Table 2C.

Overview of the characteristics of the studies answering Q5 and Q6.

Author	Study design	Sample size (studies, total sample size)	Measurement instruments	Key findings
de Vroege et al. (4)	Survey	N = 1372		Q5.— Q6. 11.3% agreed and 9.0% agreed that they were taking more sick leave. 7.5% agreed and 12.4% agreed that they should take more leave. Between 7.8% (partly agree) and 8.8% (agree) say they are more absent during the pandemic. 7.5% of respondents said they would consider working less and 4.2% said they would consider stopping working in a nursing home
Moloney et al. (32)	Integrative review	20 studies		Q5. Sustainability and organizational effectiveness through healthy, high-performing and engaged employees Q6. Internationally, nursing is faced with unsustainable working conditions, high staff turnover and staff stress factors that hinder effective care and negatively impact health outcomes. The workload of nurses is often heavy and demanding, leaving them physically and mentally exhausted. Nurses are more prone to injuries and physical illness than the general public due to stress, burnout and psychological imbalances, and are more prone to mental illness than the general public. A severe shortage of nurses is expected, which will increase the demand for surplus nurses and increase staff shortages and the willingness to leave. COVID-19 has exacerbated these problems.
Roczniewska and Richter (33)	Multilevel analysis	N = 269	Job Demands-Resources model (JDR-model)	Q5. Sustainable employability (SE) is defined as the opportunity for employees to make valuable contributions through their current and future jobs, while maintaining their health and wellbeing. SE includes good physical and mental health and wellbeing at work (job satisfaction). Q6. Hypothesis 1. Vertical trust at the individual level is positively associated with SE, namely (a) job satisfaction, (b) health and (c) job performance. Hypothesis 2. Team-level teamwork is positively associated with SE, i.e. (a) job satisfaction, (b) health and (c) job performance. Hypothesis 3. Transformational leadership at group level is positively associated with sustainable employability, i.e., (a) job satisfaction, (b) health and (c) job performance.
Schouten et al. (34)				Q5. — Q6. In particular, physical (lifting, standing) and mental stress (violence and aggression by third parties) and the use of harmful substances are important factors that explain the decline in sustainable employability.
Smyth and Pit (35)	Qualitative study	N = 19	Work ability (WA) model	Q5. Sustainable employability means that employees can realize tangible opportunities in the form of a range of competencies during their working lives. They also enjoy conditions that allow them to make a valuable contribution through their current and future work, while maintaining health and wellbeing. This requires on the one hand a suitable work environment for them and on the other hand the attitude and motivation to take advantage of these opportunities. An individual's SE is defined as the long-term ability to obtain, create, and retain work by adapting to changing employment, economic, and personal circumstances at different stages of life. Q6. A balance between lifestyle and work leads to better physical health (first floor) and a better attitude to work.
Van Dorssen-Boog et al. (36)	Project	N = 109	JDR-model	Q5. Employees are sustainable if they are not only able and willing to meet the demands of their current job, but also remain competent and motivated to remain productive throughout their working lives. Q6. We expect a virtuous cycle to increase motivation, vitality, health, and productivity as employees and teams learn to use resources more effectively such as autonomy, social support, and their own and others' strengths. In addition, we expect fewer negative outcomes such as burnout, absenteeism, and staff turnover/dismissal. Effective self-leadership behavior goes hand in hand with positive and constructive thinking.

Q1; mental health problems amongst HCW before the COVID-19 pandemic, Q2; prevalence of mental health problems amongst HCW before the COVID-19 pandemic, Q3; mental health issues amongst HCW as a result of the COVID-19 pandemic, Q4; prevalence of mental health issues amongst HCW as a results of the COVID-19 pandemic, Q5; sustainable employability of HCW in healthcare, Q6; the relationship between mental health of HCW and SE in healthcare.