The prevalence of polycystic ovarian syndrome in Chinese women: a meta-analysis

Introduction

Polycystic ovarian syndrome (PCOS) is the most common gynecological, endocrine system disease among women aged 18 to 44 (1). Its key characteristics are persistent anovulation, hyperandrogenism, and insulin resistance. The main manifestations are menstrual disorders and reproductive dysfunction (2-4), one of the leading causes of females in anovulatory infertility (5,6). The World Health Organization estimates PCOS has affected over 116 million women worldwide as of 2010 (7). The incidence of long-term complications, including cardio-cerebrovascular diseases, hypertension, lipid metabolism disorders, and endometrial cancer in patients with PCOS, is 2 to 6 times ordinary people (2). At present, the etiology of PCOS is still unclear. Most scholars believe it may be related to the abnormal regulation function of the hypothalamic-pituitary-ovarian axis, hyperinsulinemia and insulin resistance, abnormal adrenal endocrine function, heredity, and other aspects (8,9). For decades, because of the differences in diagnostic criteria, sampling methods, and the gradual maturity of diagnosis and treatment techniques, the prevalence rates were retrieved by domestic and foreign scholars in the epidemiological investigations on PCOS vary greatly. Previous studies have reported that the prevalence rate of PCOS among women of childbearing age in various countries is between 5% and 10% (10). In recent years, large-scale investigations of PCOS have been carried out in different regions of China (11-13). However, due to the lack of a comprehensive data collection and analysis system, there is still no data on the exact frequency, distribution pattern and trend of PCOS nationwide. This study used the research method of meta-analysis to review the latest evidence systematically from the regional population survey of PCOS to understand the prevalence of PCOS in different regions and different populations fully, thus contributing to its control and management. We present the following article in accordance with the PRISMA reporting checklist (available at http://dx.doi.org/10.21037/apm-20-1893).

Methods

Search strategy

This study will be conducted according to PRISMA guidelines. Eight databases including China National Knowledge Infrastructure, Wanfang Data, China Science and Technology Journal Database, Chinese Biology Medicine, PubMed, Embase, The Cochrane Library and Web of Science were searched to collect studies on the prevalence of PCOS in Chinese women from setting up a database to May 31, 2020. To increase the sensitivity, we use a combination of subject heading terms and free text words to retrieve documents. The subject headings include: “polycystic ovarian syndrome” and “prevalence” or “incidence” or “epidemiology” and “China” or “Chinese.” The free words include: “The People’s Republic of China” or “Mainland China” “Formosa” and “Stein-Leventhal Syndrome” or “Sclerocystic Ovarian Degeneration” or “Sclerocystic Ovary” and “occurrence” or “outbreaks” or “prevalence” or “endemics” or “incidence”.

Inclusion and exclusion criteria

The inclusion criteria are: (I) type of study: prospective or retrospective studies on the prevalence of PCOS in Chinese women published at home and abroad; (II) study population: Chinese women with a definite diagnosis of PCOS; (III) outcome indicators and the prevalence of PCOS.

The criteria for exclusion were: (I) studies with incomplete information and data that cannot be extracted; (II) studies reported or published repeatedly in the same research population, excluding those of lower quality; (III) studies not in Chinese or English; (IV) study where only the abstract is visible, and the full text cannot be obtained by contacting the author; (V) studies with low quality (the AHRQ score is below 3).

Data extraction

Two investigators (Q Wu, Z Yang) independently screened the literature, extracted data, and cross-checked. If the two researchers have inconsistent conclusions, then through discussion to resolve differences. If the differences cannot be resolved, the third party will perform judgments and arbitration. First, read the title and abstract, and after excluding irrelevant studies, read the full text further to determine whether it will be included. The content of the data extraction includes the first author, publication year, study design, research area, age, number of PCOS cases and sample size, occupation, education background, diagnostic criteria.

