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Review
Ravindran Jegasothy*, Pallav Sengupta, Sulagna Dutta and Ravichandran Jeganathan
Climate change and declining fertility rate in
Malaysia: the possible connexions
https://doi.org/10.1515/jbcpp-2020-0236
Received July 26, 2020; accepted October 4, 2020;
published online December 14, 2020
Abstract: Climate change is an incessant global phenom-
enon and has turned contentious in the present century.
Malaysia, a developing Asian country, has also undergone
significant vicissitudes in climate, which has been pro-
jected with significant deviations in forthcoming decades.
As per the available studies, climate changes may impact
on the fertility, either via direct effects on the gonadal
functions and neuroendocrine regulations or via several
indirect effects on health, socioeconomic status,
demeaning the quality of food and water. Malaysia is
already observing a declining trend in the Total fertility rate
(TFR) over the past few decades and is currently recorded
below the replacement level of 2.1 which is insufficient to
replace the present population. Moreover, climate changes
reportedly play a role in the emergence and cessation of
various infectious diseases. Besides its immediate effects,
the long-term effects on health and fertility await to be
unveiled. Despite the huge magnitude of the repercussion
of climate changes in Malaysia, research that can explain
the exact cause of the present reduction in fertility pa-
rameters in Malaysia or any measures to preserve the na-
tional population is surprisingly very scarce. Thus, the
present review aims to elucidate the possible missing links
by which climate changes are impairing fertility status in
Malaysia.
Keywords: climate change; fertility; global warming;
infectious disease; pregnancy.
Background
Global climate change is the biggest threat to biodiversity
and is severely affecting natural population of species via
various mechanisms [1, 2]. It has both direct and indirect
impacts on human health as all the physiological adapta-
tion strategies are failing in the face of shifting environ-
mental phenomena [3, 4]. Climate change may directly
affect health by disrupting physiological functions or
indirectly by impairing the overall environmental and
sociodemographic factors indispensable for health, such
as degradation of air and water quality, causing insecurity
of food and shelter etc. [4]. The major climate change is
attained by global warming that induce high risk of disease
outbreaks, sensitive to changes in weather, for example,
cholera, malaria, malnutrition and natural disasters com-
bined [5–7]. Malaysia is also experiencing distubances of
annual rainfall and gradual increase in surface warming,
mainly since the past two decades [8]. Moreover, Malaysia
is also suffering from increasing trends of altered sea level,
surface temperatures, and extreme weather events [8, 9].
Therefore, changes in climate and their consequences
should be paid research attentions.
The long-term effects of climate change on health and
fertility of a population often get ignored while several
factors independently or in combinations, are silently
declining the overall fertility rate in Malaysia. Malaysia has
observed a declining trend in the Total fertility rate (TFR)
over the last three decades. In women, within the age range
of 15–49 years, TFR is showing a decline from 4.9 babies
per woman in 1970 to 1.8 babies in 2018 [10].
Considering high importance of reproductive health in
persistence of a nation’s population, it is crucial in the
present scenario to apprehend how climate change is
affecting fertility parameters. This article is the first ever
published review to present the possible impacts of climate
changes in Malaysia over the fertility parameters. The article
has individually addressed the most essential factors
*Corresponding author: Professor Dato’Dr. Ravindran Jegasothy
Adjunct Professor, Department of Obstetrics & Gynaecology, and
Former Dean, Faculty of Medicine, Bioscience and Nursing, MAHSA
University, Kuala Lumpur, Malaysia, Phone: +6012 610 7997,
E-mail: rjegasothy@yahoo.com
Pallav Sengupta, Department of Physiology, Faculty of Medicine,
Bioscience and Nursing, MAHSA University, Kuala Lumpur, Malaysia.
https://orcid.org/0000-0002-1928-5048
Sulagna Dutta, Department of Oral Biology & Biomedical Sciences,
Faculty of Dentistry, MAHSA University, Kuala Lumpur, Malaysia.
https://orcid.org/0000-0002-7893-5282
Ravichandran Jeganathan, Department of Obstetrics & Gynaecology,
Hospital Sultanah Aminah, Johor Bahru, Malaysia
J Basic Clin Physiol Pharmacol 2020; ▪▪▪(▪▪▪): 20200236
associated with climate change and carved out the possible
pathways by which they may affect male and female
reproduction. It provides a predictive outlook of the extent
to which climate changes can modulate fertility status in
Malaysia and aid preventive measures to be taken with
adequate perception of the magnitude of this scenario.
