Asian Journal of Medical Sciences 3(8): 151-153, 2011
ISSN: 2040-8773
© Maxwell Scientific Organization, 2011
Received: April 27, 2011
Accepted: July 02, 2011
Published: August 30, 2011
Age at Natural Menopause among Nigerian Women in Zaria, Nigeria
1
L.N. Achie, 1K.V. Olorunshola and 2M. Mabrouk
Department of Human Physiology, Faculty of Medicine,
Ahmadu Bello University, Zaria, Nigeria
2
Department of Human Physiology, Bayero University, Kano, Nigeria
1
Abstract: Menopause and the age of its onset are associated with an increased incidence of cardiovascular
disease and some cancers. The age at natural menopause and some variables (blood pressure, body mass index,
educational level and parity) were investigated by a questionnaire survey of Nigerian women in Zaria. Data was
collected from 88 women aged 40-65 years (mean age 53.59±0.65 years) which included their weight (kg),
height (m) and blood pressure (mmHg) using standard methods. Data was presented as mean±SEM and
frequencies while results were analysed with ANOVA and correlation between variables determined. The mean
and median ages at menopause were 46.16±0.37 and 46.0 years, respectively. A significant positive correlation
(0.263) was found between menopausal age and parity (p<0.05). On the other hand, a negative relationship was
established between menopausal age with diastolic blood pressure (-0.021) and the body mass index (0.041)
which was however not significant (p>0.05). An increase in educational attainment was associated with lower
age at menopause but was not statistically significant. Earlier onset of natural menopause among Nigerian
women in Zaria is strongly associated with parity and inversely associated with body mass index and the
diastolic blood pressure. This study provides some insight into the determinants of age at menopause among
women in Zaria. We recommend longitudinal studies encompassing other variables.
Key words: Blood pressure, body mass index, educational status, natural menopause, menopausal age, Zaria
30% of their lives after menopause. There is a lower
incidence of use of contraception among women in
Northern Nigeria, parity is higher and nutritional status is
also lower. The study was aimed at determining the age
at menopause of Nigerian women in Zaria, a semi-urban
city, as well as some variables associated with its
determinants.
INTRODUCTION
With advancing age, a permanent cessation of
menstruation (menopause) resulting from loss of ovarian
follicular activity occurs. The defining age is between 45
and 55 years (Research on the Menopause, 1981). A
woman’s age at the onset of natural menopause is
associated with several diseases. An early menopause is
associated with an increased risk of osteoporosis and
increased overall mortality while a late menopause is
associated with an increased risk of breast cancer
incidence (Cooper and Sandler, 1998; Kritz-Silverstein,
1993). Associations of disease incidence with menstrual
status lead naturally to the idea that the lifetime risks of
these diseases vary with age at menopause, which has
further increased interest in identifying other factors
associated with age at menopause.
The age at menopause differ in different societies.
Contemporary industrialized populations demonstrate a
later median age at menopause (51.4 years) than
populations that are non-industrialized or poorly
nourished (48.28 years), (Gold et al., 2001; Noreh et al.,
1997). Although the timing of menopause affects longterm disease risk, little is known about factors that affect
this timing. With improvement in life expectancy
globally, more women in developing countries will live
MATERIALS AND METHODS
Study site: The data for the study was collected from
women in Zaria (a cosmopolitan town), Kaduna state.
Zaria is located in Northern Nigeria, latitude 11°3! N,
longitude 7°42! E. The altitude of the area is 610 m and
the annual rainfall is about 1056.6 mm with a mean
annual temperature of 27ºC (Mortimore, 1970).
Study population: A cross-sectional study was carried
out on eighty- eight (88) postmenopausal women in Zaria.
The study was conducted from March, 2009 to October,
2010. Eligible women were identified through multi-stage
sampling of the two local government areas constituting
the town. Two districts each were selected from which 88
women were found eligible. Selection of the volunteers
was based on some inclusion and exclusion criteria. Post
menopausal women included in the study group were at
Corresponding Author: L.N. Achie, Department of Human Physiology, Faculty of Medicine, Ahmadu Bello University, Zaria
151
Asian J. Med. Sci., 3(8): 151-153, 2011
Table 1: Descriptive statistics of age of menopausal women
Parameters
Mean±SEM (n = 88)
Mean age (years) of menopausal women
53.59±0.65
least 1 year amenorrhoeic due to a natural cause without
a hysterectomy or other procedure that would have
stopped their menses (Research on the Menopause, 1981).