Statistical analysis

STATA (version 15.1; Stata Corporation) software was used to conduct statistical analysis and the point prevalence rates were first transformed into arcsine square-root transformed proportions (14). The heterogeneity between the included studies was determined by the Q test (P value) and I². If I²<50% and P>0.1 of the Q test, it is considered the homogeneity between the studies is satisfactory, the fixed-effect model is used for meta-analysis. On the contrary (P≤0.1 or I²≥50%), it is considered there is evident heterogeneity among studies, and the random effects model is used for combined calculation. A subgroup analysis was performed to explore the possible sources of heterogeneity among studies. Also, the subgroup analysis was conducted according to different regions, occupation/identity, age, publication time, diagnostic criteria, survey time, and survey population. Begg’s test and Egger’s test were used for conducting a publication bias assessment. It is considered statistically significant when P<0.05. In addition, a sensitivity analysis was performed to measure the impact of any research on aggregate estimates.

Quality assessment

The quality of the included studies was tested using the cross-sectional study quality evaluation standards recommended by the Agency for Healthcare Research and Quality (AHRQ). The AHRQ (15) standard contains 11 items, which are answered with “yes”, “no,” and “do not know”, respectively. If the answer is “yes”, the item is judged as “1”, “no” or “no.” “Clear” is “0” points. The score ranges from 0 to 11 points, 0 to 3 are low quality, 4 to 7 are medium quality, and 8 to 11 are of high quality. The literature quality evaluation was conducted independently by two researchers (Qiao Wu and Qin Liao), and the results were cross-checked. If the conclusions of the two researchers were inconsistent, a consensus was reached through discussion.

Results

Study selection and participants characteristics

The literature screening process and results are shown in Figure 1. A total of 5,576 papers were obtained from the preliminary search, among which 265 were from PubMed database, 108 from Embase, 708 from Web of Science, CENTRAL 33, CNKI 1,071, WanFang Data 1,479, VIP 667 and CBM 1,345. After reading the title, abstract and eliminating duplicate studies, a total of 4,409 articles were excluded. Then after further reading the full text, according to the literature inclusion and exclusion criteria, 62 documents whose data could not be extracted were excluded, 15 documents whose document type was review, 29 articles with a quality score of less than 3, and 21 documents with duplicate data, 17 documents without a clear survey location, 69 articles were finally included papers on PCOS prevalence in Chinese women (65 in Chinese and 4 in English). A total of 154,599 patients were enrolled, including 12,845 patients with PCOS. The literature includes 23 provinces (cities, autonomous regions, and particular administrative regions), including 15 Midwestern Sectional Figure Skating Championships, 33 in the Eastern Region, 16 in the central region, and 4 in the northeast. Among them, three were of low quality, and 57 were of medium quality, and five were of high quality. The primary characteristics of the included studies are shown in Table 1.

Figure 1 The flow diagram of this meta-analysis.

Table 1 The basic characteristics of the included studies
Full table

Pooled prevalence rates of PCOS

Sixty-nine articles, including 154,112 subjects and 12,845 patients, were included. The prevalence rate of PCOS reported in each study ranged from 0.45% to 35.14%. A heterogeneity test was performed on the included 69 articles, and there was significant heterogeneity among the articles (I²=99.6%, P<0.05), so the random effects model was adopted. From the fact that there are more ratios in this study between 0–0.3 and 0.7–1, the double arcsine conversion method was used to convert the rates and then combine to calculate the prevalence. The combined conversion rate from the random effects model was 0.64 (95% CI: 0.58–0.70), and the total prevalence of PCOS in Chinese women was 10.01% (95% CI: 8.31–11.89%) (Figure 2).

Figure 2 Forest plots of the total prevalence of polycystic ovary syndrome in Chinese women.

Subgroup analysis

Subgroup analysis was conducted by region, occupation/identity, age, time of publication, diagnostic criteria, and survey population. The study area is divided into eastern, northeastern, central, and western regions, according to China’s four economic zones. Occupations/identities are divided into workers, students, medical personnel, cadres, farmers, clerks, and service personnel. The age is divided into 10–20, 21–30, 31–40 years old, and over 40 years old. Research sites are divided into hospitals, communities, and schools. The year of publication is in a period of every five years. Subgroup analysis results are shown in Table 2.