Fertility status of Malaysia: current
scenario
Malaysia is suffering from a gradual decline in fertility rate
most prominently over the past 30 years. This is evidenced
from the report depicting a reduction in TFR in Malaysia
from 4.9 babies in 1970 to 1.8 babies in 2018 (per woman
within the reproductive age) [10]. In fact, since 2013, the
recorded national TFR is below the replacement level of 2.1
which is definitely alarming. This suggests that the average
number of babies born per woman in the country do not
suffice the number required to replace herself and her
partner in the population [10]. The number of live births
was 501,945 in 2018, a decrease of 1.3 percent as compared
to 508,685 in 2017. The crude birth rate (CBR) declined from
15.9 (2017) to 15.5 (2018) per 1,000 population [10]. To
regulate the long-term effects of climate change on a
population, the nation urgently needs strong predictive
models that can effectively unveil the current impacts on
the fertility status in both men and women as well as
project future scenario of climate-change-mediated fertility
modulations.
Malaysian government demographic reports of 2016
show the distribution of Malaysian population in the
country with 80% living in Peninsular Malaysia, 11% in
Sabah, while only 9% in Sarawak. Distribution of popula-
tion according to ethnicity shows that population in
Peninsular Malaysia bears about 61.8% Malays, 21.4%
Chinese and 6.4% Indians and others make up the rest
0.9% [11].
Even before the implementation of the National Family
Planning Program in 1966, fertility transformation in
Peninsular Malaysia had already started. In 1960, Indians
had 7.3 babies per woman, the highest TFR, followed by
Chinese (6.3) and Malay (5.8) [12]. However, the trend of
TFR among the ethnic groups in Malaysia changed over
time with Malays having highest fertility rate followed by
the Chinese and then Indians since 1965. In Malaysia, the
TFR declined from 5.7, in 1965, to 3.6, between 1966 and
1985, the TFR in Peninsular Malaysia declined from 5.7, in
1965, to 3.6, in 1985, and this was associated with high
increase in use of contraceptive or the contraceptive
prevalence rate (CPR) from 8 to 50%. CPR determines the
proportion of married women using some form of contra-
ception. CPR is defined as ‘the percentage of currently
married women using any contraceptive method’[13]. The
prevalence of contraception stagnated over the next two
decades and even decreased, but the overall fertility rate
decreased significantly through 3.0 in 2000, 2.5 in 2005 and
further decreased to 2.3 in 2008.
The predicted TFR in Peninsular Malaysia, which is
adequate to replace the current population, would be 3.8,
based on the regression equation (TFR=7.27–0.07 CPR)
from a study by Tsui (2001). The observed TFR of 1.8 in 2018
is below the expected value by 2.0, given a moderate CPR of
about 50% [13]. Such statistics pose a threat as Malaysia
becomes an ageing nation with increased elderly popula-
tion by 2030, with circumstances the increasing costs of
health care and reduced youth force. As for the discrep-
ancies in the association of TFR with CPR, it is reported for
various other countries as well [14, 15]. However, the lower
than anticipated TFR has led to speculation that abortion
and sterility are on the rise, along with increasing concern
in understanding the reasons for this phenomenon.
Based on the statistics given by the Department of
Statistics, Malaysia, in 1957, Chinese population contrib-
uted to 37.4% of the whole Malaysian population with TFR
of 7.4 which declined to about 1.1 in 2018. The Malay and
Indian population in Malaysia are facing similar drop in
their TFR from 6.1 in 1957 to 2.4 in 2018 for Malay, and 8.0 in
1957 to 1.25 in 2018 for Indians. The overall TFR of Malay-
sian population declined from 2.1 in 2014, to 2.0 in 2015 and
1.8 in 2018 in women aged between 15 and 49 (Figure 1)
[16, 17]. Previous couple of studies in Malaysia had put
forth links among the socioeconomic factors, ethnicity and
fertility rate [18, 19]. While intermediate variables are
important to explain differences and reduction in fertility
status in Malaysia, there is a serious lack of research on the
subject.
How climate change may impact
fertility?
To date, multiple studies have reported that ‘climate
change is the greatest threat to global health in the 21st
century’[20, 21]. Climate change poses an urgent and sig-
nificant risk to human health and human survival world-
wide. Everyone is at danger, whether affected via
heatwaves, severe weather events, drought, starvation,
altered illnesses and water pollution leading to diarrhoea,
hunger, mass migration or any subsequent issues [22].
