Association between menstrual disturbances and habitual use of caffeine

Abstract

Objectives
The main objective of this study was to determine whether there is an association between drinking caffeinated beverages and menstruation among Saudi female students.

Methods
During the 2011 academic year, a cross-sectional study was conducted by administering a questionnaire about menstruation and self-reported habitual use of caffeinated food or drinks to 350 premenopausal women with no known medical disease who were working or studying at the University. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by chi-squared cross-tabulation. All tests were two tailed, and results were considered significant when p < 0.05.

Results
Irregular periods were reported by 140 women (40%), amenorrhoea by 26%, oligomenorrhoea by 20.9%, heavy periods by 13.4% and prolonged periods by 9.7%. Few women (7.7%) reported a previous diagnosis of polycystic ovary disease. Coffee was a risk factor for both prolonged periods (OR, 2.37; 95% CI, 1.09–5.12; p = 0.03) and oligomenorrhoea (1.95; 1.15–3.30; p = 0.014). Nescafe was a risk factor for heavy periods (2.22; 1.91–4.12; p = 0.011) and menstrual symptoms (1.84; 1.06–3.02; p = 0.039). Chocolate was protective against premenstrual symptoms (0.22; 0.06–0.85; p = 0.049).

Conclusions
There is a high prevalence of undiagnosed menstrual disturbances among Saudi university women. Habitual use of caffeine should be considered a risk factor for most menstrual abnormalities.

Full text

Student Article
Association between menstrual disturbances and habitual use
of caffeine
Asmaa Zki Bin Mahmoud
*
, Alaa Naeem Makhdoom, Lujain Alaaldeen Mufti,
Rasha Salem Alreheli, Rawan Ghazi Farghal and Sarah Ehab Aljaouni
College of Medicine, Taibah University, Almadinah Almunawwarah, Kingdom of Saudi Arabia
Received 5 February 2014; revised 15 March 2014; accepted 20 March 2014
ﺍﻝﻡﻝﺥﺹ
ﺃﻩﺩﺍﻑﺍﻝﺏﺡﺙ:ﺕﻩﺩﻑﻩﺫﻩﺍﻝﺩﺭﺍﺱﺓﺇﻝﻯﺕﺡﺩﻱﺩﻉﻝﺍﻕﺓﺵﺭﺏ
ﺍﻝﻡﺵﺭﻭﺏﺍﺕﺍﻝﻡﺡﺕﻭﻱﺓﻉﻝﻯﺍﻝﻙﺍﻑﻱﻱﻥﺏﺍﻝﺡﻱﺽﺏﻱﻥﺍﻝﻁﺍﻝﺏﺍﺕ
ﺍﻝﺱﻉﻭﺩﻱﺍﺕ
.
ﻁﺭﻕﺍﻝﺏﺡﺙ:ﺃﺝﺭﻱﺕﻩﺫﻩﺍﻝﺩﺭﺍﺱﺓﺍﻝﻡﻕﻁﻉﻱﺓﺥﻝﺍﻝﺍﻝﻉﺍﻡﺍﻝﺃﻙﺍﺩﻱﻡﻱ
٢٠١١ﻡ،ﻉﻥﻁﺭﻱﻕﺕﻭﺯﻱﻉﺍﺱﺕﺏﺍﻥﺓﺫﺍﺕﻱﺓﻡﺕﻉﻝﻕﺓﺏﺍﻝﺡﻱﺽ
ﻭﺍﻝﺍﺱﺕﺥﺩﺍﻡﺍﻝ
ﻡﻉﺕﺍﺩﻝﻝﺃﻁﻉﻡﺓﺃﻭﺍﻝﻡﺵﺭﻭﺏﺍﺕﺍﻝﻡﺡﺕﻭﻱﺓﻉﻝﻯ
ﺍﻝﻙﺍﻑﻱﻱﻥ،ﺵﻡﻝﺕ٣٥٠ﺱﻱﺩﺓﻕﺏﻝﺍﻥﻕﻁﺍﻉﺍﻝﺡﻱﺽﻡﻥﻡﻥﺱﻭﺏﺍﺕ
ﺍﻝﺝﺍﻡﻉﺓﺍﻝﻝﺍﺕﻱﻝﺍﻱﻉﺍﻥﻱﻥﻡﻥﺃﻡﺭ
ﺍﺽﻁﺏﻱﺓ.ﺕﻡﺡﺱﺍﺏﻡﻉﺩﻝ
ﺍﻝﺍﺡﺕﻡﺍﻝﺍﺕﻭﻥﻁﺍﻕﺍﻝﺙﻕﺓ٩٥%ﺏﻭﺍﺱﻁﺓﺝﺩﻭﻝﺓﻡﻉﺩﻝﺍﻝﺕﺭﺏﻱﻉ
ﻙﺍﻱ.ﻭﺍﻉﺕﺏﺭﺕﺝﻡﻱﻉﺍﻝﺕﺡﻝﻱﻝﺍﺕﺫﺍﺕﻕﻱﻡﺓﺩﻝﺍﻝﻱﺓﺇﺫﺍ
ﻙﺍﻥﺕﻕﻱﻡﺓ
Pﺃﻙﺏﺭﻡﻥ٠٥٠.
