|Year : 2022 | Volume
| Issue : 1 | Page : 26
Menstrual and reproductive factors and risk of breast cancer in iranian female population: A systematic review and meta-analysis
Elham Manouchehri1, Ali Taghipour2, Vahid Ghavami3, Fatemeh Homaei Shandiz4, Abbas Ebadi5, Robab Latifnejad Roudsari6
1 Department of Midwifery, School of Nursing & Midwifery, Mashhad University of Medical Sciences, Mashhad, Iran
2 Department of Epidemiology, School of Public Health, Mashhad University of Medical Sciences, Mashhad, Iran
3 Department of Biostatistics, School of Health, Mashhad University of Medical Sciences; Social Determinants of Health Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
4 Cancer Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
5 Behavioral Sciences Research Center, Life style institute, Baqiyatallah University of Medical Sciences; Nursing Faculty, Baqiyatallah University of Medical Sciences, Tehran, Iran
6 Department of Midwifery, School of Nursing & Midwifery, Mashhad University of Medical Sciences; Nursing and Midwifery Care Research Center, Mashhad University of Medical Sciences, Mashhad, Iran
|Date of Submission||22-Oct-2020|
|Date of Acceptance||15-May-2021|
|Date of Web Publication||23-Feb-2022|
Robab Latifnejad Roudsari
Department of Midwifery, School of Nursing and Midwifery, Mashhad University of Medical Sciences, Mashhad
Source of Support: None, Conflict of Interest: None
Background: Breast cancer (BC) is the most frequent cancer in Iranian females. Due to the changes in lifestyle and reproductive risk factors, the BC incidence rate has been rapidly increasing. Knowing risk factors of BC could significantly contribute to improve preventive behaviors. To investigate the relationship between menstrual and reproductive factors and BC in Iranian female population. Methods: Web of Science, PubMed, Scopus, and SID as well as references of included studies were searched. Among relevant published observational studies, 27 studies met the inclusion criteria. Pooled risk estimates for the risk factors were determined using random-effects models due to the presence of substantial heterogeneity (P < 0.05). Results: All of the selected studies had case–control design. There was a positive relationship between maternal age at first pregnancy and risk of BC (OR = 1.79 95% CI: 1.36–2.35). Also, menopausal status was associated with higher risk of BC (OR = 1.60 95% CI: 1.18–2.17), whereas, there was no association between menarche age and increased risk of BC (OR = 0.55 95% CI: 0.29–1.03). History of abortion (OR = 1.21 95% CI: 0.97–1.5), nulliparity (OR = 1.43 95% CI: 0.89–2.31), and breastfeeding history (OR = 0.68 95% CI: 0.42–1.09) were not associated with BC risk. Conclusions: Our findings suggest that age at the first pregnancy and menopausal status were significantly associated with BC risk among Iranian women, whereas menarche age, nulliparity, and history of breastfeeding were not. In regard to the history of abortion, our findings revealed no association with BC, but in high-quality studies, this relationship was significant.
Keywords: Abortion (induced, spontaneous), breast neoplasm, breastfeeding, menopause, reproductive history
|How to cite this article:|
Manouchehri E, Taghipour A, Ghavami V, Shandiz FH, Ebadi A, Roudsari RL. Menstrual and reproductive factors and risk of breast cancer in iranian female population: A systematic review and meta-analysis. Int J Prev Med 2022;13:26
|How to cite this URL:|
Manouchehri E, Taghipour A, Ghavami V, Shandiz FH, Ebadi A, Roudsari RL. Menstrual and reproductive factors and risk of breast cancer in iranian female population: A systematic review and meta-analysis. Int J Prev Med [serial online] 2022 [cited 2022 May 24];13:26. Available from: https://www.ijpvmjournal.net/text.asp?2022/13/1/26/338086
| Introduction|| |
Breast cancer (BC) is one of the most serious health problems among women worldwide. BC is also the most common cancer in Iranian female population and its incidence rate has doubled throughout three past decades. BC is a multifactorial disease and various factors are involved in its development. It is notable that not all women have the same risk of BC throughout their lives, but specific risk factors could increase their chances to experience the disease. The role of reproductive factors such as menarche age, age at first childbirth, age at menopause, parity, breastfeeding, number of pregnancies, and number of abortion as risk factors for BC has been reported in several epidemiological studies conducted around the world.,, According to available literature, changes in reproductive patterns including low parity, late pregnancies, and shorter breastfeeding increase the risk of BC in women. Previous studies have also shown that prolonged exposure to endogenous estrogen due to early menarche, late age at first delivery, and late menopause or exogenous exposure mainly due to hormone replacement therapy or use of oral contraceptive pills are associated with BC. The association of some factors, such as spontaneous and induced abortion, with BC is still controversial., Also, evidence indicates that women who have their first full-term pregnancy after the age of 25 have a higher risk of BC than women who have their first pregnancy before the age of 25.,, The incidence rate of BC is growing fast, especially in Asian countries, caused by changes in lifestyle and reproductive risk factors. According to data from the national cancer registry system of Iran from 2005 to 2014 (10 years), BC is the most common cancer in women and includes 26% of women cancers and 12% of cancers in both sexes. The cause of increased incidence of cancer in Iranian women aged 25 to 55 is breast cancer. In Iran, 67.6% of affected women are in the age range of 35–60 years. In addition to the higher direct costs forced on patients and providers, the conflict of more years of life and failure to undertake social activities in these women causes a great economic burden on society.,
According to the evidence, variations in the patterns of risk factors illustrate the international variation in the burden of BC. Therefore, awareness of BC risk factors could improve the prevention of this cancer. Despite the importance of BC as the most common cancer in the Iranian female population, there is a dearth of systematic review (SR) and meta-analysis (MA) on risk factors of BC in Iran. The present study aimed to investigate the relationship between menstrual and reproductive factors and BC in Iranian women. To the best of our knowledge, this is the first SR and MA on the menstrual and reproductive risk factors of BC in Iran.