2Jegasothy et al.: Climate change and fertility in Malaysia
Developing countries are likely to be most heavily affected
by climate change, with women bearing the greatest toll.
In Malaysia, very little work has been done on pro-
jecting potential impacts of climate change on health
burdens. Climate change affects human health through a
range of direct or indirect exposures. In tandem with
obvious and visible extreme events of floods, forest fires
and heat waves, there exist certain silent factors like global
warming having chronic effects on health and fertility [23].
The reproductive tissues function only within a range of
temperature. Thus, when the ambient temperature exceeds
that critical temperature, it adversely affects reproductive
functions via common mechanisms of gonadal heat shock,
oxidative stress (OS) and alterations in endocrine milieu.
Heat stress can be an environmental as well as an occu-
pational hazard that can lead to chronic illnesses and even
death, from the after effects of heat stroke [24, 25]. Besides
temperature changes, accumulation of toxic contaminants
in air also contribute to various reproductive disorders and
can also induce OS. These environmental cues can induce
unregulated production of free radicals, reactive oxygen
species (ROS) and reactive nitrogen species (RNS). The
chain of oxidative damage severely affects gonadal func-
tions such as impairment of gametogenesis, gamete chro-
matin integrity, mitochondrial functions as well as
increased germ cell apoptosis. This leads to decreased
semen quality in men and reduced oocyte quality and
uterine receptivity in females. The disruption in the hypo-
thalamic–pituitary–gonadal (HPG) axis alter the release of
gonadotropin releasing hormone (GnRH) and subsequent
tropic hormones, luteinizing hormone (LH) and follicle
stimulating hormone (FSH), thereby leading to decreased
testosterone levels in males, oestrogenic and progesterone
in females, impairing gonadal functions (Figure 2). Natural
calamities like storms, floods, draught and changes in
rainfall pattern can affect socioeconomic status of a nation
inflicting malnutrition, poor sanitation, increased food and
water-borne diseases, emergence and spread of infectious
diseases affecting overall health and thereby indirectly
posing threat to fertility.
Climate change in Malaysia and its
impacts on fertility
Temperature change and reproductive
health
Climate change adversely affects global thermal environ-
ment and will continue to increase local temperature as
well as frequency of heat waves [26]. The set-point tem-
perature in humans is 37 °C and potentially lethal effects
associated with hyperthermia are usual at body tempera-
tures above 40–41 °C [27]. Regulation of core body tem-
perature is, therefore, not surprisingly a priority over
several other physiological functions.
In Malaysia, the approximate rate of increase in mean
temperature has been reported to be 0.25 °C per decade in
the peninsular Malaysia, 0.20 °C per decade in Sabah and
0.14 °C per decade in Sarawak [28]. The high spikes in
ambient temperature in 1972, 1972, 1991, 1997–1998 and
2015–2016 were suggested owing to El Nino which was
probably the strongest in the 2015–2016 [8]. Intergovern-
mental Panel on Climate Change (IPCC) had reported that
global mean surface temperature has increased 0.74 °C
between 1905 and 2005 and predicts an increase of 2–4.5 °C
over the next 100 years. In Malaysia, surface temperature of
last four decades has increased between 2.7 and 4.0 °C per
century [29]. Tang (2019) has reported that the yearly
moving average of mean daily temperature shows an up-
trend in different parts of Malaysia, including, Kota Kin-
abalu, Kuching, Malacca, Kuantan and Subang Jaya.
Increase in the annual moving average of mean daily
temperature, was shown to be lowest in magnitude for
Kuching, followed by slightly higher in Kota Kinabalu,
Malacca, Kuantan and Subang Jaya [8]. The information
here is in line with the reports put forth by the Malaysian
Meteorological Department (2009) which also depicted
that Kuching has the least rise in temperature owing to its
slower development pace [30].
There is available literature that emphasizes the impact
of environmental temperature on the viability of a popula-
tion. The lethal limit of temperature is termed as the “critical
thermal limit”(CTL). But a sublethal level of ambient
Figure 1: Declining trend of Malaysian total fertility rate (TFR) based
on ethnicity
TFR of Malaysian population presented in “grey”bars; TFR of Malay,
Chinese and Indian ethnicities are denoted in “green”,“red”and
“blue”, respectively.
Jegasothy et al.: Climate change and fertility in Malaysia 3
temperature can impair the reproductive functions rendering
a population with compromised fecundity [31].
