Evaluating the global prevalence of insomnia during pregnancy through standardized questionnaires and diagnostic criteria: a systematic review and meta-analysis

Introduction Insomnia during pregnancy presents significant medical care challenges and heightens the risk of adverse outcomes for both pregnant women and fetuses. This study undertook a meta-analysis to assess the global prevalence of insomnia during pregnancy, examining both the overall prevalence and regional variations. Method The aim of this study was to perform a meta-analysis of articles indexed in PubMed, Embase, and Web of Science from the inception of these databases up to February 29, 2024. The study systematically reviewed the global prevalence of gestational insomnia and explored potential moderating factors, encompassing research type, publication date, regional influences, maternal age, pregnancy status, depressive symptoms, and anxiety symptoms. Result Forty-four studies, encompassing a total of 47,399,513 participants, were included in the analysis. The overall prevalence of insomnia symptoms during pregnancy was 43.9%. Regional factors and depression emerged as the main factors affecting insomnia, with Europe (53.6%) surpassing North America (41.0%), followed by South America (50.6%) and Asia (40.7%). High depression rates (56.2%) correlated with increased insomnia prevalence compared to low depression rates (39.8%). The type of research and publication date showed no significant impact on the prevalence of insomnia symptoms. Conclusion The meta-analysis results indicated that the prevalence of insomnia symptoms was higher during pregnancy, especially among pregnant women who were in a highly depressed state or located in the European region. Systematic review registration PROSPERO, identifier CRD42018104460.


Introduction
Insomnia is a common clinical disorder characterized by difficulty falling asleep or maintaining sleep, often accompanied by symptoms such as irritability or fatigue when awake.It often occurs at least three times a week and lasted for a duration of at least three months, and can't be attributed to other diseases or substances (1).
Research indicates that the incidence rate of insomnia in adults typically ranges from 6% to 10%, whereas among pregnant women it is notably higher at 38.2% (2,3).Insomnia during pregnancy can be attributed to a varied of factors, such as physical discomfort, hormonal fluctuations, fetal growth (4), and emotional distress.Research has shown that insomnia during pregnancy (5) not only leads to a decline in quality of life, but also is a potential cause of premature delivery, cesarean section, prolonged delivery, pregnancy induced hypertension, pregnancy induced diabetes, and postpartum depression.Lu conducted a comprehensive review of sleep disorders and their association with adverse maternal and infant outcomes.The results revealed that sleep disorders, including insomnia, were associated with an increased risk of adverse pregnancy outcomes such as preeclampsia (OR=2.80,95% CI 2.38-3.30),hypertension during pregnancy (OR=1.74,95% CI 1.54-1.97),diabetes during pregnancy (OR=1.59,95% CI 1.45-1.76),cesarean section (OR=1.47,95% CI 1.31-1.64),and premature delivery (OR=1.38,95% CI 1.26-1.51)(6); Additionally, a study demonstrated that insomnia was associated with an increased risk of perinatal suicide (OR=4.76,95% CI 1.83-12.34)(7).Therefore, insomnia poses a significant threat to maternal and fetal health throughout pregnancy.
In the 2020 review on the prevalence of insomnia, the authors conducted subgroup analysis on variables including maternal age, gestational age, depressive symptoms, and gestational period (8).The review found that maternal age, gestational age, and anxiety significantly impact the prevalence of insomnia.Due to the limited number of articles included, the authors did not compare regional prevalence rates.As is well known, insomnia during pregnancy is a sleep disorder caused by various confounding factors.Regional studies are important for the prevention of women's health.In China, a cross-sectional study on insomnia in Chinese pregnant women showed that 24.3% of the pregnant women suffered from insomnia, and found that maternal age, attained education, occupation, monthly household income, insurance coverage, relationship with the mother-in-law, gestational age, and anxiety symptoms were independently risk factors for insomnia (9).A Canadian study found that good social attention and partnership can reduce the incidence of prenatal depression and thus reduce the risk of insomnia during pregnancy (10).Similarly, several studies of pregnancy insomnia in the United States have found that degree of social concern is related to differences in the risk of pregnancy insomnia (11,12).What's more, different countries and regions may also have significant differences in the prevalence of insomnia during pregnancy due to diet, social life pressure, cultural background, and national women's policies.
Based on this, we conducted a comprehensive database search and compare the prevalence of insomnia during pregnancy in different countries by region.These results will provide some reference evidence for the formulation of prevention and health policies in high prevalence areas, thereby increasing social attention to women's health.