| Methods|| |
PRISMA guidelines were used to report this SR and MA.
Search strategy: To identify the relevant studies, we used computer-based search in databases of PubMed, Web of Science, Scopus, and Persian databases including SID and Magiran until February 23, 2020. Cochrane database was also searched and no article was found and the papers that were extracted from “Web of Science” and “Magiran” were duplicates. The search terms used to identify the studies were: “risk factor” OR “reproductive factors” OR “menstrual factors” OR “reproductive history” AND “breast cancer” OR “breast carcinoma” OR “breast neoplasm” AND “Iran” OR “Persian” and their Persian equivalents. Hand searching of articles referenced by the retrieved studies was performed to increase the search sensitivity. The steps of study selection are shown in [Figure 1].
Screening (inclusion and exclusion criteria): The retrieved studies were eligible for inclusion in this SR and MA if they 1) were observational studies; 2) the full text of article was accessible; 3) quantified the reproductive or menstrual risk factors; 4) reported risk ratios, odds ratios, hazard ratios, and 95% CIs; and 5) BC incidence was confirmed by histopathology in hospitalized sample or being registered as case of diagnosed BC in cancer registry in Iranian females. There were no limitations on language or publication date. Excluded studies were 1) animal or genetic articles and 2) review articles, editorials, letters, case reports, meeting abstracts, and nonpeer-reviewed articles.
Study selection: Two authors independently checked the titles and abstracts for each study and collected and analyzed potentially relevant studies for eligibility; disagreements were addressed by discussion and otherwise were settled by a third author.
Data extraction: The data were extracted by two researchers (EM and an assistant) independently. The extracted items included authors' name, publication year, study design, sample size, number of BC cases and controls, data collection, sources of BC-related information, and adjusted covariate(s). The included menstrual and reproductive risk factors were age at first live childbirth, age at menarche, history of abortion, nulliparity, having a history of breastfeeding, and menopausal status.
Quality assessment: Two researchers (EM and an assistant) evaluated independently the methodological quality of individual studies with the Newcastle-Ottawa Scale (NOS) to assess the quality of nonrandomized studies, with all disagreements settled by a third author. NOS implemented the star system with a maximum of nine stars scoring from 0 to 9. In this way, 7–9 stars indicated high quality, 4–6 stars showed moderate quality, and 0–3 stars meant low quality.
Data synthesis and statistical methods
The following exposures were extracted from eligible articles: menopausal status (menopausal status means whether a woman has experienced menopause or not) and age at menarche (<12 years and ≥12 years) as menstrual factors. Also, age at first live childbirth (<20 years and ≥20 years), parity (parous vs. nulliparous), breastfeeding (yes/no), and history of abortion (yes/no) deemed as reproductive factors. This study included all forms of BC regardless of their pathological aspects or tumor stage. We selected the most recent study if data from the same population were used in multiple articles.
Because all of the included studies were case–control, odds ratios (ORs) were used to evaluate the association of menstrual as well as reproductive risk factors and BC. The pooled measure was determined as the inverse variance weighted mean of the natural logarithm of OR with 95% CI. Adjusted OR was preferred over crude measures whenever it was available. If more than one measure of association between each of prognostic factors and the odds of BC was available in a study, the approach of combining effect sizes through multiple comparisons in individual studies introduced by Borenstein. et al. was used. We used random effects model and combined study specific OR (95% CI), which considers both within-study and between-studies variation. If the Q-test, a standardized measure of the deviation of the effect of each study from the overall effect, was statistically significant (P < .05), or if the variance between studies as a percentage of the total variance (I2 statistic) was more than 20%, there was heterogeneity of effect size between studies., Subgroup analyses were conducted so as to further assess ORs in the subset of studies. Publication bias was explored visually with funnel plots, and quantitatively using the Egger and Begg statistical tests. The trim and fill approach was used to further investigate publication bias., Statistical significance was considered as P < 0.05. Stata version 11.2 (StataCorp, College Station, Texas) was used for all analyses.
| Results|| |
Identification and description of studies
In the initial search, 134 studies were identified, of which 44 studies were duplicates and 39 studies were removed after assessing the title and abstract. The remaining 51 studies were carefully reviewed and 24 articles were excluded for the reasons demonstrated in [Figure 1]. Finally, 27 studies fulfilled all the inclusion criteria [Figure 1].
