Diurnal Variation in the Mortality of Patients with COVID-19 Pneumonia: A Retrospective Study

Abstract

Introduction: Coronavirus Disease 2019 (COVID-19), the new contagious novel coronavirus, Severe Acute Respiratory Syndrome Coronavirus 2 (SARS‑CoV‑2), pandemic in 2020-21 has had a devastating impact on human race. The most common cause of death among hospitalised patient was COVID-19 pneumonia or lung injury. Various studies have shown diurnal variation in human mortality due to all causes with or without intervention. Aim: To identify existence of diurnal variations for mortality among the hospitalised patients with COVID-19 pneumonia. Materials and Methods: This hospital-record based, retrospective study was conducted in a tertiary referral centre of north-east India (Assam Medical College, Dibrugarh, Assam, India) which was a dedicated COVID-19 hospital during the pandemic. The study was conducted from September 2021 to December 2021 and the data was collected and recorded from the Cadaver slips issued to families of patient dying of COVID-19 pneumonia during the period January 2021 to August 2021. The data were generated by plotting the number of deaths of COVID-19 cases for each two hour interval as a percent of the mean number of deaths per two-hour interval and as a percentage of cumulative deaths per two-hour interval on a 24 hour scale. The deaths were sub grouped according to gender, age, and reported co-morbid causes of death along with pneumonia. Comparisons of data i.e., mean deaths/2 hour interval (mean±SD) were performed by one-way Analysis of Variance (ANOVA), followed by Bartlett’s test for equal variances. The p-value <0.05 was considered as statistically significant. Results: Total 743 deaths, with 537 males and 206 females were included in the study. Mean age of the deaths was 56.01 years. There was rise of deaths during 4 PM-6 PM (16:00-18:00) interval for all deaths due to COVID-19 pneumonia. The increase in deaths during this period mainly accounted for males equal or above 65 years and females below age 65 years. However, the deaths of females equal or above the age of 65 years did not show significant diurnal variation. Only 26.51% (n=197) of pneumonia deaths were without co-morbidity. Conclusion: There exists a diurnal variation in mortality among COVID-19 pneumonia patients with evening rise of deaths. Diurnal variation is significantly more among males rather than females above 65 years.

Keywords

• circadian rhythm
• coronavirus disease 2019
• severe acute respiratory syndrome coronavirus 2
• time of death