Temperature change and male reproductive
functions
Reproductive functions in both the genders are immensely
affected by temperature changes [32]. Data on the alter-
ations in Malaysian men reproductive functions due to
temperature changes are not available. However, studies
on animal shows that high ambient temperature impairs
spermatogenesis, effects the quality of sperm, leads to
abnormal sperm morphology and reduces sperm motility
[33, 34]. In most of the animals including human, testes are
suspended outside the body cavity in a scrotum such that
the intratesticular temperature is much lower than the core
body temperature. In the testis, there is a complex ther-
moregulatory mechanism that is mediated by counter-
current heat exchange between blood with higher
temperature that enters testes and the ones with lower
temperature exiting testes via the pampiniform plexus [35].
Therefore, the scrotum is so built because of the need for
low temperatures for either spermatogenesis, sperm stor-
age or for reducing mutations in gamete DNA [36]. An in-
crease in testicular temperature in mammals with external
testes result in decreased sperm production, decreased
sperm motility and increased morphologically abnormal
sperm in the ejaculate [35]. Two muscles further monitor
this degree of cooling: the scrotum’s tunica dartos that
Figure 2: Overview of the impact of climate
changes on male and female reproductive
functions
ROS, reactive oxygen species; GnRH,
gonadotropin releasing hormone; LH,
luteinizing hormone; FSH, follicle
stimulating hormone; HPG axis,
hypothalamic-pituitary gonadal axis; E2,
oestradiol.
4Jegasothy et al.: Climate change and fertility in Malaysia
regulate the area of the scrotum and the muscle of the
cremaster that regulates the location of the scrotum
compared with the body. The testicular cells that are
reportedly most vulnerable to get damaged by increase in
ambient temperature are primary spermatocytes and early
spermatids, but effects on spermatogonia and Sertoli cells
have also been observed [37]. Among the major causes of
thermal damage to sperm, oxidative stress (OS) plays a
pivotal role inducing lipid peroxidation of sperm mem-
brane, apoptosis of germ cells, disruption of mitochondrial
functions as well as sperm chromatin disintegration by
DNA fragmentation [38–44].
The developmental competency of the resulting em-
bryo can also be impaired if the fertilization is attained via
spermatozoon affected by heat stress [45]. These include
epigenetic alterations in embryonic development. A recent
study reported the effects of increased environmental
temperature on sperm quality and embryo development in
Holstein bulls. It has showed reduced rates of blastocyst
formation on insemination sperm exposed to high tem-
perature [46].
In another context, it is significant to put forth that
Malaysia is a highly epidemic region for dengue, malaria,
chikungunya and other vector borne diseases [47–49]. It is
reported that prevalence of these diseases increases with
increased ambient temperature [50]. Thus, an indirect pre-
diction can be made on these infection-induced alterations
in semen quality and male fertility status. Reports have
shown the effects of various microorganisms on semen
quality deterioration and altered male fertility [42, 51–54].
Though, studies reporting direct relations of these infection-
induced male sub- or infertility in Malaysian peninsula are
scanty, this could be presumed that these may impact
significantly in reproductive health of Malaysian men.
Temperature change in female reproduction
and pregnancy outcomes
As discussed earlier, overall TFR of Malaysia is declining in
a significant rate and is below the replacement level of 2.1
(1.8 in 2018) implying that offspring produced by each
women in reproductive age do not suffice the number
required to replace herself and her male counterpart in the
Malaysian population [10]. Both male and female factors
contribute to this decline in fertility rate. Amongst various
factors affecting fertility parameters, ambient temperature
changes do play critical role [55]. The ovarian follicle pool
and the enclosed oocytes are very susceptible to hyper-
thermia among the components of the female reproductive
tract. Heat-induced changes within small antral follicles
can later be expressed as impaired maturation and devel-
opmental capabilities of the ovulating oocyte [56]. The
recent climate changes and exposure to elevated ambient
temperatures are curbing normal oogenesis, menstrual
cycle, impregnation rates, pregnancy outcomes as well as
offspring development [35, 55, 57]. Heat stress can disrupt
the production and function of the oocyte for female
gametes. The ability of oocyte to get fertilized and grow in
lactating cows has been shown to deteriorate during the
periods of the year in conjunct with heat stress [58]. There is
plenty of evidence that heat stress can affect the oocyte and
follicle encasing it [59].