Except of five studies,,,,, one or more risk factors of BC were adjusted in all included studies. All studies were published during 2002–2019, and most were published in 2011.,,,,, Six studies had “high”,,,,, and 21 articles,,,,,,,,,,,,,,,,,,,, had moderate quality assessment score [Table 1].
Association between menstrual factors and BC
The data of 7 studies with a sample size of 15260 (1754 cases and 13506 controls) revealed that menarche age (with control group < 12 years)) OR = 0.55 95% CI: 0.29–1.03, P < 0.001, I2 = 84.9%, P = 0.062 (was not associated with increased risk of BC [Table 2], [Figure 2]. According to the data of 15 studies with a sample size of 44046 (3043 cases and 41003 controls), menopausal status (with premenopause as control group) was associated with higher risk of BC (OR = 1.60 95% CI: 1.18–2.17, P < 0.001, I2 = 92.9%, P = 0.002) [Table 2], [Figure 3].
|Figure 2: Forest plot of the relationship between age at menarcheal and breast cancer using the random effects model|
Click here to view
|Figure 3: Forest plot of the relationship between menopausal status and breast cancer using the random effects model|
Click here to view
|Table 2: Overall and subgroup pooled odds ratios for the association of BC with menstrual and reproductive factors|
Click here to view
Association between reproductive factors and BC
In reproductive factors, according to the results of 12 studies with a sample size of 5513 (2221 cases and 3292 controls), there was no association between the history of abortion with an increased risk of BC (OR = 1.21 95% CI: 0.97–1.5, P < 0.001, I2 = 79.3%, P = 0.1) [Table 2], [Figure 4]. Also, nulliparity did not increase the risk of BC (OR = 1.43 95% CI: 0.89–2.31, P < 0.005, I2 = 65.7%, P = 0.141) (8 studies, sample size 16098, 2112 cases and 13986 controls) [Table 2], [Figure 5]. There was an increased risk of BC in first pregnancy after 20 years old (OR = 1.79 95% CI: 1.36–2.35, P < 0.001, I2 = 79.6%, P = 0.001) in 10 studies with a sample size of 4716 (2239 cases and 2477 controls) [Table 2], [Figure 6]. Also, the history of breastfeeding was not related to higher BC risk (OR = 0.68 95% CI: 0.42–1.09, P < 0.001, I2 = 81.3%, P = 0.108) based on 8 studies with a sample size of 4209 (1694 cases and 2515 controls) [Table 2], [Figure 7].
|Figure 4: Forest plot of the relationship between abortion and breast cancer using the random effects model|
Click here to view
|Figure 5: Forest plot of the relationship between nulliparity and breast cancer using the random effects model|
Click here to view
|Figure 6: Forest plot of the relationship between first pregnancy age and breast cancer using the random effects model|
Click here to view
|Figure 7: Forest plot of the relationship between breastfeeding and breast cancer using the random effects model|
Click here to view
Subgroup analyses were conducted based on quality score (high or moderate), adjustment of studies for risk factors (yes or no), source of BC information (hospital-based or registry), and geographical area (north, south, west, east, and center of Iran) regarding each of examined menstrual and reproductive risk factors, separately. A significant increase in BC risk was identified in some of the subgroups [Table 2].
The funnel plots and Egger and Begg tests for abortion did not provide substantial evidence on the publication bias (Egger: P =0.27; Begg: P =0.22). Also, Egger and Begs tests (Egger: P =0.80; Begg: P =0.46) and the funnel plot for Breastfeeding did not provide evidence for the publication bias. Furthermore, based on the results of Egger and Begg tests and funnel plots, there was no publication bias for menarche age (Egger: P =0.28; Begg: P =0.29) and nulliparity (Egger: P =0.22; Begg: P =0.46). However, Egger and Begs tests and the funnel plot for menopausal status (Egger: P <0.001; Begg: P =0.66) and age at first pregnancy (Egger: P <0.001; Begg: P =0.93) provided evidence for the publication bias (Appendix). For further assessment on publication bias for menopausal status and age at first pregnancy, we used trim and fill approach., In this imputation method, no study was imputed in menopausal status but for age at first pregnancy, two hypothetically missing studies were imputed and the “adjusted” point estimate suggested similar OR compared with the original analysis (OR = 1.63, 95% CI = 1.29–2.07).