Methods
A systematic review and meta-analysis were conducted on articles related to insomnia symptoms during pregnancy.Both systematic reviews and meta-analyses were reported in accordance with the PRISMA Declaration Guidelines (13).This review has been registered in the PROSPERO database (registration number: CRD42018104460).The PRISMA checklist could be found in Supplementary Material 1.The PICOS method was used in formulating research questions (14).

Search strategy
A full-text search was conducted on the PubMed, Embase, and Web of Science databases, with a time limit for papers published until February 29, 2024, including articles that reported insomnia rates during pregnancy through self-report or questionnaire surveys.The search algorithm was based on terms such as 'pregnancy' and 'insomnia'.Specific search strategies were in Supplementary Material 2.
The selected titles and relevant abstracts of the articles were reviewed.Each article was categorized as 'yes', 'no', or 'possible', with articles marked as 'no' being excluded from the analysis.The entire articles with titles or abstracts marked as 'yes' or 'possible' were thoroughly reviewed to determine if they met the inclusion criteria.Please refer to Figure 1 for a detailed flowchart outlining the detection program for the study.

Research selection
The P-population was Women with pregnancy, the I-study has no intervention, the C-compare with and without sleep problem, the O-outcome is insomnia, and S-study included Randomized controlled studies, cohort studies, cross-sectional studies, casecontrol studies.The study included data on the prevalence of insomnia among pregnant women, or reported the number of individuals with insomnia.Research methods involved self-reporting, questionnaire surveys, and the measurement of epidemiological data.
Exclusion criteria: The sample consisted solely of pregnant women with sleep disorders.Studies that used non-standardized measurement methods, such as evaluating insomnia with a single question, were not included.Furthermore, studies that were case reports, systematic reviews, or used data from previous studies were also excluded.
The first and second authors (FR and WH) independently reviewed these studies and conducted a full-text review based on inclusion and exclusion criteria to further exclude studies that were not qualified.Any differences were be resolved by the senior author (ZS).

Data extraction
The first (FR) and second (WH) authors independently extracted data to confirm accuracy.The third author (ZS) confirmed the accuracy of the included data.The studies selected for review are recorded using standardized tables to describe the important variables of each study.The estimated prevalence of insomnia was obtained by extracting data on the number of cases, total sample size, or percentage of samples identified as having insomnia symptoms, as well as the study type, region, maternal age (year), gestational age (week), and percentage of anxiety or depression cases (see Table 1).
Meta-analysis was conducted using the comprehensive software STATA 16.0.A random effects model was chosen for analysis based on the level of heterogeneity, typically with I 2 >50%.The I 2 index was used to assess heterogeneity between point estimates, indicating the proportion of variation between point estimates attributed to heterogeneity.Traditionally, I 2 values below 25% suggest low heterogeneity, while values between 25% and 50% suggest moderate heterogeneity, and values above 50% suggest high heterogeneity.Subgroup comparison was then employed to further investigate the sources of heterogeneity.

Quality evaluation
The Newcastle-Ottawa Scale (NOS) was used to evaluate the quality of the included observational studies, and it was generally considered that 1-3 was classified as low quality, 4-6 as medium  quality, and 7-9 as high quality.Randomized controlled trials were evaluated using the Cochrane risk bias assessment tool.
Figures 2 and 3 displayed a summary of insomnia prevalence rates and subgroup forest plots, indicating an estimated range of 1% -77.1% for the prevalence of insomnia among 44 study patients.The overall prevalence rate was 43.9% (33.5% -54.4%).On this basis, multiple subgroup analyses were conducted.

FIGURE 2
Analysis results of total prevalence of insomnia.

Subgroup analysis based on psychological depression participants
Based on classification analysis, it was discovered that in studies with a high prevalence of depression, the occurrence of gestational insomnia rose by 56.2% (49.8% -62.6%).This indicates that depression is a contributing factor to the elevated rates of insomnia.