Extreme ambient temperatures also affect embryonic
development. Study on cow model shows that hyperther-
mia at day-1 of pregnancy impairs early embryonic devel-
opment. In mice, high ambient temperatures for one day
following mating disrupted normal embryonic develop-
ment [60]. Elevated temperatures during mid-gestation
also reduced foetal weights [61]. An animal study con-
ducted by Hamid et al. (2012) in Universiti Putra Malaysia
has reported the effects of elevated ambient temperature
on reproductive outcomes during different stages of preg-
nancy and the prenatal heat stress on offspring growth.
They have reported from that exposure to elevated ambient
temperature during pre- and peri-implantation has stron-
ger adverse effects on reproductive outcomes and offspring
growth than post-implantation exposure [55].
Temperature and reproductive hormones
Reproductive hormones and their crosstalk with other
hormones intricately regulate the male and female repro-
ductive functions. Few studies are available, although
none from Malaysia, on the effects of elevated environ-
mental temperature on the secretion of reproductive hor-
mones. Initially studies performed in bulls and boars have
put forth that heat stress leads to an initial reduction in the
levels of testosterone concentrations [62, 63]. Recent
studies have shown that extreme heat can lead to
compromised levels of luteinizing hormone, follicle-
stimulating hormone besides diminished levels of testos-
terone. These in turn cause damage to the spermatogenic
cell lineage, reduced semen quality and sperm DNA frag-
mentation in males [64, 65]. In females, the reproductive
hormones are associated intricately with endogenous
temperature regulation of the autonomic nervous system,
such that, oestradiol and progesterone have both central
and peripheral influence on thermoregulation, where
oestradiol is used to facilitate heat dissipation and pro-
gesterone mediates heat storage and increased body
Jegasothy et al.: Climate change and fertility in Malaysia 5
temperatures [66]. High ambient temperature affects the
secretion of both gonadotropins (LH and FSH) and
gonadotrophin-releasing hormone (GnRH) which disrupt
development and maturation of oocyte, early embryonic
development, fetal and placental growth as well as lacta-
tion. Such deleterious effects of heat stress are either the
result of heat stress hyperthermia or the physiological
changes made to regulate body temperature by heat-
stressed animals [35].
Thus, we need effective research on the effects of
ambient temperature changes on Malaysian population
with particular emphasis to exposure-time adversely
affecting male and female fertility.
Haze, air pollution and its impact on
fertility
Episodes of haze in Southeast Asia in 1983, 1984, 1991, 1994
and 1997 caught the attention of the environmental man-
agement of Malaysia and began to enhance awareness of
air pollution owing to climate change [67]. This followed
the establishment of Malaysian Air Quality Guidelines, the
Air Pollution Index, and the Haze Action Plan to improve
air quality [67]. The predominant air pollutants in Malaysia
include carbon monoxide (CO), sulphur dioxide (SO
2
), ni-
trogen dioxide (NO
2
), ozone (O
3
) and Suspended Particu-
late Matter (SPM). Several big cities in Malaysia also
possess high levels of CO, O
x
,SO
2
and Pb [67]. A very
concerning factor for diminished air quality in Malaysia is
the frequent high amounts of smoke and haze that drift into
Malaysia for the past 40 years, caused by the uncontrolled
fires across Indonesia. The haze negatively correlates with
human health, climate and economy [68]. Reports from a
wildlife rescue centre in Borneo on orangutans depicted
that haze results in respiratory tract infection, dehydration,
malnourishment and it is predicted that the long-term ef-
fects can lead to birth defects and reproductive failure. A
recent study by Tajudin et al. (2019) on the health effects of
air pollution of Kuala Lumpur city has reported that
exposure to air pollutants and trace gases can lead to both
immediate and delayed effects on cardiovascular, respi-
ratory and other health issues. Not adequate number of
studies are available that depicted the impact of air
pollution upon health of Malaysian population, thereby
making it arduous to postulate the impact of air pollution
over reproductive health in Malaysia [69]. However, there
are few studies that can be mentioned, such as the one
analysing the health impact of the forest fire of 1997.
Another study had showed that at the peak time of smoke
haze, there is many fold increase in outpatients mainly
suffering from respiratory diseases, in the hospitals of
Sarawak, Kuching as well as in the Kuala Lumpur General
Hospital [70]. There is also evidence of air-pollution
madiated increased cases of acute respiratory infection,
conjuctivitis and asthma, in hospitals in Kuala Lumpur,
between August–September, 1997 [71].
It is high time to generate extensive evidences on the
actual impacts of haze of reproductive health of Malaysian
population that is crucial for population persistence.
