Hrev_master Abstract We performed an electronic search in CDC WONDER online database (years 2018-2022) to explore whether the higher risk of dying during the weekends may be related to complications of medical and surgical care. One-way ANOVA and Tukey’s HSD multiple comparison test revealed no significant variation in mean number of deaths during the seven days of the week in the US. No significant difference was observed between the mean number of deaths during the weekend and those recorded during the week- days (675±130 vs. 711±112; p=0.339). The mean ratio of mortality due to complications of medical and surgical care to the total num- ber of deaths was not significantly different on weekends and weekdays (151 vs. 158×100,000 deaths; p=0.255). The results of this analysis suggest that the so-called “weekend effect” may not be apparently attributable to complications of medical and surgical care and may hence be more related to patient-specific factors. Introduction Reliable evidence has been provided that the risk of unfavor- able outcomes for hospitalized patients may not be evenly distribut- ed across the seven days of the week, resulting in a higher risk of death on weekends than during the rest of the week.1 This well- known aspect in healthcare, called as the “weekend effect”, has been attributed to a combination of factors such as reduced medical staffing levels, a tendency of general practitioners to admit more severe patients on Fridays (thereby avoiding problems over the weekend), as well as societal problems such as financial issues, rel- atives’ working patterns, and even selection biases because a lower rate of patients seeking for emergency care on weekends are then admitted to hospital, and so forth.2 We hence planned a short study to explore whether the “weekend effect” may also be related to a significant burden of complications of medical and surgical care. Materials and Methods We conducted an electronic search in the most recent version of the US Centers for Disease Control and Prevention (CDC) WONDER online database (years 2018-2022),3 which provides mortality data for US citizens across locations and over time. The search was expanded to the available five years (2018-2022), for total mortality or using specific International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10) codes Y40-Y84, which include all “complica- tions of medical and surgical care” stratified by day of the week (Table 1).4 Mortality data were reported as the mean number of deaths ± Standard Deviation (SD) over the four years. Data were graphically plotted in Microsoft Excel (Microsoft, Redmond, WA, USA) and analyzed using one-way ANOVA and the Tukey’s hon- estly significant difference test (Tukey’s HSD; StatsDirect, StatsDirect Limited, Birkenhead Wirral, UK). Statistical signifi- cance was determined at p<0.05. The study was performed in accordance with the Declaration of Helsinki and under the terms of local legislation. Results Figure 1 summarizes the results of our analysis. Although there was an apparent trend of increased mortality for complications of medical and surgical care in the middle of the week and a visible decline on Sundays, the one-way ANOVA revealed no significant variation (F-statistics: 0.183; p=0.979; Figure 1A). Overall, the mean number of deaths for complications of medical and surgical care was 699±114 on Mondays, 706±90 on Tuesdays, 719±119 on Wednesdays, 716±123 of Thursdays, 718±124 on Fridays, 703±126 on Saturdays and 646±135 on Sundays. The Tukey’s Emergency Care Journal 2024; volume 20:12949 [Emergency Care Journal 2024; 20:12949] [page 125] No evidence of “weekend effect” for complications of medical and surgical care Camilla Mattiuzzi,1 Giuseppe Lippi2 1Medical Direction, Rovereto Hospital, Provincial Trust for Social and Sanitary Services (APSS), Trento; 2Section of Clinical Biochemistry, University of Verona, Verona, Italy Correspondence: Giuseppe Lippi, Section of Clinical Biochemistry, University Hospital of Verona, Piazzale L.A. Scuro, 10, 37134 Verona, Italy. Tel.: +39.045.8122970 - Fax. +39.045.8124308 E-mail: giuseppe.lippi@univr.it Key words: mortality; medical errors; complications; weekend. Funding: this article received no funding Conflict of interest: the authors declare that they have no conflict of interest. Ethics approval and consent to participate: not applicable. Availability of data and materials: all data generated or analyzed during this study are included in this published article. Received: 21 August 2024. Accepted: 28 September 2024. Early view: 15 October 2024. This work is licensed under a Creative Commons Attribution 4.0 License (by-nc 4.0). ©Copyright: the Author(s), 2024 Licensee PAGEPress, Italy Emergency Care Journal 2024; 20:12949 doi:10.4081/ecj.2024.12949 Publisher's note: all claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher. Non -co mmerc ial us e o nly HSD multiple comparison test also revealed no significant differ- ence between multiple comparisons of mortality for complications of medical and surgical care across the different days of the week (all p>0.989). No statistically significant difference was also