Document Type : Original Article
Authors
1 Mother and Child Care Research Center, Hamadan University of Medical Sciences, Hamadan, Iran
2 Department of Entomology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran
Abstract
Keywords
Age at menopause is naturally influenced by a
variety of racial, environmental, and physiological
factors (
Postmenopausal women are reported more than
15% of the population in developed countries, but
this rate is 5-8% in less developed regions of the world. By 2030, the world population of menopausal
and postmenopausal women is assumed
to increase to 1.2 billion, with 47 million new
cases each year. As women are spending more
than 1/3 of their life in the postmenopausal period
and the number of postmenopausal women
is increasing, physical and mental health in this
period are of greater importance. Identifying
the factors associated with late or early menopause
is necessary because age at menopause
has been associated with risk for the onset of
several chronic diseases such as cardiovascular
diseases, breast and endometrial cancers and osteoporosis
(
The major role of ethnicity in determining age
at menopause as well as its main predictors has
been assessed in different societies. It is noted
that Hispanic and African-American women
reach menopause earlier, while Chinese and
Japanese women reach menopause later than
the average Caucasian women experiencing
menopause at about age 51.5 (
This descriptive-analytic study was carried out on 400 postmenopausal women aged 43 to 65 years old attending the health centers in Hamadan, Hamadan Province, West of Iran, for general counseling or treatment of menopausal symptoms, during 2013. The study was performed according to the Helsinki declaration protocol. The objectives of the study were explained to all participants and informed consent was then obtained from them. The study was approved by the Ethical Committee of Hamadan University of Medical Sciences. Inclusion criteria were as follows: natural cessation of menses ≥12 months, not being surgically menopause and not receiving hormone therapy. Due to potential effects of oral contraceptive pills (OCP) on age of menopause, we considered two groups of women with and without OCP use using cluster sampling method. The participants were interviewed to record baseline information regarding menarche age (year), marital status (married), age of first and last pregnancy (year), number of parity, quality of menstrual cycle (regularity), duration of breast feeding (year), history of cigarette smoking, level of physical activity (hour/week), as well as socioeconomic status.
Results were reported as mean ± standard deviation (SD) for the quantitative variables and as absolute frequencies and percentages for categorical variables. Categorical variables were compared using chi-square test or Fisher’s exact test when more than 20% of cells with expected count of less than 5 were observed. Continuous variables were also compared using t test. Predictors showing a statistically significant relation with menopausal age in univariate analysis were taken for multivariate logistic regression analysis to investigate their independence as predictors. Odds ratio (OR) and 95% confidence intervals (CI) were calculated. P values of 0.05 or less were considered statistically significant. All the statistical analyses were performed using the Statistical Package for the Social Sciences (SPSS; SPSS Inc., Chicago, IL, USA) version 15.0.
Findings showed that the mean age of women was 57.4 ± 5.1 years, of which 1.3% were less than 45 years, 9.0% were aged 46 to 50 years, 29% were aged 51 to 55 years, and 60.8% were aged 56 years or more. The mean menarche age was 13.6 ± 1.3 years, the mean age at marriage was 15.8 ± 3.6 years, and the mean age at first pregnancy was 18.4 ± 3.5. The mean age of natural menopause was 49.6 ± 4.02 years and its median was 50.0 years. Among them, 17/5% were ≤45 years old, 45% were 50-46 years old, and 37/5% were ≥51 years old.
The baseline characteristics of participants in the
two groups are summarized in table 1. Except for
history of infertility that was more frequent in OCP
non-users as well as weekly physical activity that
was intense in OCP users, both groups were similar
in terms of other baseline variables. The estimated
mean age of menopause for the entire sample was
49.67 ± 3.83 years, ranged 39 to 60 years, while
for OCP users was 49.60 ± 4.33 years and for OCP
non-users was 49.61 ± 3.52 years with no significant
discrepancy. Regarding association between
age at menopause and other characteristics, multivariate
logistic regression analysis shows positive
association between age at menopause with menarche age (Beta=0.125, p=0.012) and last pregnancy age (Beta=0.258, p<0.001). Also, using t test or one-way ANOVA analyses, we could show significant univariate relationships between age at menopause and some baseline variables including mother’s age at menopause (p<0.001), mother and spouse with high educational level (p<0.001), passive cigarette smoking (p<0.001), weekly physical activity (p<0.001), and high family income (p<0.01) (
Baseline characteristics in OCP user and non-user women
Characteristics | OCP user (n = 243) | OCP non-user (n = 157) | P value |
---|---|---|---|
57.24 ± 4.96 | 57.69 ± 5.35 | 0.404 | |
49.60 ± 4.33 | 49.61 ± 3.52 | 0.979 | |
13.60 ± 1.25 | 13.66 ± 1.30 | 0.616 | |
18.23 ± 3.36 | 18.71 ± 3.61 | 0.182 | |
33.28 ± 5.62 | 33.16 ± 5.66 | 0.845 | |
15.75 ± 3.36 | 15.95 ± 3.95 | 0.562 | |
38 (15.6) | 29 (18.5) | 0.459 | |
3.60 ± 0.61 | 3.47 ± 0.70 | 0.611 | |
59 (24.3) | 39 (24.8) | 0.899 | |
211 (86.8) | 132 (84.1) | 0.228 | |
2 (0.8) | 12 (7.6) | < 0.001* | |
7 (2.9) | 10 (6.4) | 0.052 | |
190 (78.2) | 117 (74.5) | 0.397 | |
21 (8.6) | 22 (14.0) | 0.152 | |
48 (19.8) | 35 (22.3) | 0.689 | |
4 (1.6) | 7 (4.5) | 0.074 | |
3 (1.2) | 3 (1.9) | 0.587 | |
105 (43.2) | 55 (35.0) | 0.103 | |
100 (41.2) | 52 (33.1) | 0.005* | |
25 (10.3) | 9 (5.7) | 0.139 | |
7.35 ± 1.88 | 7.21 ± 2.50 | 0.550 | |
*; P<0.05 and OCP; Oral contraceptive pills.
Multivariable linear regression model for identifying the determinants of the age at menopause
Characteristics | P value | Beta | SE |
---|---|---|---|
0.190 | 0.148 | 0.113 | |
0.018* | 0.065 | 0.027 | |
< 0.001* | 3.643 | 0.397 | |
0.263 | 0.320 | 0.285 | |
0.821 | 0.055 | 0.242 | |
< 0.001* | -1.817 | 0.313 | |
< 0.001* | 0.780 | 0.202 | |
0.002* | 0.806 | 0.256 | |
*; P<0.05.
The mean age at menopause was 49.6 ± 4.02 years according to previous studies (
Age at menopause varies across different nations, while is shown a raise in all nations. But, this trend seems paradoxical because existence of several determinants. In this regard, different range of menopausal age and various related determinants have been reported from different countries. In a study by Dratva et al. (
In this study, physical activity, education, mother’s age at menopause, last pregnancy age, income and smoking are found to be related with age at natural menopause. Our findings showed that the postmenopausal women doing intense weekly physical activity, having mother with late menopausal age, having higher monthly income, and experiencing later-age pregnancy are likely to reach menopause later than their contemporaries, while smokers have early menopause. This result would help in the planning of health services in menopause units as a new, important issue in developing countries like Iran. Additionally, these services should be available for all women at menopause age.