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James N, Menzies M. Nonlinear shifts and dislocations in financial market structure and composition. CHAOS (WOODBURY, N.Y.) 2024; 34:073116. [PMID: 38980379 DOI: 10.1063/5.0209904] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/24/2024] [Accepted: 06/17/2024] [Indexed: 07/10/2024]
Abstract
This paper develops new mathematical techniques to identify temporal shifts among a collection of US equities partitioned into a new and more detailed set of market sectors. Although conceptually related, our three analyses reveal distinct insights about financial markets, with meaningful implications for investment managers. First, we explore a variety of methods to identify nonlinear shifts in a market sector structure and describe the mathematical connection between the measure used and the captured phenomena. Second, we study a network structure with respect to our new market sectors and identify meaningfully connected sector-to-sector mappings. Finally, we conduct a series of sampling experiments over different sample spaces and contrast the distribution of Sharpe ratios produced by long-only, long-short, and short-only investment portfolios. In addition, we examine the sector composition of the top-performing portfolios for each of these portfolio styles. In practice, the methods proposed in this paper could be used to identify regime shifts, optimally structured portfolios, and better communities of equities.
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Affiliation(s)
- Nick James
- School of Mathematics and Statistics, University of Melbourne, Melbourne, Victoria 3010, Australia
- Melbourne Centre for Data Science, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Max Menzies
- Beijing Institute of Mathematical Sciences and Applications, Beijing 101408, China
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Ferreira DP, Bolognani CV, Santana LA, Fernandes SES, de Moraes MSF, Fernandes LAS, de Oliveira DQ, de Santana RB, Gottems LBD, Amorim FF. Impact of the COVID-19 Pandemic on Elective and Emergency Surgeries, and Postoperative Mortality in a Brazilian Metropolitan Area: A Time-Series Cohort Study. Risk Manag Healthc Policy 2024; 17:1701-1712. [PMID: 38946840 PMCID: PMC11214554 DOI: 10.2147/rmhp.s459307] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2024] [Accepted: 06/13/2024] [Indexed: 07/02/2024] Open
Abstract
Purpose The COVID-19 pandemic posed a worldwide challenge, leading to radical changes in surgical services. The primary objective of the study was to assess the impact of COVID-19 on elective and emergency surgeries in a Brazilian metropolitan area. The secondary objective was to compare the postoperative hospital mortality before and during the pandemic. Patients and Methods Time-series cohort study including data of all patients admitted for elective or emergency surgery at the hospitals in the Public Health System of Federal District, Brazil, between March 2018 and February 2022, using data extracted from the Hospital Information System of Brazilian Ministry of Health (SIH/DATASUS) on September 30, 2022. A causal impact analysis was used to evaluate the impact of COVID-19 on elective and emergency surgeries and hospital mortality. Results There were 174,473 surgeries during the study period. There was a reduction in overall (absolute effect per week: -227.5; 95% CI: -307.0 to -149.0), elective (absolute effect per week: -170.9; 95% CI: -232.8 to -112.0), and emergency (absolute effect per week: -57.7; 95% CI: -87.5 to -27.7) surgeries during the COVID-19 period. Comparing the surgeries performed before and after the COVID-19 onset, there was an increase in emergency surgeries (53.0% vs 68.8%, P < 0.001) and no significant hospital length of stay (P = 0.112). The effect of the COVID-19 pandemic on postoperative hospital mortality was not statistically significant (absolute effect per week: 2.1, 95% CI: -0.01 to 4.2). Conclusion Our study showed a reduction in elective and emergency surgeries during the COVID-19 pandemic, possibly due to disruptions in surgical services. These findings highlight that it is crucial to implement effective strategies to prevent the accumulation of surgical waiting lists in times of crisis and improve outcomes for surgical patients.