Table 2 Subgroup analysis of the prevalence of polycystic ovary syndrome in Chinese women
Full table

Sensitivity analysis and publication bias

Sensitivity analysis showed there was no significant difference between the results obtained and the total combined estimate when each of the included articles was excluded one by one, showing that the results were stable. Funnel chart and Begg’s method and Egger funnel figure asymmetric inspections method analysis were performed. The results show Begg’s rank correlation test income =0.81, P=0.41, and Z suggests no publication bias, and P=0.01 Egger regression analysis income. Further, the funnel chart shows apparent asymmetry, suggesting a potential publication bias, language bias, the small-scale flawed method in the study designed to estimate highly. Therefore, the effect of publication bias on the results was tested by the shear compensation method. The results showed that the estimated value of the combined effect size did not change significantly, suggesting that publication bias had little impact on the results, and the meta-analysis results were relatively stable (Figures 3,4).

Figure 3 The funnel plot diagram of Beggar rank correlation analysis

Figure 4 The funnel diagram of the shear compensation method.

Discussion

PCOS is the most common endocrine disease in women of childbearing age, and its clinical manifestations are highly heterogeneous (82), which can be easily confused with endocrine diseases, including hyperprolactinemia, abnormal thyroid function, and congenital adrenal hyperplasia (83). So far, there is no cure for PCOS, but the related health risks are lifelong. Even after menopause, women with PCOS still often have higher levels of androgen and insulin resistance (3,9). In recent years, the incidence of PCOS has all increased (84), and with the improvement of diagnostic methods and the level of diagnosis and treatment, its prevalence may change accordingly. Therefore, this study intends to assess the prevalence of PCOS in Chinese adult women and analyze the time tend to determine the current prevalence of PCOS in Chinese women to decide for the prevention and treatment of PCOS to provide evidence.

Sixty-nine articles published from 1985 to 2019 were included in this study and described the prevalence of PCOS among Chinese women through the method of meta-analysis. The results show the total prevalence of PCOS in China is 10.01%, which is higher than the results obtained by Rong Li (11) and others in the epidemiological survey of female PCOS in 10 provinces (cities). However, the prevalence of PCOS in this study was lower than that in Middle Eastern women (16%) (85), which may be related to race, region, economic and cultural level, and the improvement of PCOS knowledge and diagnosis.

The study also found significant differences among regions, occupation/identity, age, time of publication, diagnostic criteria, and prevalence rates among survey populations. In terms of regional differences in the prevalence rate of female PCOS, the prevalence rate of female PCOS in eastern regions is significantly lower than that in central and western regions, which might be because of the following reasons: (I) compared with the eastern region, the economic status of the central and western regions is slightly lagging. The socioeconomic status of women is low. Relevant studies have shown that low socioeconomic status is related to increased exposure to environmental BPA (86), and this synthetic compound may be related to PCOS (87). Relevant animal studies have shown (88) that there is an association between the development of PCOS symptoms and exposure to BPA during the newborn period. Simultaneously, women in the central and western regions are insufficient preventive and health care conditions because of the lagging economic status (89), which delays the treatment of PCOS. (II) It is related to the living environment between regions. Women in the central and western regions are more likely to be in backward agricultural areas than women in the eastern regions and are more likely to be exposed to environmental toxins, including pesticides and smog. Studies have shown that environmental toxins have a significant impact on human health. Pollutants, including smoke, lead, pesticides, and mercury, may damage women’s reproductive health and may trigger or aggravate PCOS and its related symptoms (90).

In terms of the difference in the prevalence of PCOS between different occupations/identities: PCOS has the highest prevalence among students. The reasons may be because of: (I) students have prolonged mental work hours and high intensity, and their bodies are under long-term stress. Catecholamine increased secretion causes the body’s endocrine function disorder, sympathetic nerve excitability, and hypothalamus-pituitary-adrenal cortex hormone secretion increases, thereby reducing immune function. These factors may accelerate the occurrence of PCOS (91). (II) Students often have lousy living habits, including reversed work and rest and irregular eating and less exercise and exercise, and these are all predisposing factors for PCOS (92). As a group of people with higher socioeconomic status, cadres have better medical and health conditions and pay more attention to their health conditions, have a relatively healthier lifestyle, and reduce the chance of PCOS.