ﺍﻝﻥﺕﺍﺉﺝ:ﺕﺕﻉﻉﺍﺍﻥﻥﻱﻱ١٤٠ﺱﻱﺩﺓ)٤٠%(ﻡﻥﺍﻝﻉﻱﻥﺓﻡﻥﺍﺽﻁﺭﺍﺏﺍﺕﻑﻱ
ﺍﻝﺩﻭﺭﺓﺍﻝﺵﻩﺭﻱﺓ,ﻭ26%ﻡﻥﺍﻥﻕﻁﺍﻉﺍﻝﺡﻱﺽ,ﻭ٢٠.٩%ﻡﻥ
ﻥﺩﺭﺓ
ﺍﻝﺡﻱﺽ,ﻭ١٣.٤%ﻡﻥﻍﺯﺍﺭﺓﺍﻝﺩﻭﺭﺓ,ﻭ9.7%ﻡﻥﻁﻭﻝﻡﺩﺓﺍﻝﺩﻭﺭﺓ.
ﻙﻡﺍﺫﻙﺭﻉﺩﺩﻕﻝﻱﻝ)٧.٧%(ﻡﻥﺍﻝﺱﻱﺩﺍﺕﺃﻥﻝﺩﻱﻩﻥﺕﺵﺥﻱﺹ
ﺱﺍﺏﻕﻝﻡﺭﺽﺍﻝﻡﺏﻱﺽ
ﺍﻝﻡﺕﻉﺩﺩﺍﻝﻙﻱﺱﺍﺕ.ﻭﻭﺝﺩﺃﻥﺍﻝﻕﻩﻭﺓﻉﺍﻡﻝ
ﺥﻁﻭﺭﺓﻝﻙﻝﺍﻡﻥﻁﻭﻝﻡﺩﺓﺍﻝﺩﻭﺭﺓﻭﻥﺩﺭﺓﺍﻝﺡﻱﺽ.ﻙﻡﺍﻭﺝﺩﺃﻥ
ﺍﻝﻥﺱﻙﺍﻑﻱﻩﻉﺍﻡﻝﺥﻁﻭﺭﺓﻝﻍﺯﺍﺭﺓﺍﻝﺩﻭ
ﺭﺓﻭﺃﻉﺭﺍﺽﺍﻝﺡﻱﺽ.ﻭﻭﺝﺩﺃﻥ
ﺍﻝﺵﻭﻙﻭﻝﺍﺕﺓﺕﺡﻡﻱﻡﻥﺃﻉﺭﺍﺽﻡﺕﻝﺍﺯﻡﺓﻡﺍﻕﺏﻝﺍﻝﺡﻱﺽ.