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Affiliation(s)
| | - Claudia Vicari Bolognani
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
| | - Levy Aniceto Santana
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
| | - Sergio Eduardo Soares Fernandes
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
| | | | | | | | | | - Leila Bernarda Donato Gottems
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
| | - Fabio Ferreira Amorim
- Graduation Program in Health Sciences, University of Brasília (Unb), Brasília, Brazil
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
- Graduation Program in Health Sciences of School Health Sciences, Escola Superior de Ciências da Saúde (ESCS), Brasília, Brazil
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Tian S, Huang W. The causal relationship between gut microbiota and COVID-19: A two-sample Mendelian randomization analysis. Medicine (Baltimore) 2024; 103:e36493. [PMID: 38306556 PMCID: PMC10843424 DOI: 10.1097/md.0000000000036493] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 11/15/2023] [Indexed: 02/04/2024] Open
Abstract
Recent studies have shown that gut microbiota is associated with coronavirus disease 2019 (COVID-19). However, the causal impact of the gut microbiota on COVID-19 remains unclear. We performed a bidirectional Mendelian randomization. The summary statistics on the gut microbiota from the MiBioGen consortium. Summary statistics for COVID-19 were obtained from the 6th round of the COVID-19 Host Genetics Initiative genome-wide association study meta-analysis. Inverse variance weighting was used as the main method to test the causal relationship between gut microbiota and COVID-19. Reverse Mendelian randomization analysis was performed. Mendelian randomization analysis showed that Intestinimas.id.2062 was associated with an increased risk of severe COVID-19. Bifidobacterium.id.436, LachnospiraceaeUCG010.id.11330, RikenellaceaeRC9gutgroup.id.11191 increase the risk of hospitalized COVID-19. RuminococcaceaeUCG014.id.11371 shows the positive protection on hospitalized COVID-19. There is no causal relationship between gut microbiota and infection with COVID-19. According to the results of reverse Mendelian randomization analysis, no significant causal effect of COVID-19 on gut microbiota was found. The study found that gut microbiota with COVID-19 has a causal relationship. This study provides a basis for the theory of the gut-lung axis. Further randomized controlled trials are needed to clarify the protective effect of probiotics against COVID-19 and the specific protective mechanisms. This study has important implications for gut microbiota as a nondrug intervention for COVID-19.
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Affiliation(s)
- Siyu Tian
- Proctology Department, School of Clinical Medicine, Chengdu University of Traditional Chinese Medicine, Chengdu, China
| | - Wenhui Huang
- Cardiothoracic Surgery Department, Hospital of Chengdu University of Traditional Chinese Medicine, Chengdu, China
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Ferreira DP, Bolognani CV, Santana LA, Fernandes SES, de Moraes MSF, Fernandes LAS, Pereira CDS, Ferreira GB, Göttems LBD, Amorim FF. Impact of the COVID-19 Pandemic on Births, Vaginal Deliveries, Cesarian Sections, and Maternal Mortality in a Brazilian Metropolitan Area: A Time-Series Cohort Study. Int J Womens Health 2023; 15:1693-1703. [PMID: 38020934 PMCID: PMC10631387 DOI: 10.2147/ijwh.s429122] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2023] [Accepted: 10/23/2023] [Indexed: 12/01/2023] Open
Abstract
Purpose The COVID-19 pandemic posed a worldwide challenge, leading to radical changes in healthcare. The primary objective of the study was to assess the impact of the COVID-19 pandemic on birth, vaginal delivery, and cesarian section (c-section) rates. The secondary objective was to compare the maternal mortality before and after the pandemic. Patients and Methods Time-series cohort study including data of all women admitted for childbirth (vaginal delivery or c-section) at the maternities in the Public Health System of Federal District, Brazil, between March 2018 and February 2022, using data extracted from the Hospital Information System of Brazilian Ministry of Health (SIH/DATASUS) on September 30, 2022. Causal impact analysis was used to evaluate the impact of COVID-19 on birth, vaginal delivery, and c-section using the CausalImpact R package, and a propensity score matching was used to evaluate the effect on maternal mortality rate using the Easy R (EZR) software. Results There were 150,617 births, and considering total births, the effect of the COVID-19 pandemic was not statistically significant (absolute effect per week: 5.5, 95% CI: -24.0-33.4). However, there was an increase in c-sections after COVID-19 (absolute effect per week: 18.1; 95% CI: 11.9-23.9). After propensity score matching, the COVID-19 period was associated with increased maternal mortality (OR: 3.22, 95% CI: 1.53-6.81). The e-value of the adjusted OR for the association between the post-COVID-19 period and maternal mortality was 5.89, with a 95% CI: 2.43, suggesting that unmeasured confounders were unlikely to explain the entirety of the effect. Conclusion Our study revealed a rise in c-sections and maternal mortality during the COVID-19 pandemic, possibly due to disruptions in maternal care. These findings highlight that implementing effective strategies to protect maternal health in times of crisis and improve outcomes for mothers and newborns is crucial.
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Affiliation(s)
- Dilson Palhares Ferreira
- Graduation Program in Health Sciences, University of Brasília (UnB), Brasília, Federal District, Brazil
| | - Cláudia Vicari Bolognani
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
| | - Levy Aniceto Santana
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
| | - Sérgio Eduardo Soares Fernandes
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
| | | | | | - Camila de Sousa Pereira
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
| | | | - Leila Bernarda Donato Göttems
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
| | - Fábio Ferreira Amorim
- Graduation Program in Health Sciences, University of Brasília (UnB), Brasília, Federal District, Brazil
- Department of Research and Scientific Communication, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
- Medical School, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
- Graduation Program in Health Sciences of School Health Sciences, Escola Superior de Ciências da Saúde (ESCS), Brasília, Federal District, Brazil
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