The women were between 40-65 years. Women who were
diabetics, hypertensive, who smoke cigarette, drink
alcohol or were on medication were excluded from the
study. The study was undertaken after obtaining consent
from the participants and approval from the Ethical
Committee on Human Research of Ahmadu Bello
University, Zaria.
Mean age at Menopause (years)
46.16±0.37
Median age at menopause
46.00
Depicting the age characteristics of the menopausal women
Series 1
48
47
Age(year)
46.04
Collection of data: A questionnaire was designed
incorporating sociodemographic, obstetric, gynecological
as well as other relevant history. The questionnaires were
self administered from March to September, while the
interviews of the women were conducted in English and
the local dialect of Hausa (a lingua franca in this region).
Using standardized procedures, height (in metres), weight
(in kg) and blood pressure (in mmHg) were measured
using the stadiometer (Harpenden), platform balance
scale, mercury sphygmomanometer (Acosson, A.C.
Cossor & Son (surgical) Ltd., London) and stethoscope
(3M Littmann Classic II S.E. Stethoscope, U.S.A)
respectively. Body Mass Index (BMI) was then calculated
as weight/height2 (kg/m2).
46.25
46.64
46
44.88
45
44.1
44
43
42
NONE
ADULT
EDUCATION
PRIMARY
SECONDARY
TERTIARY
41
EDUCATIONAL STATUS
Fig. 1: A bar chart of the mean age at menopause according to
the educational status
may be brought forward by low socioeconomic status and
malnutrition) in Africans or individuals in developing
countries (Lawlor et al., 2003; Reis et al., 1998). The
resultant effect will be an increased risk in overall
mortality in these women (Cooper and Sandler, 1998).
The age at menopause was lower among highly
educated women (tertiary education, 44.11 years)
compared with those who were not educated (illiterate,
46.64 years), though not significant (Fig. 1). This finding
is consistent with earlier studies which revealed a lower
age at menopause in women with higher education
(Parazzini and Progetto Menopausa Italia Study Group,
2007). Similar studies on the determinants of age at
menopause reveal conflicting findings (Gold et al., 2001;
Hidayet et al., 1999). A low educational level (often
considered one of the best socioeconomic indicators) was
found to be independently associated with a lower age at
natural menopause in their studies. Other researches
reveal that there was no unequivocal evidence of an
association between educational level and age at
menopause from a review of 29 studies (Canavez et al.,
2009).
The body mass index and diastolic blood pressure of
the menopausal women in this study, demonstrated a
negative correlation with menopausal age (Table 2).
However, these relationships were not statistically
significant. On the other hand, and conforming to other
studies, parity (Gold et al., 2001; Parazzini and Progetto
Menopausa Italia Study Group, 2007) was significantly
correlated (positively) with age at natural menopause.
Factors related to the lifetime ofovulatorycyclesare f ound
to be associated with the age at menopause (Palmer et al.,
Statistical analysis: Results were presented as
mean±SEM and frequency distribution, while data was
analysed using Student t-test and one way analysis of
variance (ANOVA). Correlation coefficient was used to
find the relationship between age at natural menopause
(dependent) and different independent variables. Results
were considered statistically significant with p<0.05.
RESULTS AND DISCUSSION
The mean and median age at menopause for the study
population is 46.2 and 46.0 years, respectively (Table 1).
These values are lower than those of previous studies
undertaken to determine these parameters in various
populations in Nigeria. A mean and median age at
menopause of 48.4 and 48.0 years was determined for
women of Yoruba descent (Okonofua et al., 1990). While
a questionnaire survey of women in Abakaliki, southeast
Nigeria revealed a mean and median age of 49.4 and 49
years, respectively (Ozumba et al., 2004). It is established
that there may be ethnic variations to the menopause
experience though some variables (parity, menstrual
cycle) which differ in the different ethnic groups are said
to be the determinants (Neri et al., 1982). The values for
this study were also lower than that in Caucasians; 51.4
years (Gold et al., 2001). Lower values (median age) of
44.0 years was found in an Indian community. An earlier
onset of natural menopause is said to be due to racial,
geographical and lower socioeconomic status (menopause
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Asian J. Med. Sci., 3(8): 151-153, 2011
Table 2: Correlation matrix of age at menopause with some variables
Variables
Parity
BMI
DBP
Menopausal age
0.263**
-0.041
-0.021
Parity
0.025
0.264*
BMI
0.085
DBP
BMI: Body Mass Index; DBP: Diastolic Blood Pressure; *: p<0.05;
**: p<0.01
Hidayet, N.M., S.A. Sharaf, S.R. Aref, T.A. Tawfik and
I.I. Moubarak, 1999. Correlates of age at natural
menopause: A community-based study in Alexandria.