| Discussion|| |
The present SR and MA focused on some menstrual and reproductive factors effect on the risk of BC in Iranian female population. The results showed that there is no significant relationship between menarche age and BC in Iranian women. But postmenopausal women were at higher risk for BC than premenopausal women. In a MA conducted to assess the relationship between early menarche and menopausal status with BC in Iranian women, the data of 12 case–control studies revealed that the odds of BC was significantly higher in the women with early menarche and the data of twenty case–control studies showed that the relationship between menopausal status and BC was not statistically significant. But in studies by Namiranian et al. and Besharat et al., the relationship between early menarche and BC was not statistically significant. Another MA of Iranian studies reported no relationship between menstrual factors (age of menarche; menopausal status) and BC risk. As it can be seen, different results have been obtained in similar populations. The reason for inconsistency in our results and study by Zahmatkesh et al. might be due to the difference in reviewed databases, included studies, and time range of published studies in meta-analyses. In a MA conducted on Indian women, early age at menarche and menopause had 85% and 35% more risk of BC, respectively. A MA of Southeast Asian women also showed that menopausal status was a risk factor for BC. Different findings may be due to differences in ethnicity, different lifestyles in countries, and the method of the study. Some studies in Turkey,, Bahrain, and Kuwait have identified early menarche as a risk factor for BC. But in other studies in Turkey,, Pakistan, and Saudi Arabia, as in the present study, early menarche was not reported as a risk factor for BC. Also, some studies in Pakistan, Turkey, and Iraq, similar to the present study, have reported postmenopausal status as a risk factor for BC, while some studies in Turkey have reported inconsistent results.
Our results showed the only reproductive factor associated with an elevated risk of BC was older age at first pregnancy. But, there was no clear statistical relationship between abortion, nulliparity, and breastfeeding with BC. However, in the subgroup analysis for the history of abortion, high-quality studies and adjusted studies for BC risk factors showed a positive relationship between abortion and BC. According to a study by Besharat et al., nulliparity was not associated with the risk of BC. Also, in women who had more than a total of about 5 years of breastfeeding, the chance of developing BC was not statistically significant. Other independent studies also supported these results.,, Another MA by Mao et al. (2019) on Chinese women found an overall lower risk of BC for parous women, compared with nulliparous women. Also, this study indicated that early age at first childbirth is a protective factor for BC that is consistent with our study. A MA on Indian women has reported that age at first childbirth, breastfeeding, and nulliparity are all related to increased risk of BC. The results of the mentioned study are not consistent with our study in terms of the relationship between breastfeeding and nulliparity with BC. On the other hand, according to the results of this study, in women with late first pregnancy, the risk of BC is increased, which is consistent with the current study. In meta-analyses, which were done on the data related to the Korean and Southeast Asian women,, age at first pregnancy and the total period of breastfeeding and nulliparity were associated with an elevated risk of BC. In an SR and MA by Namiranian et al. (2014) on the Eastern Mediterranean Region, the highest risk factor for BC was having no live birth. Also, age at first pregnancy more than 30 years old increased the risk of BC, which is congruent with the results of the present study. In subgroup analysis, breastfeeding had a preventive relationship with BC in studies conducted in north and west of Iran. Maybe the different breastfeeding patterns of the mothers must be considered in different regions.
Also, the results of the studies in Middle Eastern countries on the relationship between old age at first pregnancy and BC are contradictory. In some studies in Turkey,,, older age at first pregnancy has been reported as a risk factor for BC, which is consistent with the present study, whereas some studies in Turkey,, Pakistan, and Saudi Arabia have yielded conflicting results. Overall, it seems that there are possible geographical differences in incidence and risk factors of BC due to racial variations, family history, and disease background, stress level, nutritional culture, environmental pollutions, and lifestyle.
About the relationship between abortion and BC, in an SR conducted by Yeganeh et al. (2018), out of 25 articles examining abortion, 15 reported positive and 10 reported no relation between abortion and BC. The Collaborative Group on Hormonal Factors in BC published a MA that showed no difference in the risk of BC development in women who had one or more spontaneous or induced abortions. These results were further supported by another cohort study in women from California. The findings of these studies and another study of Saudi Arabia are in line with the current study. However, many studies from Asia and Middle Eastern countries maintain the existence of a strong link between first-trimester abortions and BC risk.,, But two MA studies, and Expert committee opinions by both American College of Obstetricians and Gynecologists and National Cancer Institute revealed that there was no significant relationship between induced abortion and BC in Chinese women. The considerable problem in studies about abortion is that abortion is illegal in some countries, so studies conducted in these countries may report abortion rate less than its real rate. Therefore, in the present MA, given that the study population is from Iran, a country with restrictive regulations regarding abortion, the findings should be considered with caution. At the same time, in the subgroup with high-quality studies and the studies conducted in the west and east areas of Iran, this relationship was significant. According to the present study, although abortion and nulliparity were not considered risk factors for BC, abortion in the eastern and western regions of Iran and nulliparity in the central regions of Iran showed a significant relationship with BC. Also, in the northern and western regions of Iran, breastfeeding showed a preventive relationship with BC. In explaining this issue, we should mention the differences in access to screening and diagnostic services, genetic and racial differences, differences in household size, and access to reproductive health services in Iran provinces.