Female reproductive system has a unique way to
respond to toxic exposure, particularly towards the pol-
lutants with oestrogenic potential [72] such as, polycyclic
aromatic hydrocarbons, which mimic natural hormone
activities and varying regulation and function of the endo-
crine system [73]. Impacts of air pollutants on reproductive
health often result from short-term exposure during the
vulnerable phases of ovulation or foetal organogenesis. Ef-
fects of certain toxicants can remain hidden for years due to
accumulation in parental tissues and later may be during
pregnancy, lactation or even post-natal development [74]. It
is shown that particulate matter of size less than 10 μmcan
affect pregnant women mainly at the first trimester of preg-
nancy and affect pregnancy duration, impaired foetal growth
as well as negative or undesired pregnancy outcome [75]. The
knowledge about mechanisms of these phenomena is
limited. Menstrual disturbances, most prominently luteal
phase shortening, have been documented as a common
health hazard from fossil fuel combustion [76].
In terms of sperm production, motility and/or
morphology, numerous animal- and human-based
research on exposure to environmental toxins indicate a
negative impact on the semen quality [77–79]. Such toxins
can have oestrogenic and/or anti-androgenic effects,
which in turn modify the hypothalamic–pituitary–gonadal
(HPG) axis, trigger damage to sperm DNA or cause epige-
netic changes in sperms [80–82].
Heavy rainfall, flood and its impact
on fertility
Heavy rain and runoff may contribute to surface water
pollution and may again endanger the supply of clean
water. After floods, the risk of disease outbreaks such as
hepatitis-E, gastrointestinal disease and leptospirosis was
found to increase, particularly in areas with poor hygiene
and displaced populations [83]. Malaysia has witnessed
several major floods in the last two decades [8, 84–88]
(Table 1).
6Jegasothy et al.: Climate change and fertility in Malaysia
There is no direct Malaysian report elucidating the
impact of flood and water quality on male and female
reproductive health. However, flood causes decreased
water quality [89], which affects reproductive health in
both [90]. Floods can affect the health of new-borns by
affecting the pregnanat women in terms of both mental
and physical health and diminishing their capability to
avail health services. Studies of women with prenatal
disaster exposure have revealed that high levels of pre-
natal stress positively correlate with poor pregnancy
outcomes [91] and poor health outcomes in offspring, that
include their behavioural and psychiatric features [92].
The risk of adverse effects on birth outcomes and child’s
health increase with magnitude and duration of disaster
exposure within the gestational period [83]. Floods and
changes in rainfall pattern severely creek into socioeco-
nomic status of the population inflicting malnutrition,
poor sanitation, food- and water-borne infectious dis-
eases, which individually or as combined factors exert
their toll on fertility.
Climate change, infectious
diseases and infertility
Increasing global temperatures will shorten the length of
winter, facilitating potential disease-carrying agents and
aid further spread of diseases [6]. Climate change may
render the habitats unsuited for animals, compelling them
to migrate more to urban areas and thus enhancing the risk
of transmission of zoonotic diseases [6]. The World Health
Organization (WHO) warned in 2007 that emerging infec-
tious diseases are becoming a growing threat in the face of
increasing urbanization, resistance to antimicrobials and
climate change [93].
Dengue is a prevalent disease in Malaysia. It was
projected that climate changes have great influence over
the dengue prevalence in Malaysia [94]. The influence of
climate change on monsoon seasons bring about variation
in transmission of dengue in Malaysia [50, 94]. Institute for
Medical Research (IMR) model depicted that high rainfall
leads to higher dengue transmission. The vector-borne
diseases, mainly dengue and malaria also increase with
temperature fluctuations due to increased availability of
the vector breeding habitats. For example, between
January 1 and August 20, 2016, a total of 71,590 dengue
cases were reported in Malaysia with 162 deaths. The bulk
of the cases were in the states of Selangor, Kelantan, Johor
and Kuala Lumpur. Climate change would have a direct
effect on vector distribution and consequently in diseases,
Table :Major floods and other extreme weather events in past two
decades in Malaysia.
Occurrence Description and consequences
December Tropical Storm Vamei was a tropical Pacific
cyclone developed closer to the equator than
any other tropical cyclone. Vamei (also known
as the Typhoon Vamei) originated in the
South China Sea at .°Non December as
the last storm in during the Pacific
typhoon season. This was called as a typhoon
as it had sustained wind speed of km/h
( mph) and appeared like an eye. It caused
landslides and severe flooding in eastern
Peninsular Malaysia, with five deaths and a
huge economic damage of $.million
().