ﺍﻝﺍﺱﺕﻥﺕﺍﺝﺍﺕ:ﻩﻥﺍﻙﺍﺭﺕﻑﺍﻉﻡﻉﺩﻝﺍﺽﻁﺭﺍﺏﺍﺕﺍﻝﺡﻱﺽﻍﻱﺭ
ﺍﻝﻡﺵﺥﺹﺓﺏﻱﻥﺍﻝﺱﻱﺩﺍﺕﺍﻝﺱﻉﻭﺩﻱﺍﺕﻑﻱﺍﻝﺝﺍﻡﻉﺓ.ﻭﺍﻝﺍﺱﺕﺥﺩﺍﻡ
ﺍﻝﻡﻉﺕﺍﺩﻝﻝﻙﺍﻑﻱﻱﻥﻱﺝﺏﺍﻉﺕﺏﺍﺭﻩﻉﺍﻡﻝﺥﻁﻭﺭﺓﻝﻡﻉﻅﻡﺍﺽﻁﺭﺍﺏﺍﺕ
ﺍﻝﺡﻱﺽ.
ﺍﻝ
ﻙﻝﻡﺍﺕﺍﻝﻡﻑﺕﺍﺡﻱﺓ:ﺍﻝﻡﺵﺭﻭﺏﺍﺕﺍﻝﻡﺡﺕﻭﻱﺓﻉﻝﻯﺍﻝﻙﺍﻑﻱﻱﻥ؛ﻉﺩﻡ
ﺍﻥﺕﻅﺍﻡﺍﻝﺡﻱﺽ؛ﻡﺏﻱﺽﻡﺕﻉﺩﺩﺍﻝﻙﻱﺱﺍﺕ؛ﻡﺕﻝﺍﺯﻡﺓﻡﺍﻕﺏﻝ
ﺍﻝﺡﻱﺽ.
Abstract
Objectives: The main objective of this study was to
determine whether there is an association between
drinking caffeinated beverages and menstruation among
Saudi female students.
Methods: During the 2011 academic year, a cross-
sectional study was conducted by administering a ques-
tionnaire about menstruation and self-reported habitual
use of caffeinated food or drinks to 350 premenopausal
women with no known medical disease who were working
or studying at the University. Odds ratios (ORs) and
95% confidence intervals (CIs) were calculated by chi-
squared cross-tabulation. All tests were two tailed, and
results were considered significant when p<0.05.
Results: Irregular periods were reported by 140 women
(40%), amenorrhoea by 26%, oligomenorrhoea by
20.9%, heavy periods by 13.4% and prolonged periods
by 9.7%. Few women (7.7%) reported a previous diag-
nosis of polycystic ovary disease. Coffee was a risk factor
for both prolonged periods (OR, 2.37; 95% CI, 1.09
e5.12; p¼0.03) and oligomenorrhoea (1.95; 1.15e3.30;
p¼0.014). Nescafe was a risk factor for heavy periods
(2.22; 1.91e4.12; p¼0.011) and menstrual symptoms
(1.84; 1.06e3.02; p¼0.039). Chocolate was protective
against premenstrual symptoms (0.22; 0.06e0.85;
p¼0.049).
*Corresponding address: Medical Students at the College of
Medicine, Taibah University, Almadinah Almunawwarah,
Kingdom of Saudi Arabia.
E-mail: asmaazki90@hotmail.com,fullah_zak@hotmail.com
(A.Z. Bin Mahmoud)
Peer review under responsibility of Taibah University.
Production and hosting by Elsevier
Taibah University
Journal of Taibah University Medical Sciences
www.sciencedirect.com
1658-3612 Ó2014 Taibah University. Production and hosting by Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.jtumed.2014.03.012
Journal of Taibah University Medical Sciences (2014) -(-), 1e4
Please cite this article in press as: Bin Mahmoud AZ, et al., Association between menstrual disturbances and habitual use of caffeine, Journal of Taibah
University Medical Sciences (2014), http://dx.doi.org/10.1016/j.jtumed.2014.03.012

Conclusions: There is a high prevalence of undiagnosed
menstrual disturbances among Saudi university women.
Habitual use of caffeine should be considered a risk
factor for most menstrual abnormalities.
Ó2014 Taibah University. Production and hosting by
Elsevier Ltd. All rights reserved.
Introduction
Caffeine is one of the most commonly ingested pharma-
cologically active substances. It is present in coffee, tea, soft
drinks, cocoa, solid milk chocolate and many medications.