Strength: Previous meta-analyses focused on a risk factor and its various levels of exposure; however, our results focus on several factors regarding its identical exposure in Iranian women. Also, in the present MA, the risk factors of BC were examined by geographical regions of Iran, separately.
Limitation: This SR had several limitations. The first limitation was the availability and quality of the published data. Many studies did not include some statistical parameters (i.e., OR, CI), and the control groups of each risk factor were different. Hence, we had to exclude some studies of MA. Second, all of the included studies in this MA were case–control, so we need trials with high methodological quality including prospective cohort studies, as those are less susceptible to bias. It seems that in studies on these issues in Iran, there is a need for higher accuracy and quality in the method of performing and reporting the results of individual studies. Third, in most of the included studies in this MA, the sampling was hospital-based which may be convenient and inexpensive to collect but may be biased by factors such as age, socioeconomic status, and physical condition, that affect the likelihood of hospitalization for cases and controls. It is recommended that information of cancer registry or population-based control groups be used in future studies.
| Conclusions|| |
Our findings revealed that menopausal status and first pregnancy age were shown to be significantly associated with increased BC risk, whereas menarche age, nulliparity, and breastfeeding were not associated with higher BC risk among Iranian females. In regard to the history of abortion, our findings revealed no association with abortion and BC, but in high-quality studies and adjusted studies for risk factors of BC, the relationship between abortion and BC was significant. The inconsistencies between our findings and other studies from other countries might be due to differences in race, stress level, nutritional culture, environmental pollutions, and lifestyle.
The present SR and MA is part of the first author's Ph.D. thesis under code of ethics: IR.MUMS.NURSEREC.1397.034, (Grant ID: 970008).
Financial support and sponsorship
This manuscript is part of Ph.D. thesis of the first author approved by Mashhad University of Medical Sciences, Mashhad, Iran, under the code of IR.MUMS.NURSEREC.1397.034 (Grant ID: 970008).
Conflicts of interest
There are no conflicts of interest.
| Appendix|| |
Funnel Plots for publication bias
| References|| |
Bray F, Ferlay J, Soerjomataram I, Siegel RL, Torre LA, Jemal A. Global cancer statistics 2018: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin 2018;68:394-424.
Khakbazan Z, Taghipour A, Roudsari RL, Mohammadi E, Omranipour R. Delayed presentation of self-discovered breast cancer symptoms in Iranian women: A qualitative study. Asian Pac J Cancer Prev 2014;15:9427-32.
Zendehdel M, Niakan B, Keshtkar A, Rafiei E, Salamat F. Subtypes of benign breast disease as a risk factor for breast cancer: A systematic review and meta-analysis protocol. Iran J Med Sci 2018;43:1-8.
Manouchehri E, Taghipour A, Ghavami V, Ebadi A, Homaei F, Roudsari RL. Night-shift work duration and breast cancer risk: An updated systematic review and meta-analysis. BMC Womens Health 2021;21:1-16.
Karim SM, Baeshen W, Neamatullah SN, Bin B. Oral contraceptives, abortion and breast cancer risk: A case control study in Saudi Arabia. Asian Pac J Cancer Prev 2015;16:3957-60.
Mehdipour P, Pirouzpanah S, Kheirollahi M, Atri M. Androgen receptor gene CAG repeat polymorphism and breast cancer risk in Iranian women: A case-control study. Breast J 2011;17:39-46.
Parsa P, Parsa B. Effects of reproductive factors on risk of breast cancer: A literature review. Asian Pac J Cancer Prev 2009;10:545-50.
Inumaru LE, Irineu Gomes Duarte Quintanilha M, Aparecida da Silveira É, Veloso Naves MM. Risk and protective factors for breast cancer in Midwest of Brazil. J Environ Public Health 2012. doi: 10.1155/2012/356851.
Hosseinzadeh M, Eivazi Ziaei J, Mahdavi N, Aghajari P, Vahidi M, Fateh A, et al
. Risk factors for breast cancer in Iranian women: A hospital-based case-control study in Tabriz, Iran. J Breast Cancer 2014;17:236-43.
Dianatinasab M, Fararouei M, Mohammadianpanah M, Zare-Bandamiri M, Rezaianzadeh A. Hair coloring, stress, and smoking increase the risk of breast cancer: A case-control study. Clin Breast Cancer 2017;17:650-9.
Ebrahimi M, Vahdaninia M, Montazeri A. Risk factors for breast cancer in Iran: A case-control study. Breast Cancer Res 2002;4:R10.
Montazeri A, Jarvandi S, Ebrahimi M, Haghighat S, Ansari M. The role of depression in the development of breast cancer: Analysis of registry data from a single institute. Asian Pac J Cancer Prev 2004;5:316-9.
Youlden DR, Cramb SM, Yip CH, Baade PD. Incidence and mortality of female breast cancer in the Asia-Pacific region. Cancer Biol Med 2014;11:101-15.
