key: cord-0940659-c2zncbww
authors: Postill, G.; Murray, R.; Wilton, A.; Wells, R. A.; Sirbu, R.; Daley, M. J.; Rosella, L. C.
title: An analysis of mortality in Ontario using cremation data: Rise in cremations during the COVID-19 Pandemic
date: 2020-07-24
journal: nan
DOI: 10.1101/2020.07.22.20159913
sha: 4fe288282f25678f488263e4515a0b9943314152
doc_id: 940659
cord_uid: c2zncbww

Background: The impact of coronavirus disease 2019 (COVID-19) on all-cause mortality in Ontario is unknown. Cremations are performed for most deaths in Ontario and require coroner certification before the cremation can take place. Our objective was to provide timely analysis of deaths during the COVID-19 pandemic using cremation data. Methods: This study describes cremation certificate data from January 1, 2017, to May 31, 2020, in Ontario. Cremation records during 2020 were compared to historical records from 2017-2019, grouped according to age, month, and place of death and further stratified by COVID-19 involvement. A time series model was fit to quantify the deviation in cremation trends during the COVID-19 period. Results: There have been 33 834 cremations in Ontario in 2020, and 20 898 (62%) took place from March onwards. In April, which saw the peak number of COVID-19 cases, had an additional 1,830 cremations compared to historical averages over 2017-2019, representing a 32% increase (3 871 in 2020). Time series modelling of cremations in Ontario from January 2017 demonstrated that cremations in March, April, and May 2020 exceeded the predicted increase based on modelled estimates. Even without the COVID-19 deaths, the seasonal and numerical trends for 2020 are substantially different from the historical period. Interpretation: Cremations were higher in the months during the pandemic compared to previous years. These early estimates of mortality are critical for understanding the impact of COVID-19. This study has demonstrated the utility of cremation data to provide timely mortality information during a public health emergency.

The 2019 novel coronavirus (SARS-CoV-2) has given rise to the severe COVID-19 disease around the world. COVID-19 has had a significant impact on health systems and mortality globally. While the impact on hospitalizations and intensive care units is routinely tracked, mortality data is less consistent, given the variation in how mortality data are captured. Quantifying the effect of COVID-19 on allcause mortality is a critical element needed to inform the policy response.

In Canada, the responsibility of death recording and reporting deaths lies with the provinces and territories, according to the Vital Statistics Act. 1 There are several challenges with obtaining real-time mortality data given the need to verify the record and cause of death, which can take months or years. Although COVID-19 mortality has been reported in Ontario through public health databases, two of the number of deaths from other causes is not yet available as the routine verification process that results in data lags exceeding a year. Without all-cause mortality information, the data on COVID-19 specific mortality is difficult to contextualize. Further, there remain critical questions regarding the mortality during the pandemic from all causes given restrictions to medical care and other consequences of largescale shutdowns. 2 Several other countries have reported increases in morality during the COVID-19 period; [3] [4] [5] however, the extent of this effect in Canada is unknown and required to inform both healthcare and public health responses.

In Ontario, in recent years, cremations are performed for about 70% of deaths. 6 Before cremation can occur, a coroner's certification is needed. 7 ; as a result, cremation data are available in near-real-time and offers a consistent data source to examine these mortality trends in a timelier manner. Cremation data has been used in other countries to quantify the mortality trends during the COVID-19 pandemic. 8 Our goal was to estimate the COVID-19 mortality from cremation data across age and place of death and to quantify the difference in those trends by comparing them to historical cremation records for 2017-2019 to generate the earliest analysis of mortality during the pandemic in Ontario.

In Ontario, Canada, a Cremation Certificate must be provided by a coroner to authorize the cremation of a deceased person. 7 A licensed crematorium operator cannot proceed without a Cremation Certificate. The law in Ontario requires that a coroner review the circumstances surrounding the death before cremation takes place. The review and authorization are documented on the certificate and kept on file at the crematorium. 1 Since 2017. These records have been collected and stored electronically by the Office of the Chief Coroner for Ontario. This database contains names, dates of birth and death, location of death, and cause of death for every person cremated in the province since that time. Records submitted until June 19 with dates of death before June 12020 were included. All cremations were deidentified and maintained in an electronic database for the analysis. Records with a cause of death specified as 'test' or age at death greater than 120 were excluded.

