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Abstract
Objective To describe the mental health of perinatal women in five European countries during the third pandemic wave and identify risk factors related to depressive and anxiety symptoms.
Design A cross-sectional, online survey-based study.
Setting Belgium, Norway, Switzerland, the Netherlands and the UK, 10 June 2021–22 August 2021.
Participants Pregnant and up to 3 months postpartum women, older than 18 years of age.
Primary outcome measure The Edinburgh Depression Scale (EDS) and the Generalised Anxiety Disorder scale (GAD-7) were used to assess mental health status. Univariate and multivariate generalised linear models were performed to identify factors associated with poor mental health.
Results 5210 women participated (including 3411 pregnant and 1799 postpartum women). The prevalence of major depressive symptoms (EDS ≥13) was 16.1% in the pregnancy group and 17.0% in the postpartum . Moderate to severe generalised anxiety symptoms (GAD ≥10) were found among 17.3% of the pregnant and 17.7% of the postpartum women. Risk factors associated with poor mental health included having a pre-existing mental illness, a chronic somatic illness, having had COVID-19 or its symptoms, smoking, unplanned pregnancy and country of residence. Among COVID-19 restrictive measures specific to perinatal care, pregnant and postpartum women were most anxious about not having their partner present at the time of delivery, that their partner had to leave the hospital early and to be separated from their newborn after the delivery.
Conclusion Approximately one in six pregnant or postpartum women reported major depression or anxiety symptoms during the third wave of the pandemic. These findings suggest a continued need to monitor depression and anxiety in pregnancy and postpartum populations throughout and in the wake of the pandemic. Tailored support and counselling are essential to reduce the burden of the pandemic on perinatal and infant mental health.
- mental health
- COVID-19
- depression & mood disorders
- anxiety disorders
Data availability statement
All data relevant to the study are included in the article or uploaded as online supplemental information. Researchers can apply for data access for subprojects within the overall aims of the main study.
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
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STRENGTHS AND LIMITATIONS OF THIS STUDY
This study is the first to capture and provide an international overview of perinatal mental health during the third pandemic wave using uniform data collection.
The study measured symptoms of both depression and anxiety based on validated self-reported screening tools.
The study has limitations inherent to all online surveys, including the over-representation of women with high education levels.
Introduction
Up to 20% of pregnant and postpartum women have symptoms of mental illness.1 Moreover, mental health problems tend to increase in the perinatal population in times of crisis.1 2 Therefore, authorities and healthcare providers are concerned and have called on researchers to study the impact of the COVID-19 pandemic on women’s mental health during the perinatal period.3 Prior work has reported that the COVID-19 pandemic has imposed a major mental health burden and an increased risk of depression, anxiety and sleep disturbances in particular subgroups such as pregnant and postpartum women.3 4 However, despite having information about the impact of the first wave of the COVID-19 pandemic, there is much less knowledge on how the consecutive waves have affected the quality of life and mental health in the perinatal population.
Currently, there is mounting evidence that the pandemic disproportionately affects pregnant and postpartum women’s mental health compared with the general population due to fear and concerns about their unborn child or neonate.3 Studies suggest that between 25% and 60% of pregnant and between 24% and 57% of postpartum women have demonstrated moderate to severe depressive symptoms during and after the first wave of the pandemic (online supplemental table 1). A recent meta-analysis investigating the pooled prevalence of mental health symptoms in developed and low/middle-income countries during the first and second wave of the COVID-19 pandemic showed that the overall prevalence of depression, anxiety and stress in the perinatal population was 27%, 33% and 27%, respectively.5 In a previous multinational study conducted in five European countries at the end of the first wave of the pandemic, we found that 13% and 15% of women had depressive symptoms during pregnancy and breast feeding, respectively. Anxiety levels were also high among these groups.6 In another study, pregnant women showed a more pronounced increase in depression and anxiety than non-pregnant women as the pandemic progressed; pregnant women reported 33% of symptoms of moderate and severe depression compared with 10% in the non-pregnant group.7 Several European studies have reported poorer mental health, including pandemic fear, post-traumatic stress, anxiety and depression among perinatal women during the first and second waves of the pandemic (online supplemental table 1). However, these studies only investigated the prevalence of anxiety and depressive symptoms after the first two pandemic waves and mainly included one country and small sample sizes.