Caffeine is rapidly absorbed from the digestive tract and
distributed throughout the tissues. The mechanisms of action
of caffeine include inhibition of hydrolysis of cyclic 3ʹ,5ʹ-
adenosine monophosphate and 3ʹ,5ʹ-guanosine mono-
phosphate
1
and antagonism of adenosine.
2
Therefore,
caffeine may alter hormone profiles and thus affect
menstrual function. Menstrual dysfunction, in turn, may be
related to other health outcomes, such as fertility,
osteoporosis and breast cancer.
3
The results of studies of coffee and caffeinated beverage
consumption in relation to fertility are inconsistent. Several
studies have reported deleterious effects,
4e6
while others have
shown either no association,
7
a relation only at very high
levels of intake
8
or even improved fertility.
9
One study
10
concluded that soft drinks may be a risk factor for
infertility, irrespective of their caffeine content. A possible
explanation for this inconsistency is that most of the studies
were retrospective and thus subject to recall and other types
of bias. Although clear pathophysiological mechanisms for
the presumed effects of caffeine on fertility have not been
elucidated, it has been suggested to affect ovulation. In
contrast, caffeine has been linked to greater sensitivity to
insulin,
11
which in turn has been related to improved
ovulatory function in women with polycystic ovary
disease,
12
which is the commonest cause of anovulation in
women of reproductive age and the commonest cause of
infertility due to ovulation disorders.
13e14
No studies have
been performed on Saudi women, who are high consumers
of caffeinated drinks, especially Arabic coffee.
The aim of this study was to investigate whether there is
an association between menstrual abnormalities and caffeine
consumption among premenopausal Saudi women at Taibah
University.
Material and Methods
This cross-sectional study was conducted by third-year
female medical students during the 2011 academic year at
Taibah University, Almadinah Almunawwarah, Kingdom of
Saudi Arabia after approval from the authorities at the
College of Medicine and as part of their research method-
ology course. An online calculation was used to estimate a
sample size of 384 for a confidence interval (CI) of 95% and a
margin of error of 5%. We therefore prepared 384 pre-coded,
well-constructed questionnaires and placed them at the
reception of the infirmary. The receptionists handed the
questionnaire randomly to 384 women aged 17e45 years
who were working or studying at the University and
attending the infirmary for various causes and asked them to
answer the questions carefully, after obtaining their verbal
consent to participate. The questionnaires were collected at
the end of the day by the researchers for revision and data
entry. Of the 384 questionnaires, 34 were excluded because of
incomplete data or exclusion criteria (currently pregnant;
smoker; using oral contraceptives, an intrauterine device or
hormonal medications; taking medications containing
caffeine; history of hysterectomy, hypothyroidism or any
gynaecological disease except polycystic ovarian disease).
The questionnaire elicited information about educational
level, marital status, premenstrual syndrome, amount of
bleeding (average, heavy or scanty) and the regularity and
duration of periods.
Irregular periods were defined as any type of abnormal
bleeding, including late or early period, bleeding between
periods, missed periods, continuous periods or periods
occurring twice in one cycle. Any period that lasted for more
than 8 days was considered to be long, and one that occurred
every 24 days or fewer was considered to be short. Ame-
norrhoea was defined as the absence of menses for 3 months
in a woman with previously normal menstruation or 9
months in a woman with a history of oligomenorrhoea. One
question asked about diagnoses of polycystic ovarian dis-
ease, and others asked about usual daily consumption of the
caffeinated beverages coffee, tea, Nescafe, carbonated soft
drinks, chocolate and hot chocolate, in number of cups or
cans per day.
Statistical analysis
All data were managed and analysed with SPSS software
for Windows version 17. Prevalence was calculated as per-
centages (frequency), and odds ratios (ORs) were calculated
with their 95% CIs by chi-squared cross-tabulation. All tests
were two-tailed, and results were considered significant when
p<0.05.
Results
Most women (76%) were aged 17e25 years, had a
bachelor’s degree (82.9%) and were single (63.4%) (Table 1).
Regular menstruation was reported by 60%, an average
duration (3e7 days) by 87.7% and an average volume by
81.7%. The prevalence of premenstrual symptoms (68.6%)
exceeded that of menstrual symptoms (18%). Irregular
periods were reported by 40%, with amenorrhoea in 26%,
oligomenorrhoea in 20.9%, heavy periods in 13.4% and
prolonged periods in 9.7%. Few women reported a
previous diagnosis of polycystic ovarian disease (7.7%)
(Table 2).