The records were categorized according to the month of death and subcategorized by age and type of facility in which death occurred. Age in the file is a numerical field, which was converted into a categorical vector (0-44 years, 45-74 years, and 75+ years). The facility at death is reported as either long-term care, hospital, residence, or other. The stratified monthly difference in 2020 cremations relative to the average number of cremations by month in 2017-2019 was calculated as both the absolute difference and percent increase.

The 2020 COVID-19 related deaths were isolated from the 2020 records by the presence of the terms COVID or novel coronavirus as the cause of death, antecedent cause, or other cause categories. These were the only terms found to describe COVID in the cremation records. Records that matched the above criteria but also contained the following phases, test-results pending, possible, and negative, were excluded from the classification of death due to COVID-19.

The number of weekly cremations (Monday to Sunday) was determined for 2017, 2018, and 2019 to demonstrate the expected annual seasonality in the number of cremations. Their respective trends were smoothed using the Statsmodel Holt's package; the default additive model was changed to an exponential model with a fixed smoothing slope (β = 0.2) and smoothing level (α = 0.6). Exponential smoothing was used as the data was demonstrated with the Augmented Dickey-Fuller Test to be nonstationary (ADF Test Statistic of -2.499 with a P-Value 0.116). The number of weekly cremations for 2020 was tabulated both with and without COVID-19 deaths to determine the variance in cremations with and without COVID-19.

Using the daily cremation counts from January 2017, a time series model was fit with FB Prophet, an automated additive regression model with adjustable parameters. The parameters used in the model were a logistic growth curve and a yearly seasonality component. The yearly seasonality component was estimated with a partial Fourier sum of order 10. The flexibility of the trend was increased by adjusting the change point parameter to 0.15, and the confidence interval was set to 95%. Outliers were not removed due to the limited number of data points. The following 365 days (2020) were forecasted to determine the expected number of cremations for 2020. The actual values for weekly cremations were overlaid on the time series to compare. All analysis was done using Python 3.7.0.

Of the 268,176 cremation records analyzed, 234 had missing data for cause of death, 4267 records had missing age at death, and 180 had a missing facility of death. Cremations by month and age are shown in Table 1 . Overall, there have been 33,834 cremations in the year 2020. 20,969 (62%) took place in March, April, and May, corresponding to the pandemic period in Ontario. The highest number of cremations (N=7,518) were observed in the month of April, which was also when the most COVID-19 cases were confirmed (N=14,435 cases). The majority of the April cremations (63%, N=4,749 occurred in the 75 and older age group) and demonstrated the highest increase compared to the 2017-19 baseline (38%). The number of cremations in both January and February showed small increases over the 2017-2019 average for each age of death category (2.3% and 4.5% respectively). In contrast, the numbers of cremations in March, April, and May differed substantially from the 2017-2019 historical averages with an 8.4% increase in March, a 32% increase in April and a 20% increase in May of 2020 (Table 1 ). In Ontario, more than 70% of deaths proceed to cremation, with higher percentages in those aged 55 and older and smaller numbers in the younger ages (<19 years) (Supplement Figure 1 ).

The distribution of facility of death for individuals cremated in Ontario also shifted during 2020. The differences in all-cause cremation numbers vary by the facility of death and by month such that the greatest differences were seen in long-term care homes in the month of April (89% increase compared to April in the 2017-19 period), which was also the month with the highest numbers of confirmed COVID-19 deaths reported by public health (N=1,399) . Notably, the increase in cremations for deaths occurring at home was also substantially higher in March (23%) and April (68%) (Figure 1 ) and most of the cremations in April were among deaths in long-term care settings (Supplement Figure 2) . A . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted July 24, 2020. . https://doi.org/10.1101/2020.07.22.20159913 doi: medRxiv preprint similar number of cremations from deaths occurring in hospitals during 2020 was seen compared to historical averages; however, the distribution of deaths occurring in long-term care and in residences was higher in the 2020 period compared to 2017-2019 (Supplement Figure 3) .

A time-series methodology was used and demonstrated that the number of daily cremations for March, April, and May 2020 exceeded the predicted increase of our time series model with 95% CI bounds, as illustrated in Figure 3 . The model demonstrated that there had been an overall increase in the number of cremations in Ontario.

Weekly cremation trends separating deaths related to COVID-19 are shown in Figure 4 . COVID-19 deaths are elevated and account for a substantial proportion, but not all, the increase seen in April and May. Even excluding COVID-19 deaths, the monthly trends for 2020 are substantially different from 2017, 2018, and 2019 exponentially smoothed trends shown in Figure 4 .

