Menopause means the permanent cessation of menstruation due to loss of ovarian follicular function, which occurs at a mean age of 51 years normally. It is expected that a woman will spends almost a third of her life beyond the menopause. After the menopause, a marker of the end of a woman’s reproductive life, the amount of circulating estrogen falls significantly so the symptoms and disorders related to estrogen deficiency will appear1.

Menopause can occur before the median age of natural menopause (age 51 years) that called early menopause. It is may be occur due to medical or surgical interventions such as chemotherapy or surgical procedures such as oophorectomy2. Some epidemiological studies reported that women who undergo early menopause or premature menopause are under higher risk of all-causes mortalities. However, it is necessary to study more on this controversial issue3.

Menopause can increase the risk of cardiovascular diseases (CVD)4. CVD is the most important cause of mortality and morbidity worldwide5. Over the past decades the importance of CVD among women has been increased. Therefore, researchers have investigated whether there are gender differences in CVD risk. In the past two decades the epidemiological status of CVD has changed dramatically so, that it becomes the source of disease burden in women population6,7.

The importance of CVD among women has been highlighted over past decade, leading researchers to investigate the impact of gender differences in CVD risk factors. In some of these studies mentioned higher CVD risk in postmenopausal women but it is not certainly clear whether menopause is an issue of aging, estrogen deficiency or both6^. Metabolic syndrome (MetS) is used to define the risk of cardiovascular diseases including obesity, dyslipidemia, hypertension and insulin resistance7. Some evidence shows a link between the menopause and some components of the MetS, but results have been inconsistent. There is a hypothesis that the menopause is associated with an increase in the risk of cardiovascular disease independent of normal aging8.

In this study we want to explore the associations between normal and other reasons of menopause with CVD and lipid profile as a risk factor of CVD in a large population-based Iranian samples.

In current cross-sectional study, 1556 postmenopausal women (with amenorrhea for more than a year by questioner or FSH > 30-40 mIU/ml )9, 783 of them include of natural menopause and 773 of them consist of other reason menopause (hysterectomy without oophorectomy or one side oophorectomy, hysterectomy with oophorectomy or two side oophorectomy without hysterectomy), were recruited as part of the Mashhad Stroke and Heart Atherosclerotic Disorders (MASHAD) Study using a cluster-randomized-assigned during 2007-2008, as described previously10. Inclusion criteria were no known history of infectious diseases, nor a family history of stroke, myocardial infarction. Informed consent was obtained from all individuals using approved protocols by the Ethics Committee of Mashhad University of Medical Sciences10.

Data were analyzed using SPSS-18 software (SPSS Inc., IL, and USA). The normality of distribution was evaluated using Kolmogorov–Smirnov test. Descriptive statistics including mean ± standard deviation was considered for normally distributed variables or median ± interquartile range for variables that were not normally distributed. For normally distributed variables, Student’s t-test was applied to compare clinical and baseline demographics characteristics between groups. The Mann-Whitney U test was used for continuous variables and non-normally distributed variables. For categorical parameters, Chi-square or Fisher exact tests were used. All the analyses were two-sided and p value < 0.05 was considered as significant.

Clinical and demographic characteristics of participants are presented in Table 1. Among the subjects 1763, 900 (50.3%) had a natural menopause and 863 (49.7%) subjects had other reasons for the menopause. The mean age was 54.32±3.88 and 48.12±7.06 years for natural menopause and other reasons for the menopause respectively (Table 1).

Our results demonstrated that the mean of BMI was significantly higher in other reasons of menopause than natural menopause status (p< 0.05). But WC was significantly lower in other reasons of menopause than natural menopause (p< 0.05). Also, there were not significant differences between two groups in HC, mid upper circumference, systolic and diastolic blood pressure (p>0.05).

According to our findings the levels of LDL, BUN, creatinine, AST were significantly higher in the natural menopause group, whereas uric acid and hs-CRP were meaningfully lower in natural menopause group compared with the group of other reasons for the menopause (p< 0.05). But no statistically differences were found in HC, MC, SBP, DBP, glucose, triglyceride, HDL, total and direct bilirubin, and ALT between natural menopause groups and other reasons for menopause groups (Table 1). Moreover, depression and anxiety score in other reasons of menopause group were significantly higher than natural menopause groups.

We also compared the level of different hematological parameters of the participants between natural menopause group and other reasons of menopause group. Results presented in Table 2 clearly defined that individuals with a natural menopause had a significantly higher level of MCHC and platelets than the other groups (p<0.05). In contrast, the level of WBC was lower in the natural menopause group (p<0.05) (Table 2). But there were no expressive differences between groups with regard to RBC, HCT, Hb, MCV, MCH, RDW, PDW and MPV.

Logistic regression analysis was performed to determine the odds ratio (OR) of the association between demographic, biochemical and hematological (Table 3). Results obtained from univariate analysis demonstrated that BMI, WC, LDL, BUN, creatinine, AST and MCHC are associated with menopause, but when multivariate analysis was done with entering age and all factors in table to model, BMI, WC, BUN, uric acid, AST, MCHC and platelets are an independent predictive risk factor for menopause (Table 3).