Akbari A, Khayamzadeh M, Salmanian R, Motlagh AG, Roshandel G, Nouri M, et al
. National Cancer Mortality-to-Incidence Ratio (MIR) in Iran (2005-2014). Int J Cancer Manag 2019;12:e94145.
Jazayeri SB, Saadat S, Ramezani R, Kaviani A. Incidence of primary breast cancer in Iran: Ten-year national cancer registry data report. Cancer Epidemiol 2015;39:519-27.
Davari M, Yazdanpanah F, Aslani A, Hosseini M, Nazari AR, Mokarian F. The direct medical costs of breast cancer in Iran: Analyzing the patient's level data from a cancer specific hospital in Isfahan. Int J Prev Med 2013;4:748-54.
Davari M, Mokarian F, Hoseini M, Aslani A, Nazari A, Yazdanpanah F. Direct Medical Costs of Breast Cancer in Iran, Analyzing Patients Level Data from a Cancer Specific Hospital in Isfahan, Iran. Health Inf. Manag. J. 2013;10:1-10.
Crew KD, Gammon MD, Terry MB, Zhang FF, Zablotska LB, Agrawal M, et al
. Polymorphisms in nucleotide excision repair genes, polycyclic aromatic hydrocarbon-DNA adducts, and breast cancer risk. Cancer Epidemiol Biomarkers Prev 2007;16:2033-41.
Tazhibi M, Dehghani M, Babazadeh S, Makkarian F, Tabatabaeian M, Sadeghi M, et al
. Hormonal and reproductive risk factors associated with breast cancer in Isfahan patients. J Educ Health Promot 2014;3:69.
Moher D, Liberati A, Tetzlaff J, Altman DG, PRISMA group. Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement. Int J Surg 2010;8:336-41.
McElvenny DM, Crawford JO, Davis A, Dixon K, Alexander C, Cowie H, et al
. A review of the impact of shift-work on occupational cancer: Part 1–epidemiological research. Policy Pract. Health Saf. 2018;16:71-108.
Tawfik GM, Dila KAS, Mohamed MYF, Tam DNH, Kien ND, Ahmed AM, et al
. A step by step guide for conducting a systematic review and meta-analysis with simulation data. Trop Med Health 2019;47:1-9.
Borenstein M, Hedges LV, Higgins JP, Rothstein HR. Introduction to Meta-Analysis. John Wiley and Sons; 2011. 239-42 p.
DerSimonian R, Laird N. Meta-analysis in clinical trials. Controlled Clinical Trials 1986;7:177-88.
Borenstein M, Hedges LV, Higgins JP, Rothstein HR. Introduction to Meta-Analysis. John Wiley and Sons; 2009. p. 107-17.
Higgins JP, Thompson SG. Quantifying heterogeneity in a meta-analysis. Stat Med 2002;21:1539-58.
Egger M, Smith GD, Schneider M, Minder C. Bias in metaanalysis detected by a simple, graphical test. BMJ Open 1997;315:629-34.
Begg CB, Mazumdar M. Operating characteristics of a rank correlation test for publication bias. Biometrics 1994;50:1088–101.
Duval S, Tweedie R. A nonparametric “trim and fill” method of accounting for publication bias in meta-analysis. J Am Stat Assoc 2000;95:89-98.
Duval S, Tweedie R. Trim and fill: A simple funnel-plot–based method of testing and adjusting for publication bias in meta-analysis. Biometrics 2000;56:455-63.
Ebrahimi M, Montazeri A. Investigating the reproductive risk factors in patients with breast cancer. Paiesh 2002;1:23-7.
Razmara L HK, Talaiezadeh AH, Tahmasebi M, Karandish M. Relationship between fish consumption and decreased breast cancer risk. Sci Med J 2010;9:307-16.
Sepandi M, Akrami M, Tabatabaee H, Rajaeefard A, Tahmasebi S, Angali KA, et al
. Breast cancer risk factors in women participating in a breast screening program: A study on 11,850 Iranian females. Asian Pac J Cancer Prev 2014;15:8499-502.
Zare N, Haem E, Lankarani KB, Heydari ST, Barooti E. Breast cancer risk factors in a defined population: Weighted logistic regression approach for rare events. J Breast Cancer 2013;16:214-9.
Sharifzadeh GhR. HM, Kermani T, Ataiee M, Akhbari SH. Breast cancer and the related factors: A case control study. J Birjand Univ Med Sci 2011;17:191-9.
Hajian-Tilaki K, Kaveh-Ahangar T. Reproductive factors associated with breast cancer risk in northern Iran. Med Oncol 2011;28:441-6.
Ghiasvand R, Maram ES, Tahmasebi S, Tabatabaee SHR. Risk factors for breast cancer among young women in southern Iran. Int J Cancer 2011;129:1443-9.
Akbari A, Razzaghi Z, Homaee F, Khayamzadeh M, Movahedi M, Akbari ME. Parity and breastfeeding are preventive measures against breast cancer in Iranian women. Breast cancer 2011;18:51-5.