The commonest source of caffeine use was chocolate
(66.6%). More than half the women drank coffee (52%),
with 32.9% drinking Arabian coffee; followed by tea
(48.9%), with 36.3% drinking red tea; then carbonated soft
drinks (41.6%), with 31.1% drinking Pepsi Cola; and lastly
Nescafe (34.6%), with 17.4% drinking cappuccino and
11.1% drinking Coffee-Mate
Ò
. Most women did not exceed
two cups of any drink daily (46.6% for coffee, 43.7% for tea,
A.Z. Bin Mahmoud et al.2
Please cite this article in press as: Bin Mahmoud AZ, et al., Association between menstrual disturbances and habitual use of caffeine, Journal of Taibah
University Medical Sciences (2014), http://dx.doi.org/10.1016/j.jtumed.2014.03.012

20.6% for Nescafe, 45.1% for soft drinks and 28% for hot
chocolate). Only a few consumed large amounts (>5 cups or
cans daily) of coffee (9.4%), tea (2.3%), soft drinks (1.7%) or
hot chocolate (0.3%) (Table 3).
Coffee was a risk factor for both prolonged periods (OR,
2.37; 95% CI, 1.09e5.12; p¼0.03) and oligomenorrhoea
(1.95; 1.15e3.30; p¼0.014); and Nescafe was a risk factor
for heavy periods (2.22; 1.91e4.12; p¼0.011) and menstrual
symptoms (1.84; 1.06e3.02; p¼0.039). Chocolate was pro-
tective against premenstrual symptoms (0.22; 0.06e0.85;
p¼0.049) (Table 4). No significant risk seen with drinking
tea or carbonated soft drinks (data not shown).
Discussion
Women who consumed caffeine were more likely to have
menstrual abnormalities, mainly prolonged and heavy
menses, as well as oligomenorrhoea. The association with
prolonged or heavy menstruation is biologically unreason-
able, as caffeine is a known vasoconstrictor
15
and would be
expected to reduce uterine blood flow, which would reduce
menstrual bleeding and shorten the duration of menses.
Research in pregnant animals
16
and humans
17
indicates
that caffeine increases uterine vascular resistance and
reduces uterine blood flow. The mechanism by which
caffeine alters the duration of the menstrual cycle is not
clear, but it could occur via an effect on sex hormones or
hormone receptors. Kitts
18
found that constituents of
coffee are weakly oestrogenic. Caffeine inhibits the action
of adenosine, which in laboratory studies affects luteinizing
hormone and follicle-stimulating hormone,
19,20
which
could in turn affect the length of the menstrual cycle.
Gilbert and Rice
21
found depressed oestrogen levels in
female monkeys at a dose of caffeine associated with
miscarriages, stillbirths and decreased maternal weight
gain. Associations were found between caffeine intake and
oestradiol and/or oestrone levels in some studies
22,23
but
not in others.
24
Cooper et al.
24
found no notable relation
between caffeine intake and cycle length, variability or
menses length. Other researchers
4
found no indication that
caffeine intake is related to an increased risk for anovulation.
The difference between our results and those of others
could be due to the presence of confounding factors, as
66.6% of our participants habitually used non-caffeinated
beverages. Methodological differences might also explain
the differences in results. In most other studies, data was not
collected on all drinks, food and drugs containing caffeine,
while we had information on all foods and excluded all
medications containing caffeine in order to minimize their
contribution to total caffeine intake. Still, potential exposure
Table 2: Characteristics of menstrual periods of participants.
Variable No. (%)
Regularity
Regular 210 (60%)
Irregular 140 (40 %)
Duration (days)
<3 7 (2.0%)
3e7 307 (87.7%)
>7 34 (9.7%)
Volume
Moderate 286 (81.7%)
Heavy 47 (13.4%)
Light 17 (4.9%)
Symptoms 63 (18%)
Premenstrual syndrome 240 (68.6%)
Amenorrhoea 91 (26.0%)
Oligomenorrhoea 73 (20.9%)
History of polycystic ovary disease 27 (7.7%)
Table 3: Use of caffeine-containing beverages by participating
women.