Quality evaluation
The overall quality of the included literature was deemed high, with 24 studies in Table 2 offering moderate evidence and 2 studies presenting low-level evidence.Only one article in the randomized controlled study indicated low quality, as shown in Figure 4.The high quality of the papers contributes to the reliability of the analysis results.

Sensitivity analysis
After deleting each study item by item (Figure 5), the overall estimates remained stable, indicating that the studies did not significantly affect the overall combined prevalence estimate.

Discussion
An in-depth analysis was conducted on the various factors influencing insomnia during pregnancy, indicating that sleep quality can be significantly impacted by pregnancy.As the pregnancy advances, there is a noticeable decline in sleep quality, with late pregnancy being the most disruptive period (53).Studies have indicated a strong correlation between subjective sleep scores and the severity of depressive symptoms (55).Moreover, pregnancy represents a physiological state characterized by continuous hormonal, physical, and behavioral changes that may significantly alter both sleep quality and duration (56).Overall prevalence and subgroup analysis of insomnia.The study found that the total prevalence of insomnia during pregnancy was 44.0%, significantly higher than the general population.This highlights the importance of addressing insomnia as a significant health issue during pregnancy.Subgroup analysis by region revealed the highest prevalence in Europe and the lowest in Asia.Further analysis was then conducted at the country level.
Among European countries, Spain, Poland, and Norway exhibited a higher risk of insomnia compared to the overall level of insomnia in this analysis.This finding is in line with previous European studies that have shown a relatively high prevalence of insomnia in the European population (57,58).Pregnancy events will further exacerbate the burden of female insomnia.A selfreported survey conducted by David O'Regan on individuals with insomnia in Europe identified lifestyle factors and high levels of life stress as the primary causes of insomnia (59).Numerous articles on insomnia have also highlighted the impact of lifestyle factors such as diet, exercise, smoking, and sleep habits on the development of insomnia (60).Additionally, a study on diet and insomnia revealed a positive association between dietary glycemic load and insomnia risk (OR: 1.10; 95% CI, 1.01, 1.20) (61).Spain, Poland, and Norway, being developed countries, often experience higher life burdens and pressures due to the pursuit of a high quality of life.Meanwhile, the preference for sugary foods among Europeans may contribute to the increased risk of insomnia (62)(63)(64).
In the Asian subgroup analysis, Japan, a developed country, exhibited a higher prevalence of insomnia during pregnancy, in line with expectations.The study revealed that, apart from economic pressures, the societal focus on women played a significant role in causing insomnia.Notably, China has specific support measures for pregnant women, including reduced working hours, dietary adjustments, and tailored psychological counseling, effectively alleviating psychological stress (65,66).Moreover, within the Chinese cultural context, pregnant women receive extensive care from family members, contributing to a low insomnia rate (65).These findings offer valuable insights for designing women's health initiatives.Conversely, the status of women in Japan is comparatively lower, hindering access to social support and contributing to the high prevalence of insomnia among pregnant women (67).
North America mainly includes the United States and Canada.In this analysis, only the United States was considered, revealing a lower insomnia rate compared to the overall level.Throughout the past century, the United States has dedicated efforts to safeguarding women's power and status.Additionally, being the most developed country globally, the United States boasts top-tier economic and medical advancements.These factors, including a robust system and favorable economic and medical conditions, play a vital role in ensuring a safe pregnancy and reducing the risk of insomnia in pregnant women (68)(69)(70).
A correlation between insomnia and depression has been observed.In recent years, the detection rate of pregnancy complications in clinical practice has been on the rise (71), attributed to changes in the living environment, maternal neuroendocrine function, and abnormal fetal development.Studies both domestically and internationally have reported a prevalence rate of depression symptoms during pregnancy among women with pregnancy complications ranging from 29.4% to 39%, significantly surpassing that of healthy pregnant women (72,73).
Through data analysis, it was found that individuals with high levels of depression were at a higher risk of insomnia, and depression was positively correlated with an increase in sleep latency.A study found differences in the consistency of local activity in the auxiliary motor area and insula between patients with insomnia and those without.Patients with insomnia and severe depression exhibited differences in the intensity of spontaneous activity in the middle frontal gyrus and paracentral lobules compared to those without insomnia.Previous studies have shown that the potential neurobiological mechanisms of depression and insomnia symptoms may have included: (1) abnormalities in monoamine neurotransmitters, especially changes in 5-HT concentration, which were closely related to sleep awakening and depression, such as shortened REM latency in patients with depression; (2) Overexpression of biological clock genes and stress response genes; (3) Dysfunction of the hypothalamic pituitary adrenal axis (HPA) and abnormal release of cortisol (74).According to data, there was a close relationship between insomnia during pregnancy and depression at both the symptom and disease levels.Some women's insomnia symptoms were relatively stable in the early stages of pregnancy, but temporarily increased in the late stages of pregnancy.This is closely associated with significant physiological and psychological changes, and pregnancy can be characterized as a period of heightened biological and situational stress (75), which may activate latent vulnerabilities and magnify them.Hence, many pregnant women might experience a worsening of insomnia symptoms in the later stages of pregnancy.For instance, around 70% of individuals with depression experience symptoms of insomnia, and the prevalence of depression among pregnant women with insomnia is 3-4 times higher than in those without insomnia (76).This bidirectional and cumulative relationship necessitates greater clinical attention, as gestational insomnia and depression both pose risk factors for adverse pregnancy outcomes.Insomnia during pregnancy is not inherently harmful, but it can contribute to an elevated risk of various health complications for women, such as stillbirth, miscarriage, perinatal depression, and other adverse outcomes.As a result, it is essential to focus on nonpharmacological methods for preventing and managing insomnia during pregnancy.Psychological and social factors play a significant role in the varying prevalence of insomnia during pregnancy, with psychological factors often being linked to some social factors.Pan Chen and Eric S Kim suggest that enhancing overall well-being can be an effective way to alleviate negative psychological symptoms (77,78).Therefore, enhancing the focus on women during pregnancy is crucial for safeguarding their health (79).China, with its historical cultural background, has shown a greater emphasis on women's health compared to other developed countries.Drawing from China's approach, strategies such as reducing the work intensity of pregnant women, promoting increased attention from family members and social groups, providing regular psychological counseling, and encouraging appropriate exercise like relaxation training and mindfulness can help alleviate psychological issues during pregnancy and improve sleep quality to some extent (80).