observed when the mean number of deaths for complications of medical and surgical care during the weekend (675±130) was com- pared to that recorded during the weekdays (711±112; p=0.339). Overall mortality in the US is also shown in Figure 1B. There was no statistically significant trend (F-statistic: 0.040; p=0.999). Again, no statistically significant difference was found when the mean number of total deaths on weekends (449592±36969) was compared to weekdays (453007±38384; p=0.451). Accordingly, the mean ratio of mortality due to complications of medical and surgical care to the total number of deaths in the US was not sig- nificantly different on weekends and weekdays (151 vs. 158×100,000 deaths; p=0.255). Discussion The seminal study published by Bell and Redelmeier in 2001,5 including nearly 4 million Canadian patients over a 10-year period, paved the way to the definition of the so-called “weekend effect”, in that the authors found that several causes of death were associ- ated with a higher risk of mortality during the weekends. These results were then confirmed in several other studies, as recently meta-analyzed by Pauls and colleagues.1 For example, in the large study by Walker et al. in 2017,6 the authors found that the 30-day mortality of patients emergently admitted on a weekend was higher than that of those emergently admitted on a weekday (5.1 vs. 4.7%; p<0.001). The authors also found that adjusting mortality rates for routine test results effectively reduced the excess mortality associ- ated with weekend and holiday emergency admissions. Regardless of this apparently straightforward phenomenon, the underlying causes remain largely enigmatic. One possible explanation that has been given, is an insufficient medical staffing level during the weekends, both in terms of quantity and quality, which may hence be associated with increased risk of complications or even mal- practice.2 Nonetheless, the results of our analysis on the last online version of the CDC WONDER database provide evidence that the so-called “weekend effect” may not be apparently attributable to complications of medical and surgical care, and may hence be more related to patient-specific factors. Nevertheless, equalization of hospital resources for emergency admissions on all days of the week in many countries remains a very important public health issue. Notably, not all deaths attributable to suboptimal care are necessarily coded as such. For example, an inexperienced physi- cian might not recognize that his or her inexperience contributed to a patient’s death. Similarly, hospital understaffing is unlikely to be considered a sufficient reason for coding a death as Y40-Y82, although it may well be the cause of delayed or inappropriate care. Brief Report Table 1. International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10)3 codes encompassing the generic definition of “complications of medical and surgical care” used in this analysis. ICD-10 Code Description Y40-Y59 Drugs, medicaments and biological substances causing adverse effects in therapeutic use Y60-Y69 Misadventures to patients during surgical and medical care Y70-Y82 Medical devices associated with adverse incidents in diagnostic and therapeutic use Y83-Y84 Surgical and other medical procedures as the cause of abnormal reaction of the patient, or of later complication, without mention of misadventure at the time of the procedure [page 126] [Emergency Care Journal 2024; 20:12949] Figure 1. Mean number of deaths (with standard deviation; SD) for complications of medical and surgical care (A) and total num- ber of deaths (B) in the US during the years 2018-2022, stratified according to the day of the week. The results of the statistical analysis are provided in the text of the manuscript. Non -co mmerc ial us e o nly References 1. Pauls LA, Johnson-Paben R, McGready J, et al. The Weekend Effect in Hospitalized Patients: A Meta-Analysis. J Hosp Med 2017;12:760-6. 2. Mathew A, Fyyaz SA, Carter PR, et al. The enigma of the weekend effect. J Thorac Dis 2018;10:102-5. 3. Centers for Disease Control and Prevention, National Center for Health Statistics. National Vital Statistics System, Mortality 2018-2022 on CDC WONDER Online Database, released in 2024. Data are from the Multiple Cause of Death Files, 2018-2022, as compiled from data provided by the 57 vital statistics jurisdictions through the Vital Statistics Cooperative Program. Available from: http://wonder.cdc.gov /ucd-icd10-expanded.html on Sep 13, 2024. 4. World Health Organization. (2015). International statistical classification of diseases and related health problems, 10th revision, Fifth edition, 2016. World Health Organization. https://iris.who.int/handle/10665/246208 5. Bell CM, Redelmeier DA. Mortality among patients admitted to hospitals on weekends as compared with weekdays. N Engl J Med 2001;345:663-8. 6. Walker AS, Mason A, Quan TP, et al. Mortality risks associated with emergency admissions during weekends and public holi- days: an analysis of electronic health records. Lancet 2017;390:62-72. Brief Report [Emergency Care Journal 2024; 20:12949] [page 127] Non -co mmerc ial us e o nly