December –
January
Typhoon Utor passed across the central
Philippines in December , while its re-
sidual moisture indirectly led to immense
flooding in Malaysia. This series of floods
affected the region for a long duration till it
ceased in February []. The tropical
moisture together with high velocity monsoon
winds continued to persistent precipitation
over Malaysia, especially the states of Johor,
Pahang and Malacca. Peak rainfall of
.mm (. in) was recorded in Bandar
Muadzam Shah with almost similar records in
surrounding region, over a four-day period of
the rainfall spree []. Segamat and Kota
Tinggi were adversely affected by the floods
and turned inaccessible by land. There were
eight deaths recorded from this historical
flooding.
October–November
A devastating flood series was observed in
Thailand and Malaysia in , due to
abnormal late arrival of monsoon moisture
over the Bay of Bengal. This development led
to overflow of Chao Phraya, the meeting zone
of rivers and affected Bangkok, and subse-
quently after two weeks, it induced a tropical
depression in the further south causing
floods in Malaysian states of Kedah and Per-
lis. These flash floods severely affected
health, food supply, education sectors,
transportation and overall economy in
Malaysia. This contaminated water supply in
Kedah and Perlis, which compelled these
states to thrive on water supplies from the
neighbouring Perak state. As per the reports
from the federal government, the floods
damaged over , ha of rice fields in
Kedah alone, for which the government
pledged a compensation of million ringgit
to the farmers []. Almost , people
were evacuated, and four deaths were recor-
ded as the consequence of this flood series
[].
Jegasothy et al.: Climate change and fertility in Malaysia 7
such as, dengue, malaria, filariasis and Japanese en-
cephalitis (JE) as well [5, 48]. Food and water-borne dis-
eases also are predominant in tropical and subtropical
countries which may be the indirect health impacts of
climate change. These include: (i) diarrhoeal diseases
caused by a variety of organisms (such as, Escherichia
coli,Vibrio cholera, salmonellae and viruses), (ii) other
viral diseases (such as, hepatitis A and poliomyelitis) and
(iii) protozoan diseases (such as giardiasis and amoebic
dysentery) [29].
Dengue may significantly contribute in impairment of
reproductive parameters [95, 96]. A single centred study
was conducted to analyse the patterns and outcomes of
dengue infection amongst pregnant women in Malaysia. It
suggested that dengue infection during pregnancy may
result in maternal morbidity and death, particularly in
Table :(continued)
Occurrence Description and consequences
January–February
Various regions of Sabah including Mengga-
tal, Penampang and Tuaran were flooded due
to heavy rainfall and flash flooding. As of
February , more than , people had
been evacuated to relief centres in Beau-
fort and Tenom. There were two reported
deaths and property damage scored to mil-
lions of ringgits [].
October–November
The Peninsular Malaysia tornado outbreak of
is a natural phenomenon that took
place in the state of Kedah and Selangor,
Malaysia from October to November
. Kedah and Selangor were hit by epi-
sodes of EFtornado, each lasting for –
min with wind speed up to km/h. The
frequent tornado formation was speculated to
have been due to changes in monsoon. This
calamity rendered , homeless (,
homes destroyed) and economic damage of
about $.billion (USD) (as per the currency
rate of the time in ).
December –
January
The series of floods in affected most of the
Southeast Asian countries and reportedly
caused by the northeast monsoon, affecting
more than , people and at least
reported deaths. Malaysian East Coast were
severely affected by the flooding, the regions
included Pahang, Terengganu and Kelantan
states. Moreover, states in Peninsular
Malaysia including Johor, Perak, Selangor
and Perlis and a state in East Malaysia, Sabah
also experienced the floods due to the heavy
rainfalls with peak of mm. These floods
have been described as the most severe
floods in past few decades [].
January–February
Heavy intensity rainfall from January
till the end of February, led to flooding across
the Eastern Malaysia, mainly in Sarawak and
Sabah. The number of evacuated people were
estimated to be around , people, with
property damage of almost $. billion
(USD) and one casualty of a teenage girl was
reported, a teenage girl [].
February–March Heavy rainfall occurring in the first half of
February , led to immense flood in
Malaysian states including Bau, Samarahan
and Serian in Sarawak, Tangkak, Ledang and
Segamat in Johor and Alor Gajah, Central
Malacca and Jasin in Malacca and parts of
Negeri Sembilan. Three casualties were re-
ported, and property damage were estimated
to be $ million (USD) [].