Limitations
In this meta-analysis, significant heterogeneity was found, which may be attributed to population characteristics, study design, evaluation of insomnia and measurement of outcomes, as well as clinical stages of pregnancy.Secondly, insomnia mainly came from subjective reports or questionnaire surveys, and differences in diagnosis may have a certain impact on the results.Due to the fact that the summary result of single arm rate is a descriptive result and not a difference comparison result, the statistical significance of publication bias is not strong.We strictly followed the inclusion and exclusion criteria to manually screen relevant articles, without any restrictions on the language or year of the study, thus minimizing the possibility of omitting any research related to the topic; We also conducted a stratified analysis based on geographical location, publication time, literature type, and degree of depression.Therefore, compared to other small-scale studies, our research results may have more reference value and robustness.Finally, due to the limited data on insomnia across various gestational periods, a subgroup analysis based on these different periods has not yet been conducted.Further studies are anticipated to provide additional verification in the future.

Conclusion
The prevalence of insomnia during pregnancy, reaching as high as 44%, has been displaying an upward trend year by year.Urgent attention must be directed toward women's health issues.Insomnia during pregnancy not only elevates the risk of adverse pregnancy outcomes for women but also significantly affects fetal development and postpartum well-being.As widely acknowledged, insomnia during pregnancy stems from various complex factors, with regional disparities emerging as a central aspect warranting special attention.We aim to undertake further regional research in the future to enhance clinical evidence for developing regional policies aimed at safeguarding women's health.

FIGURE 4
FIGURE 4Quality evaluation of 4 randomized controlled trials included.

TABLE 1
Basic information included in the literature.

TABLE 2
The NOS scales evaluation table for observational studies was included.