This is the first study to provide estimates of mortality trends for Ontario during the COVID-19 pandemic and to demonstrate the utility of cremation data in monitoring mortality. Our results identify a significant increase in the number of cremations during March, April and May of 2020, which coincide with COVID-19 activity in Ontario. While COVID-19 deaths are routinely reported, monitoring all-cause mortality is an important metric, critical to contextualizing these numbers and understanding the full impact of COVID-19 in the population. The strengths of the study are the inclusion of all cremations up to the end of May 2020 (not currently available for any other mortality data) and the inclusion of all-cause mortality in addition to COVID-19 deaths.

The results demonstrate an apparent increase in all-cause cremations during the months where the number of COVID-19 cases was highest in Ontario. The observed increases far exceed those predicted according to the time series model. This supports findings from many other regions in the world, reporting excess mortality during the COVID-19 pandemic. 3 4 As found in other studies, not all of the mortality increase was due to COVID-19 deaths alone. Estimates from other jurisdictions attribute 50-80% of the rise due to COVID-19 directly, five, which was consistent with what was observed in the cremation data. There are several reasons why non-COVID-19 deaths may also increase including delay in emergency 9 and routine medical care for cardiovascular 10 and other conditions 11 as well as other factors such as fears of dying in isolation in hospital. 12 We noted a substantial increase in the number of cremations deaths occurring from deaths in long-term care, which is consistent with the high burden of COVID-19 in this population. 13 14 We also noted an increase in the number and proportion of deaths occurring in personal residence compared to the portion of deaths seen in hospitals in previous years. This indicates an increase in the mortality was not exclusively seen in long-term care.

A portion of the observed increase in late March and early April 2020 may be due to under-recognition of COVID-19 mortality early in the pandemic. Furthermore, there could be an under-recognized number of COVID-19 deaths throughout the pandemic period due to a lack of testing or false-negative test results. 15 The variation in April and May 2020 could be due to several factors, including a shift toward cremation over burial in response to restrictions on travel, social gatherings, finances, or an increase in all-cause mortality secondary to COVID-19 pandemic response and wide-spread societal, health, and social service changes. As Ontario maintained social gathering restrictions and a state of . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted July 24, 2020. . emergency in May, the spike in cremations in April and subsequent decline in May supports an increase in all-cause mortality due to other factors such as delayed medical care, the loss of employment/income, 16 isolation, and/or under-recognition of COVID-19 mortality.

There are some important limitations to this analysis that should be considered. First, specific cause-of death data were not included because of the nature of the data structure (open text fields) and the heterogeneity in classification of cause of death as immediate and antecedent, which prevents rapid analysis. Additional cremation records may be recorded for the 2020 time period, but this is not expected to change the findings reported in this study. As discussed, while cremation data represent most deaths in Ontario, they do not represent all deaths. Certain segments of the population may be more or less likely to be cremated. This would be an issue in the comparison if the number of deaths during the pandemic period was affected disproportionately in a group with an intrinsically higher or lower rate of cremation (e.g. age group, burial traditions, geographic regions). Therefore, we must acknowledge that at least some of the changes observed may be due to changes in preferences for cremation during the pandemic. However, we do not anticipate this to be the main reason for the increase given the high numbers of cremations before the pandemic and the congruence of the increases with the peak pandemic activity. The relationship between cremation numbers and overall mortality will be verifiable when vital statistics data for this period becomes available.

In summary, the number of cremations was significantly higher during the peak pandemic period in Ontario compared to previous months and historical averages. This study documents the first changes in mortality during COVID-19 pandemic in Ontario and these data will continue to be important to inform the ongoing COVID-19 pandemic response. All-cause mortality data is a critical data source describing the population impact of COVID-19 in Canada and this study has demonstrated the utility of cremation data to provide more timely mortality information during a public health emergency. Sustained monitoring of mortality trends from all data resources over the course of pandemic, including subsequent waves, is needed.

. CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity.

The copyright holder for this preprint this version posted July 24, 2020. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted July 24, 2020. . CC-BY-NC-ND 4.0 International license It is made available under a is the author/funder, who has granted medRxiv a license to display the preprint in perpetuity. (which was not certified by peer review)

The copyright holder for this preprint this version posted July 24, 2020. . https://doi.org/10.1101/2020.07.22.20159913 doi: medRxiv preprint

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The authors acknowledge Dr. Dirk Huyer, Chief Coroner for Ontario for the