes.

Data Sources

We accessed the Canadian Vital Statistics Death Database and Multiple Cause Database through Statistics Canada’s Research Data Centre (RDC). Data accessed through the RDC, which follows strict disclosure protocols in accordance with the Statistics Acts, is exempt from approval by the Research Ethics Board (REB) as per Tri-Council Policy Statement: Ethical conduct for research involving humans (TCPS2) article 2.2 (a).

Funding Sources

Funding for this research was provided by Social Sciences and Humanities Research Council of Canada Insight Grant #435-2021-1052.

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