Determining the investors' strategy during the COVID-19 crisis based on the S&P 500 stock index1

Background: The most significant changes caused by the COVID-19 crisis were the sharp increase in working from home and the growing importance of e-commerce, which affected the development of some industries. This change also affects the investors' investment operations, which are based on analysis to ensure an unquestionable certainty of the invested financial amount and a satisfactory return. It is, therefore, interesting to analyze the possible return of the chosen investment strategy based on the optimization model of portfolio selection based on the CVaR risk measure. Purpose: The paper aims to present the possible use of the analysis of returns of effective portfolios constructed based on the optimization model of portfolio selection based on the CVaR risk measure during the crisis (COVID-19) and the pre-crisis period. Study design/methodology/approach: Paper presents the impact of the COVID-19 crisis on investor decision-making through the CVaR risk measure, which was implemented on the historical data of the components of the Standard and Poor's 500 stock index (S&P 500) in the crisis period as well as in the pre crisis period. Findings/conclusions: The presented approach based on the CVaR risk rate measure and the relevant portfolio selection model provides the investor with an effective tool for allocating funds to the financial market in particular segments in both monitored periods. Limitations/future research: Time series data are divided into two periods based on visible factors such as the number of COVID-19 cases. In future research, we aim to divide monitored periods based on unobservable factors influencing investors' decisions, such as bull or bear mood on the market.

Hair cortisol concentrations in medical nurses during the COVID-19

Background: The COVID-19 pandemic is a serious and long-term stressor for healthcare workers, therefore hair cortisol concentrations (HCCs) could be used to assess this prolonged stress. Method: HCCs of 67 female nurses were measured during spring 2020, with a follow-up performed in autumn 2020 with 57 participants. Both times, HCCs were analyzed from two 3 cm hair segments corresponding to periods of hair growth before and during the spring wave of the pandemic, during the summer release, and the autumn wave of the pandemic. Results: Data from spring 2020, showed higher HCCs in hair grown during the pandemic compared to older hair (90%CI η2=0.123-0.397), while nurses reporting a high risk of infection (n=33) had higher HCCs (90%CI η2=0.002-0.176) than nurses reporting low risk (n=34). In the follow-up, hair samples corresponding to worsening of the pandemic had higher HCCs than samples from summer release (90%CI η2=0.002-0.201). Three groups were compared instead of two, as only 9 nurses reported low risk, 25 high risk, and 23 daily work with COVID-19 patients. Group differences were not significant. Conclusion: Data from the follow-up supported the findings of higher HCCs in nurses during the worsening of the pandemic.