Caffeinated food
or drink
No. (%) Amount: No. (%)
Coffee 182 (52%) 1e2 cups: 163 (46.6%)
3e5 cups: 44 (12.6%)
>5 cups: 33 (9.4%)
Nescafe 121 (34.6%) 1e2 cups: 72 (20.6%)
3e5 cups: 2 (0.5%)
>5 cups: 0%
Tea 171 (48.9%) 1e2 cups: 153 (43.7 %)
3e5 cups: 44 (12.6%)
>5 cups: 8 (2.3%)
Carbonated
soft drink
146 (41.6%) 1e2 cans: 123 (35.1%)
3e5 cans: 17 (4.9%)
>5 cans: 6 (1.7%)
Chocolate 233 (66.6%) One piece: 109 (31.1)%
Whole bar: 67 (19.1%)
>bar: 29 (8.3%)
Hot chocolate 105 (30%) 1e2 cups: 98 (28%)
3e5 cups: 6 (1.7%)
>5 cups: 1 (0.3%)
Table 4: Significant odds ratios (ORs) for menstrual abnor-
malities associated with use of caffeine-containing products.
Product Abnormality or symptoms OR 95% CI p
Coffee Prolonged periods 2.37 1.09e5.12 0.03
Oligomenorrhoea 1.95 1.15e3.30 0.014
Nescafe Heavy periods 2.22 1.91e4.12 0.011
Menstrual symptoms 1.84 1.06e3.02 0.039
Chocolate Premenstrual symptoms 0.2 0.05e0.90 0.021
Table 1: Characteristics of participants.
Characteristic No. (%)
Age (years)
17e25 266 (76%)
25e35 52 (14.9%)
35e45 30 (8.6%)
Education
None 0.3%
Primary school 0%
Secondary school 8.9%
Bachelor degree 82.9%
Other 6.6%
Marital status
Single 63.4%
Married 19.7%
Divorced 1.4%
Widowed 13.4%
Separated 1.1%
Association between menstrual disturbances and caffeine intake 3
Please cite this article in press as: Bin Mahmoud AZ, et al., Association between menstrual disturbances and habitual use of caffeine, Journal of Taibah
University Medical Sciences (2014), http://dx.doi.org/10.1016/j.jtumed.2014.03.012

misclassification might have affected our estimates of
caffeine intake. We estimated caffeine dose from a self-
administered questionnaire, and there may be substantial
variation in caffeine content according to serving size, brand,
ingredients, method of beverage preparation and brewing
time.
25,26
Another limitation of our study is its cross-
sectional design, which provides limited capacity to estab-
lish causal relations.
Conclusions
Our study shows that caffeine consumption is related to
prolonged, heavy menses and oligomenorrhoea. Non-
caffeinated drinks, soft drinks and chocolate were not asso-
ciated with abnormal menstruation, and chocolate was
associated with fewer premenstrual symptoms. These find-
ings could have implications for women’s long-term health.
We also found a high prevalence of undiagnosed men-
strual disturbances among Saudi university women.
Habitual use of caffeine-containing products, apart from
chocolate, should be considered a risk factor for most men-
strual abnormalities. Clinical trials should be performed to
confirm these findings and to examine subsequent health
outcomes in women.
Authors’ contributions
All the authors, in association with Zainab Ahmed, con-
structed, distributed and collected the questionnaires and
analysed the data. They wrote the manuscript under the su-
pervision of Dr Intesar Sultan.
Conflict of interest
The authors have no conflict of interest to declare.
Acknowledgements
We thank Zainab Ahmed Dumiati, a fifth-year medical
student at Taibah University for her participation in con-
structing the study, collecting data and writing up the results.
We also thank Dr Intessar Sultan, Professor of Medicine at
the College of Medicine, for her time and help in reviewing
the findings.
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A.Z. Bin Mahmoud et al.4
Please cite this article in press as: Bin Mahmoud AZ, et al., Association between menstrual disturbances and habitual use of caffeine, Journal of Taibah
University Medical Sciences (2014), http://dx.doi.org/10.1016/j.jtumed.2014.03.012