Moradinazar M, Marzbani B, Shahebrahimi K, Shahabadi S, Marzbani B, Moradinazar Z. Hormone therapy and factors affecting fertility of women under 50-year-old with breast cancer. Breast Cancer 2019;11:309-19.
Mahouri K, Dehghani Zahedani M, Zare S. Breast cancer risk factors in south of Islamic Republic of Iran: A case-control study. East Mediterr Health J 2007;13:1265-73.
Keihanian Sh GF, Fotookian Z, Shoormij R, Saravi M. To investigation the cancer risk factors in Ramsar and Tonekabon. J. Qazvin Univ. Med. Sci. Health Serv. 2010;14:12-9.
Jafarinia B, Bahadorzai M, Delpisheh A, Sayehmiri K, Tavakoli M. Risk factors of breast cancer in Dezful city of Iran: A case-control study. Tehran Univ Med J 2016;74:135-9.
Marzbani B, Taymoori P, Nouri B. Assessment of risk factors for breast cancer among women under 50 years old. Journal of School of Public Health and Institute of Public Health Research 2017;15:47-60.
Zayeri F, Seyedagha S, Aghamolaie H, Boroumand F, Yavari P. Comparison of the logistic regression and classification tree models in determining the risk factors and prediction of breast cancer. Iran J Epidemiol 2016;12:49-57.
Pesaran Z, Rezaei A, Kia RT, Siydat A. Evaluation of breast cancer risk factors for using in hormone replacement therapy of corticosteroid- treated post-menopausal women. J Shahrekord Univ Med Sci 2003;5:70-5.
Amini Sani N SM, Ehdaeivand F, Mardi A. Investigating the relationship between abortion and breast cancer risk in women living in Mashhad: A case control study. Res Scientific J Ardabil Univ Med Sci health Serv 2003;2:7-12.
Holakouie Naieni KH, Ardalan A, Mahmoodi M, Motevalian A, Yahyapoor Y, Yazdizadeh B. Risk factors of breast cancer in north of Iran: A case-control in Mazandaran Province. Asian Pac J Cancer Prev 2007;8:395.
Yavari P, Mosavizadeh M, Sadrol-Hefazi B, Mehrabi Y. Reproductive characteristics and the risk of breast cancer--A case-control study in Iran. Asian Pac J Cancer Prev 2005;6:370-5.
Tehranian N, Shobeiri F, Pour FH, Hagizadeh E. Risk factors for breast cancer in Iranian women aged less than 40 years. Asian Pac J Cancer Prev 2010;11:1723-5.
Lotfi M, Charkhati S, Shobeyri S. Breast cancer risk factors in an urban area of Yazd city, Iran. Acta Med Iranica 2008;46:258-64.
Joukar F, Ahmadnia Z, Atrkar-Roushan Z, Hasavari F, Rahimi A. The investigation of risk factors impacting breast cancer in Guilan Province. Asian Pac J Cancer Prev 2016;17:4623-9.
Moosazadeh M, Zaboli E, Alizadeh-Navaei R, Ranjbaran H, Amjadi O, Faghih M, et al
. Association between anthropometric indices and breast cancer based on the data of the enrolment phase (cross-sectional) in Tabari cohort study: The causal relationship or violation of temporality. J Mazandaran Univ Med Sci 2019;29:64-71.
Zahmatkesh BH, Keramat A, Alavi N, Khosravi A, Chaman R. Role of menopause and early menarche in breast cancer: A meta-analysis of Iranian studies. Nurs Midwifery Stud 2017;6:e37712.
Namiranian N, Moradi-Lakeh M, Razavi-Ratki SK, Doayie M, Nojomi M. Risk factors of breast cancer in the Eastern Mediterranean Region: A systematic review and meta-analysis. Asian Pac J Cancer Prev 2014;15:9535-41.
Besharat S, Motie MR, Besharat M, Roshandel G. Breast cancer risk factors in women of Golestan Province in Iran: A case-control study. Iran J Obstet Gynecol Infertil 2011;13:46-51.
Jafari-Mehdiabad F, Savabi-Esfahani M, Mokaryan F, Kazemi A. Relationship between breastfeeding factors and breast cancer in women referred to Seyed Al-Shohada Hospital in Isfahan, Iran. Iran J Nurs Midwifery Res 2016;21:622-7.
Vishwakarma G, Ndetan H, Das DN, Gupta G, Suryavanshi M, Mehta A, et al
. Reproductive factors and breast cancer risk: A meta-analysis of case–control studies in Indian women. South Asian J Cancer 2019;8:80-4.
] [Full text]
Nindrea RD, Aryandono T, Lazuardi L. Breast cancer risk from modifiable and non-modifiable risk factors among women in Southeast Asia: A meta-analysis. Asian Pac J Cancer Prev 2017;18:3201-6.