Supplemental material
Ensuring the mental health of the perinatal population is essential for the well-being of mother and child, with potentially severe consequences if neglected.8 This may be particularly true during a pandemic with multiple consecutive waves. Therefore, it is essential to investigate the risk and protective factors associated with the mental health of pregnant and postpartum women during all phases of the pandemic to ensure that adequate actions can be taken, if required.
The primary aim of this multinational cross-sectional study was to describe the mental health of pregnant and postpartum women in five European countries during the third wave of the pandemic (summer 2021). The secondary aim was to identify risk factors related to depressive and anxiety symptoms among pregnant and postpartum women. This also included describing which COVID-19-related measures specific to perinatal care women were most anxious about.
Methods
Study design and data collection
This European cross-sectional online study was performed in Belgium, Norway, Switzerland, the Netherlands, and the UK between 10 June 2021 and 22 August 2021. Uniform data collection was performed using anonymous online questionnaires hosted on the KU Leuven survey platform (Qualtrics) and the University of Oslo’s platform (Nettskjema). These questionnaires were modified based on a prior COVID-19 study in 20206 and adapted to this study based on expert feedback from the coauthors. The survey was first developed in English and then translated into five additional languages (French, Dutch, Norwegian, German and Italian). There were two questionnaires, one tailored to pregnant women and the other to postpartum women. A short version of the survey used in this study is available in online supplemental material 1. Country-specific information on the recruitment tools used and internet penetration rates are summarised in online supplemental material 2. An overview of the infection and vaccination rates in each country during the study period is provided in online supplemental material 3.
Pregnant and postpartum women who gave birth in the previous 3 months, aged 18 or older, were eligible to participate.The respondents could access the survey’s web link via banner ads on national websites, research groups’ webpages, self-help groups on social media and pregnancy and postpartum online discussion fora and apps commonly visited by pregnant women or new mothers. All women who completed the postpartum survey, including those who recently ceased breast feeding, were grouped into the ‘postpartum women’ category. The study findings are reported according to the Strengthening the Reporting of Observational studies in Epidemiology (STROBE) guidelines for cross-sectional studies.9
This study focuses specifically on women’s mental health during the pandemic. It is part of an international COVID-19 collaboration to study pregnant and postpartum women’s mental health status, medication use, COVID-19 vaccine willingness, breastfeeding practices and birth experiences during the pandemic.
Measures
Edinburgh Depression Scale
Edinburgh Depression Scale (EDS) was used to measure the depressive symptoms. It is a perinatal-specific, validated self-report 10-item scale with high internal consistency (0.77).10 11 Each item has four options, which are scored 0, 1, 2 or 3, with a total score between 0 and 30. The scale rates the intensity of depressive symptoms over the last 7 days. Major depressive symptoms were defined as having a total EDS score of ≥13. We applied two cut-offs to distinguish between moderate and major depressive symptoms, that is, ≥10 and ≥13. The most conservative cut-off, that is, ≥13 was thereafter used in the association analyses. A score ≥5 on the EDS anxiety subscale (EDS-3A) was considered as high risk for anxiety.10 12 13 This scale was developed in English but has been translated to and has satisfactory validity in Norwegian, Dutch, French, German and Italian.14
Generalised Anxiety Disorder 7-item scale
Anxiety symptoms were measured using the Generalised Anxiety Disorder 7 (GAD-7) scale, a self-report 7-item scale assessing the level of generalised anxiety experienced in the two previous weeks.15 The scale measures the severity of generalised anxiety on a 4-point Likert scale ranging from 0 (not at all), 1 (several days), 2 (more than half of the days) and 3 (nearly every day), with a total score between 0 and 21. Higher scores indicate more generalised anxiety. Total GAD-7 scores were categorised into minimal (0–4), mild (5–9), moderate (10–14) and severe (15–21) anxiety.15 This scale was also available and validated in all of the survey’s languages.16
Sociodemographic, health and reproductive characteristics
Information on sociodemographic characteristics included country of residence, maternal age, relationship and professional status, education level, COVID-19 characteristics and smoking status in pregnancy and post partum. Professional status was categorised into professionally active=employed, and not professionally active=student, homemaker, jobseeker, incapacitated or unemployed. The educational level was categorised into low, medium and high according to national definitions as low=primary education; medium=professional secondary education, technical secondary education, artistic secondary education, general secondary education and high=professional bachelor, academic bachelor, master and/or PhD. Information on reproductive characteristics included parity, planned pregnancy, gestational trimester on study participation, breastfeeding duration and previous breastfeeding experience, if any. Question on parity and pregnancy planning was only limited to pregnant women. Women were asked to report if they had any chronic disease from a list of 10 common chronic somatic illnesses and pre-existing mental illnesses. Moreover, they could also report other chronic diseases in an open-ended question. A chronic illness was considered a condition that already existed before pregnancy. Depression and anxiety disorders were grouped into pre-existing mental illnesses. Asthma, allergy, cardiovascular diseases, diabetes, epilepsy, hypothyroidism and other diseases were grouped into chronic somatic illnesses.