The results of a subgroup analysis with age in this study showed that the prevalence rate was 10.26% for 10 to 20 years old, 17.23% for women aged 21 to 30, and 9.13% for women aged 31 to 40, >40 years old. The prevalence of PCOS in women was 2.22%. This result shows that the prevalence of PCOS decreased significantly with age from 21 to 30 years old, suggesting that age may be related to PCOS. The reason might be because of the prosperous childbearing period for women of childbearing age between 20 and 29 years old, female reproductive endocrine function reaches its peak state, the ovarian endocrine function is vigorous, and women’s ovarian endocrine function enters a state of gradual decline around 40 years old (93). The prevalence of PCOS, which is closely related to endocrine function, also decreases with the gradual weakening of ovarian endocrine function.

In terms of publication time, from 2001 to 2015, the prevalence of female PCOS has shown an upward trend. The reason may be that with the development of economy and medical and health conditions, increased patients with PCOS-related symptoms tend to go to the hospital for treatment. Also, with the improvement of diagnosis and treatment methods, and the gradual improvement of PCOS diagnostic criteria, the diagnosis rate of PCOS has increased. The prevalence of PCOS has declined since 2016. The decline might be related to the changes in the age structure of the population in the country. The number of women of childbearing age in this study’s country has shown a decreasing trend year by year. According to the 2018 Government Work Report, there were 4 million fewer women of childbearing age-aged 15 to 49 in 2017 than in 2016, with nearly 6 million fewer women of childbearing age-aged 20 to 29 during their fertile years.

Comparing the prevalence of women using the diagnostic criteria of the National Institutes of Health in 1990, the Rotterdam criteria in 2003 and the PCOS diagnostic criteria developed by the American Androgen Association in 2006, the prevalence of PCOS diagnosed using the Rotterdam criteria in 2003 is significant It is higher than the other two is like the results of researchers including Anahita Jalilian (10). However, some studies believe the Rotterdam criteria may include some women with mild phenotypes into the diagnosis, increasing the incidence of PCOS (94). In terms of the prevalence of PCOS in different survey sites, the survey conducted in the hospital has a higher prevalence rate, while the survey conducted in the school has a lower prevalence rate. The reason might be because of the differences in the subjects of the survey. Most surveys conducted in the hospital were women who had symptoms related to PCOS and went to the hospital for treatment. The cases were concentrated. The low prevalence of the survey conducted in schools may be related to insufficient self-health care, awareness of students, insufficient relevant knowledge of PCOS, and insufficient school medical and health conditions. When students have PCOS-related symptoms, including irregular menstruation and acne, they are often overlooked and miss the diagnosis and treatment of the disease.

This study also has certain limitations. Firstly, it is limited by the characteristics of single rate meta-analysis, and the heterogeneity between the literature is considerable. Secondly, significant heterogeneity exists among different studies. Although inclusion and exclusion criteria are strictly limited and subgroup analysis is conducted, the results cannot fully explain the source of heterogeneity, and unknown sources of heterogeneity may cause certain bias. Finally, only 69 studies covering 23 provinces in China were included in this study. The results were not enough to reflect the prevalence and characteristics of PCOS in all Chinese women.

Conclusions

To sum up, PCOS has a high prevalence rate in Chinese women, a significant public health problem in China. Therefore, medical and health departments should pay more attention to this situation. According to the research results, the disease has a high prevalence rate in the central region, students, and women aged 21 to 30. Therefore, more targeted screening measures should be adopted for people with the characteristics of this population, and tertiary prevention of PCOS should be actively carried out, to make an early diagnosis and early treatment, and reduce relevant medical and health resources.

Acknowledgments

Funding: None.

Footnote

Reporting Checklist: The authors have completed the PRISMA reporting checklist. Available at http://dx.doi.org/10.21037/apm-20-1893

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at http://dx.doi.org/10.21037/apm-20-1893). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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