Eastern Mediterranean Health J., 5(2): 307-319.
Kritz-Silverstein, D. and E. Barrett-Connor, 1993. Early
menopause, number of reproductive years, and bone
mineral density in postmenopausal women. Am. J.
Public Health, 83: 983-988.
Lawlor, D.A., S. Ebrahim and G.D. Smith, 2003. The
association of socio-economic position across the life
course and age at menopause: The British women’s
heart and health. Br. J. Obstet. Gynecol., 110(12):
1078-1087.
Mortimore, M.J., 1970. Zaria and its Region: A Nigerian
Savannah City and its Environs. 14th Annual
Conference of the Nigerian Geographical
Association, Department of Geography, Ahmadu
Bello University, Zaria, Nigeria, pp: 41-54.
Neri, A., D. Bider, Y. Lidor and J. Ovadia, 1982.
Menopausal age in various ethnic groups in Isreal.
Maturitas, 4(4): 341-348.
Noreh, J., C. Sekadde-Kigondu, J.G. Karanja and
N.G. Thagana, 1997. Median age at menopause in a
rural, population of Western Kenya. East Afri. Med.
J., 74(10): 634-638.
Okonofua, F.E., A. Lawal and J.K. Bamgbose, 1990.
Features of menopause and menopausal age in
Nigerianwomen. Int. J. Gynecol Obstet., 31(4):
341-345.
Ozumba, B.C., S.N. Obi, E. Obikili and P. Waboso, 2004.
Age, symptoms and perception of menopause among
Nigerian women. Obstet. Gynecol. Ind., 54(6):
575-578.
Palmer, J.R., L. Rosenberg, L.A. Wise, N.J. Horton,
L.L. Adams-Campbell, 2003. Onset of natural
menopause in African American women. Am. J.
Public Health, 93(2): 299-306.
Parazzini, F. and Progetto Menopausa Italia Study Group,
2007. Determinants of age at menopause in women
attending menopause clinics in Italy. Maturitas, 56:
280-287.
Reis, N., T. Pasinlioglu and S. Dane, 1998. The natural
menopause age of women in Erzurum and factors
influencing the age at menopause. Tropic. J. Med.
Sci., 28: 415-418.
Research on the Menopause, 1981. Report of a WHO
Scientific Group, World Health Organization
Technical Report Series, Geneva, 670: 1-120.
2003). Suppression of ovulation by pregnancy or oral
contraceptives results in anovulation, a mechanism
implicated to be associated with a later age at menopause.
CONCLUSION AND RECOMMENDATION
The findings of the present study indicate that women
in Zaria may experience an earlier menopause as
compared to both Caucasians and other Nigerian study
with parity serving as a significant predictor. They thus
are at risk of overall mortality due to early menopause.
Since data is self-reported in a retrospective way,
shortcomings may be encountered especially in those who
had been menopausal for long. We hence recommend a
longitudinal multi-centre study to follow up the natural
history of the Nigerian menopausal transition. Encourage
the establishment of menopause clinics to cater for the
needs of the Nigerian menopausal woman.
ACKNOWLEDGMENT
We would like to thank Messrs. J. Move, J. Timbuak
and Pastor Yusuf of the Faculty of Medicine for their
technical support during the study.
REFERENCES
Canavez, F.S., G.L. Werneck, R.C.M. Parente,
R.K. Celeste and E. Faerstein, 2009. The association
between educational level and age at the menopause:
A systematic review. Arch. Gynecol. Obstet., 283:
83-90. Doi: 10.1007/s0040 4-009-1323-6.
Gold, E.B., J. Bromberger, S. Crawford, S. Samuels,
G.A. Greendale, S.D. Harlow and J. Skurnick, 2001.
Factors associated with age at natural menopause in
a multiethnic sample of midlife women. Am. J.
Epidemiol., 153(9): 865-874.
Cooper, G. and D.F. Sandler, 1998. Ageatnatural
menopause andmortality. Am. J. Epidemiol., 8:
229-235.
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