Dogan N, Toprak D. Female breast cancer mortality rates in Turkey. Asian Pac J Cancer Prev 2014;15:7569-73.
Kuru B, Ozaslan C, Ozdemir P, Dinç S, Camlibel M, Alagöl H. Risk factors for breast cancer in Turkish women with early pregnancies and long-lasting lactation. Acta Oncol 2002;41:556-61.
Albeshan SM, Mackey MG, Hossain SZ, Alfuraih AA, Brennan PC. Breast cancer epidemiology in gulf cooperation council countries: A regional and international comparison. Clin Breast Cancer 2018;18:e381-92.
Ozsoy A, Barça N, Dolek BA, Aktaş H, Elverici E, Araz L, et al
. The relationship between breast cancer and risk factors: A single-center study. Eur J Breast Health 2017;13:145-9.
Gokdemir-Yazar O, Yaprak S, Colak M, Yildirim E, Guldal D. Family history attributes and risk factors for breast cancer in Turkey. Asian Pac J Cancer Prev 2014;15:2841-6.
Shamsi U, Khan S, Usman S, Soomro S, Azam I. A multicenter matched case control study of breast cancer risk factors among women in Karachi, Pakistan. Asian Pac J Cancer Prev 2013;14:183-8.
Gad ZM, Elhafeez SSA, Ghareeb KAH, Shwana S, Al Talabani BGM, Taha DA, et al
. An epidemiological study of female breast cancer in Sulaymaniyah City, Iraqi Kurdistan. Tabari Biomed Stu Res J 2020;2:13-21.
Nojomi M, Mirfakhraee R, Hosseini N. Relationship between hormonal factors and breast cancer. Hakim Health Syst Res J 2004;7:19-25.
Peterson NB, Huang Y, Newcomb PA, Titus-Ernstoff L, Trentham-Dietz A, Anic G, et al
. Childbearing recency and modifiers of premenopausal breast cancer risk. Cancer Epidemiol Prev Biomarkers 2008;17:3284-7.
Mao J, Shi J, He S, Li N, Shi J, Yang F. Reproductive factors and risk of breast cancer: A pooled meta-analysis of 55 case-control studies based on different source populations. Int J Clin Exp Med 2019;12:6453-68.
Park B, Park S, Shin H-R, Shin A, Yeo Y, Choi J-Y, et al
. Population attributable risks of modifiable reproductive factors for breast and ovarian cancers in Korea. BMC Cancer 2016;16:5.
Li H, Sun X, Miller E, Wang Q, Tao P, Liu L, et al
. BMI, reproductive factors, and breast cancer molecular subtypes: A case-control study and meta-analysis. J Epidemiol 2017;27:143-51.
Alim NE, Kiziltan G. Assessment of risk factors of obesity and diet on breast cancer in Ankara, Turkey. Pak J Med Sci 2016;32:1537-42.
Yeganeh Z, Sheikhan Z, Kariman N, Hajian P, Nasiri M, Mirzadeh N. Relationship between pregnancy-related variables and risk of breast cancer: Systematic review. Iran J Obstet Gynecol Infertil 2018;21:85-97.
Beral V, Bull D, Doll R, Peto R, Reeves G; Collaborative Group on Hormonal Factors in Breast Cancer. Breast cancer and abortion: Collaborative reanalysis of data from 53 epidemiological studies, including 83 000 women with breast cancer from 16 countries. Lancet 2004;363:1007-16.
Henderson KD, Sullivan-Halley J, Reynolds P, Horn-Ross PL, Clarke CA, Chang ET, et al
. Incomplete pregnancy is not associated with breast cancer risk: The California teachers study. Contraception 2008;77:391-6.
Huang Y, Zhang X, Li W, Song F, Dai H, Wang J, et al
. A meta-analysis of the association between induced abortion and breast cancer risk among Chinese females. Cancer Causes Control 2014;25:227-36.
Brind J, Condly SJ, Lanfranci A, Rooney B. Induced abortion as an independent risk factor for breast cancer: A systematic review and meta-analysis of studies on South Asian women. Issues Law Med 2018;33:32-54.
Ozmen V, Ozcinar B, Karanlik H, Cabioglu N, Tukenmez M, Disci R, et al
. Breast cancer risk factors in Turkish women–A University Hospital based nested case control study. World J Surg Oncol 2009;7:37.
Deng Y, Xu H, Zeng X. Induced abortion and breast cancer: An updated meta-analysis. Medicine 2018;97:e9613.
Guo J, Huang Y, Yang L, Xie Z, Song S, Yin J, et al
. Association between abortion and breast cancer: An updated systematic review and meta-analysis based on prospective studies. Cancer Causes Control 2015;26:811-9.
ACOG Committee Opinion No. 434: Induced abortion and breast cancer risk. Obstet Gynecol 2009;113:1417-8.
National Cancer Institute. Summary report: Early reproductive events and breast cancer workshop. Issues Law Med 2005;21:161-5.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7]
[Table 1], [Table 2], [Table 1], [Table 2]