Women’s perinatal experiences and perceptions during the pandemic
The survey also collected data on women’s perceptions of COVID-19 symptoms and severity, pregnancy and postpartum experiences, and thoughts regarding COVID-19, such as COVID-19 restrictions concerning maternity care and delivery, via several questions specifically designed for this study. The survey further included an eight-item question regarding women’s mental health in relation to COVID-19 measures in maternity services and giving birth (eg, isolation, disrupted antenatal appointments). Women could report the frequency of anxiety concerning each COVID-19 measure on a 6-point Likert scale ranging from ‘not at all anxious’ to ‘extremely anxious’, including a ‘not applicable’ option. To present the findings, we grouped ‘slightly anxious’ and ‘anxious’ into one category as ‘anxious’; and ‘very anxious’ and ‘extremely anxious’ as one category as ‘very anxious’. At the end of the survey, women were asked about their experiences relating to the COVID-19 pandemic in an open-ended question. All the responses were inductively categorised under predominant themes such as mental health, vaccination and medication use, using the clinical judgement approach. Some representative mental health-related statements from each country were extracted for this study.
Statistical analyses
First, women’s sociodemographic and health-related factors, scores on the mental health measures and perinatal experiences and perceptions during the pandemic were analysed using descriptive statistics. Second, associations between characteristics of pregnant and postpartum women and major depressive symptoms (EDS ≥13 as a dichotomous outcome) were estimated by univariate and multivariate generalised linear models (GLMs) with logit link (ie, logistic regression); results are presented as crude and adjusted OR with 95% CIs. Since the continuous GAD-7 variable was positively skewed (online supplemental figure 1), associations between covariates and anxiety symptoms (GAD-7) were estimated by GLMs with gamma distribution and log link function. The results are presented as crude and adjusted exponentiated beta coefficients (Exp β) and 95% CI, and interpreted as follows: when the exponentiated beta value is greater than one, then the probability of higher category increases, while if the value is less than one, the probability of higher category decreases. These models were built following the ‘purposeful selection’ approach.17 Candidate variables were first selected in the univariable analyses, based on p<0.1. Then, variables with no role (p>0.1) or yielding a change smaller than 20% in the beta-coefficients of the retained variables were removed. All sociodemographic, health-related and reproductive characteristics were entered as categorical variables in the models. The final adjusted models included statistically significant variables and those yielding a change equal to or greater than 20% in the beta-coefficients.
The potential for multicollinearity was assessed from the variance inflation factor (VIF) for each variable in each model. Using VIF >10 as a threshold value indicative of multicollinearity,18 the results indicated that multicollinearity was not likely to be a problem in this study. Goodness of fit for the models was evaluated using Hosmer-Lemeshow tests for logistic models and by graphing Anscombe residuals for gamma GLMs. Finally, as sensitivity analyses, models accounting for clustering effects at the country level were developed. Missing data were explored. Because missing data were less than 6% for EDS and 7% for GAD-7, and there were no clear patterns of missingness, we conducted a complete case analysis. Data were analysed in RStudio V.4.1.2 (RStudio Team, RStudio PBC, Massachusetts, USA) and Stata V.16.1 (Stata).
Patient and public involvement
Patients or members of the public were not involved in the development of the study aim and outcome measures, the design of the study, the recruitment and conduct of the study.
Results
In total, 5210 women participated in the survey (including 3411 pregnant and 1799 postpartum women) (see table 1). Most respondents were from Norway (69.7% in pregnancy and 61.9% in post partum). The majority of women had a high educational level and were professionally active at study participation, with a high percentage of women working in healthcare (27.0%). About 4.8% of the pregnant and 5.6% of postpartum women had tested positive for COVID-19 since the start of the pandemic. Regarding COVID-19 severity in both groups, pregnant women had more often moderate symptoms (5.4% vs 4.0%) and were more often hospitalised/demonstrated more long-term symptoms (2.1% vs 1.0%). Approximately 20% of postpartum women’s family members had previously tested positive for COVID-19 compared with 15% in the pregnancy group. Overall, 89.1% of the postpartum women were breast feeding at the time of survey completion.
Characteristics of the study participants, n=5210
With regard to comorbidities, pre-existing depression in pregnancy was reported by 1.8% and 1.1% of pregnant and postpartum women, respectively. The proportion of pregnant and postpartum women experiencing pre-existing anxiety was 1.4%. Allergy (18.6% in pregnant and 12.8% postpartum women) and asthma (5.7% in pregnant and 4.1% postpartum women) were the most commonly reported chronic somatic illnesses. Hypothyroidism was higher in pregnant (4.6%) than postpartum women (1.3%). A comparison of participants’ characteristics with general birthing population data is included in online supplemental table 2.
Mental health status of the pregnant and postpartum women
The prevalence of major depressive symptoms (EDS ≥13) was 16.1% and 17.0% in pregnancy and postpartum, respectively. The proportion of pregnant and postpartum women with generalised anxiety symptoms (EDS-3A ≥5) was 30.3% and 34.0%, respectively. Moderate to severe generalised anxiety symptoms (GAD-7 ≥10) were found among 17.3% and 17.7% of the pregnant and postpartum women, respectively (see table 2).
Mental health status of pregnant and postpartum women during the third wave of the COVID-19 pandemic
Factors associated with major depressive and anxiety symptoms
Pregnant women with a pre-existing mental illness who had an unplanned pregnancy and living in the UK were more likely to experience symptoms of major depression (EDS ≥13). In the postpartum group, women with a pre-existing mental illness, who were not breast feeding, who reported having had COVID-19 or symptoms of COVID-19, and living in the UK were more likely to experience symptoms of major depression (EDS ≥13) (see table 3). Having a pre-existing mental illness (adjusted OR: 2.45–4.12 in magnitude) and living in the UK (magnitude of OR: 2.51–2.96) were most strongly associated with major depressive symptoms in both groups.
Factors associated with major depressive symptoms (EDS ≥13) among pregnant and postpartum women
Among pregnant women, having a pre-existing mental or chronic somatic disease, smoking during pregnancy, having an unplanned pregnancy, having had COVID-19 or symptoms of COVID-19, and country of residence were associated with generalised anxiety symptoms. Among postpartum women, generalised anxiety was positively associated with having a pre-existing mental illness or chronic somatic illness and not being professionally active (see table 4). Having a pre-existing mental illness (adjusted Exp(β): 1.49–1.80 in magnitude) or a chronic somatic illness (adjusted Exp(β): 1.80–1.15 in magnitude) were the factors most strongly associated with generalised anxiety symptoms.
Factors associated with generalised anxiety (GAD-7) among pregnant and postpartum women
The results did not change substantially after sensitivity analyses taking into account data clustering by country.
Impact of COVID-19-related measures in maternity care
Among restrictive measures imposed in maternity services, pregnant and postpartum women reported being most anxious about their partner not being present at the time of delivery, having to leave the hospital early and being separated from their newborn infant (see table 5). Conversely, they were the least anxious about the lack of antenatal classes and disrupted antenatal appointments. Representative statements to the open-ended questions related to mental health and well-being are presented in online supplemental table 3. Overall, from these statements, it appeared that women felt more isolated during the pandemic and that being pregnant during the pandemic could have negative impacts (such as emotional distress, panic attacks and fear) on their mental health and well-being.
Women’s level of anxiousness according to different COVID-19-related measures
Discussion
This multinational cross-sectional online study investigated the mental health status of pregnant and postpartum women living across Europe during the third wave of the COVID-19 pandemic.The results show that among five European countries, the prevalence of major depressive symptoms(EDS ≥13) and moderate to severe generalised anxiety symptoms (GAD-7≥10) in the perinatal study population was up to 17.0% and 17.7%, respectively. The prevalence of general anxiety was up to 34.0% on the EDS anxiety subscale (EDS-3A ≥5). Identified risk factors associated with poor mental health include a pre-existing mental or chronic somatic illness, smoking, an unplanned pregnancy, having had COVID-19 or similar symptoms and residential location.
We observed a slightly higher prevalence of major depressive symptoms and anxiety during the third wave of the pandemic compared with the first one.6 This observation should be interpreted bearing in mind that the two studies cannot directly be compared as they were not performed within the same women and were cross-sectional in design.6 The results, however, are consistent with a meta-analysis that reported a higher prevalence of depression and anxiety in the perinatal population later in the pandemic compared with earlier in the pandemic19 (online supplemental table 1). Another recent international meta-analysis with pooled prevalence results from 23 countries and 20 569 participants showed that the prevalence rates of depression and anxiety among pregnant women during the COVID-19 pandemic were up to 31% (95% CI 20% to 42%) and 37% (95% CI 25% to 49%), respectively. Among postpartum women, the prevalence of depression was 22% (95% CI 15% to 29%).20 There are multiple possible explanations for this variability in prevalence rates across studies: (1) differences in methodology, including psychometric properties of the screening tools in different languages or the different cut-off scores used, (2) pandemic-related factors such as differences in public health regulations implemented globally at different times over the last 2 years and (3) and/orthe public’srelianceon the government to restrain the spread of the virus. The tendency towards higher rates of depression in the perinatal population as previously been reported for Spain and Italy (>30% with depressive symptoms) vs countries in the Northern parts of Europe (<20% with depressive symptoms) (online supplemental 2) coincides well with our study’s finding. As a result, more robust region-specific and pregnancy-specific studies are needed to examine perinatal mental health during a pandemic.
Our secondary findings show that pregnant and postpartum women with pre-existing mental illnesses were more likely to report major depressive and anxiety symptoms. This finding is consistent with the existing literature showing increased depression and anxiety symptoms during a pandemic among those with a history of mental illness.21 In addition, the imposed public health regulations during the pandemic and, potentially, the lack of partner support during delivery and heightened anxiety may all contribute to the worsening of pre-existing mental illnesses or negatively affect the entire experience of pregnancy and delivery.22 This finding underscores the importance of a close follow-up of pregnant or postpartum women with pre-existing mental health conditions in the current and future pandemics.
One concerning finding from our study is that women who reported having had COVID-19 or its symptoms more often reported symptoms of major depressive and anxiety symptoms. This may indicate the burden an infection may have on mental health, which may also be true in future waves of the pandemic. However, due to the study’s cross-sectional design, we cannot rule out whether the converse is true, that is, severe depressive symptoms are linked to greater infection susceptibility. Prior literature covering the first pandemic waves has shown that having been infected may induce fear, post-traumatic stress, anxiety and depression, also among perinatal women23 (online supplemental table 1). Considering other risk factors, pregnant women with an unplanned pregnancy exhibited a significant increase in major depressive symptoms and anxiety which is in accordance with another study on similar topic.24
Our findings show that women consider partner support crucial during delivery, particularly during a pandemic with many uncertainties. Yet, many countries heterogeneously imposed public health regulations that excluded or heavily restricted the woman’s partner from the delivery setting.22 23 Thought of being separated from the baby after delivery also had a negative impact on perinatal women. In retrospect, our findings question the mental health impact of such imposed regulations.
Despite an improvement in antenatal care during the third pandemic wave, different international vaccination policies for pregnant and postpartum populations became available, and as knowledge to tackle the virus increased, it gave rise to new concerns. In particular, the emergence of new and potentially more harmful variants for pregnant women may have contributed to maintaining a high burden of the pandemic on perinatal mental health. More studies are still needed to explore the current pandemic’s long-term perinatal and infant mental health consequences.
Strength and limitations
This study measured symptoms of both depression and anxiety based on self-reported screening instruments and used different cut-off scores to examine symptom severity. Notably, two internationally validated mental health scales were used as well as statements providing more in-depth insight into pregnant and postpartum women’s experiences.To our knowledge, this study is the first to give an overview of the perinatal mental health status during the third wave of the pandemic in a uniform manner across several European countries.
In addition to its strengths, this study also has several limitations, some of which are inherent to all online surveys. First, a conventional response rate calculation is not possible in anonymous online surveys. Therefore, we must rely on indirect measures, that is, a comparison with national birthing population data, to assess the study’s external validity (online supplemental table 2). Second, we observed demographic biases in participation with an under-representation of women from the Netherlands, Switzerland and the UK. Although our sample represents women of childbearing age, the study included more women with prior children, this may have affected study representativeness and limited the generalisability. Participants were more highly educated and professionally active than national birthing population data. This finding might indicate a selection bias towards more healthy study participants. Hence, the possibility that the more severely depressed or anxious women were either under-represented or over-represented in the online survey cannot be excluded. This may also explain the somewhat lower prevalence rates of depression and anxiety in this study population compared with the meta-analysis results.5 Therefore, our results may not be fully representative of the target birthing population in the selected countries. We did not apply survey weights to take account of unequal sample selection, as demographic characteristics such as age and education specifically in pregnant or postpartum women are not readily available in all countries for generating these weights. This could affect the variance of some covariates; it also means that the population included in the analysis does not reflect a representative sample of the countries and might preclude the generalisability of results. Lastly, the cross-sectional design limited our capacity to determine the temporal sequence between mental health and associated factors; however, some factors, for example, chronic conditions, occurred before measuring current mental health status.
Implication for practice
The results from this European cross-sectional study form a basis for further prospective studies on socioeconomic, clinical, reproductive and environmental determinants of mental health among perinatal populations during times of pandemics. The results underscore the importance of healthcare providers to be observant of mental health symptoms among pregnant and postpartum women in their care, especially during pandemics.
Conclusion
Approximately one in six pregnant and postpartum women in five European countries reported symptoms of major depression and anxiety during the third wave of the pandemic. This suggests a continued need to monitor depression and anxiety in pregnancy and postpartum populations throughout the pandemic. Tailored support and counselling are essential to reduce the burden of the pandemic on perinatal and infant mental health.
Data availability statement
All data relevant to the study are included in the article or uploaded as online supplemental information. Researchers can apply for data access for subprojects within the overall aims of the main study.
Ethics statements
Patient consent for publication
Ethics approval
Electronic informed consent was obtained from the participants before the survey. Ethical approval was waived in Norway, Switzerland, The Netherlands, and the UK as data were anonymously collected. In Belgium, ethical approval was obtained from the Ethics Committee Research UZ/KU Leuven (S63966; May 26th, 2021). All data were stored and handled anonymously.
Acknowledgments
The authors are grateful to the following individuals for their help with this study: Jonathan Luke Richardson (The UK), Elias Refstie (Norway), Leo Pomar (Switzerland), Gerda Weits (The Netherlands), PriyaSomar (The Netherlands), SaskiaVorstenbosch (The Netherlands), Loes de Vries (The Netherlands), CarlijnLitjens (The Netherlands), Ursula Winterfeld (Switzerland), Milos Stojanov (Switzerland). We thank Susan Garthus-Niegel and Malin Eberhard-Gran for use of the questions regarding anxiety following COVID-19-related changes in this survey. We would also like to thank all who helped us advertise our study.
References
Supplementary materials
Supplementary Data
This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.
Footnotes
Twitter @Pharma_Nordeng
Contributors FT, HN and AL designed the study with input from MC, EG, AP, AO, VF and AP. FT analysed the data with support from HN and AL. FT, HN and AL wrote the manuscript with input from MC, EG, AP, AO, VF and AP. All authors contributed to interpreting the results and critically revised the manuscript. Finally, all authors read and approved the final manuscript. FT is responsible for the overall content as the guarantor.
Funding The study did not receive funding. The research activities of MC were supported by the Faculty of Pharmaceutical Sciences and the Department of Pharmaceutical and Pharmacological Sciences (KU Leuven). HN was supported by the Norwegian Research Council EU-COVID-19 (grant no. 312707).
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.