December –early
Flooding that occurred in southern Thailand
had significant effects on Malaysian states of
Kelantan and Terengganu. Changes in the
annual monsoon season was the major cause
Table :(continued)
Occurrence Description and consequences
of this flood and led to an estimated loss of
USD billion, contributing to severe damage
in agriculture, infrastructure and tourism [].
October Typhoon Paolo, originated from a tropical
cyclone, stroked across Sabah. It was char-
acterised by strong wind and heavy rain. It
had dreadful consequence rendering
deaths, more than missing cases and
about , people became homeless [].
November A sudden flood in Penang lead to evacuation
of approximately people. The calamity
was accompanied by strong winds and long
duration torrential rain and was reportedly
developed from tropical cyclone. This calam-
ity resulted in at least deaths and over
, after floods swept through the
northern states of Penang and Kedah in
peninsular Malaysia [].
December Strong wind blew across the west coast of
Sarawak, Sabah and Labuan at – km/h
and was caused by Tropical Storm Kai-Tak
that originated in the Western Pacific Ocean
[].
Jan The annual northeast monsoon caused high
intensity rainfall that led to floods in Malaysia
particularly in the states of Terengganu,
Johor, Pahang and Sabah. The flood killed two
in Pahang and caused about , people to
be displaced nationwide. Kuantan and Rom-
pin districts in Pahang were the most affected
regions. Malaysia’s National Disaster Man-
agement Agency (NDMA) reported that relief
centres were set in two districts, which shel-
tered more than , displaced people [].
8Jegasothy et al.: Climate change and fertility in Malaysia
premature baby delivery. In the case of febrile pregnant
women, dengue infection should be strongly suspected
[95].
The recently emerged novel coronavirus, SARS-CoV-2
causing the disease COVID-19, has raised waves of fear
across the globe and Malaysia is one of the countries
moderately affected by the same. A correlation between
metrological parameters and COVID-19 cases has already
been reported [97]. As reported till 23 July 2020, a total of
15.1 million people around the world have been infected
with COVID-19 since the coronavirus outbreak began over a
couple of months ago. The Ministry of Health (MoH) of
Malaysia has confirmed that COVID-19 cases in Malaysia
have increased to 8,831 (as per reports on 23 July 2020) [98].
This is not the first time in recent history that the world has
struggled with a global epidemic—there was the severe
acute respiratory syndrome (SARS) in 2003, the Middle East
coronavirus respiratory syndrome (MERS) first identified in
2012 and the Zika virus in 2015–2016—and this coronavirus
is unlikely to be the last [50]. However, unlike coronavirus
infections in pregnant women caused by SARS and MERS,
COVID-19 have not yet posed threat to maternal survival. At
this point in the global pandemic of COVID-19 infection,
there is no evidence that SARS-CoV-2 undergoes intra-
uterine or transplacental transmission from infected
pregnant women to their foetus. A very recent study has
suggested that the SARS-CoV-2 might directly bind to re-
ceptors in the reproductive tissues of patients [99] and may
impair gonadal functions. The study encourages long-term
interventions and follow up over the COVID-19 affected
men, to unveil the exact effects of this virus on male fertility
[99–103].
Climate changes, socioeconomic
and demographic factors and
infertility
Malaysia is a fast-growing developing country. So, there
are scopes of regular shifts in economic variables that
would impact food security. There is a wide range of eco-
nomic channels through which climate change can affect
fertility rate of a nation, that includes sectoral reallocation,
wage inequalities among gender, longevity and child
mortality [104]. Through its economic effects, climate
change could have a substantial impact on population
growth, primarily by influencing behaviour of people to-
wards increasing family size. It influences their decision on
whether to devote more time and money for child-rearing,
or channelize those to have more children [104]. The cross-
relations among climate change-sociodemographic fac-
tors-infertility are subject for detailed interventions at
different strata in Malaysian population which is presently
lacking. However, a recent study on 300 men attending the
Fertility Clinic, International Islamic University Malaysia
(IIUM), demonstrated significant associations between
critical sociodemographic factors, such as household in-
come, educational attainment and others, with levels of
seminal abnormalities in the subjects [105].
The climate conditions in Malaysia are evolving very
rapidly and have had adverse effects on food production
[106]. Even that, food insecurity in households is not only
related to social and economic factors, but also linked
significantly to the direct and indirect effects of climate
factors [107]. Previous studies have shown that 50% or
more of the rural low-income households face certain food
insecurity. A recent study showed that 23.3% of poor and
low-income households are poorly food-insecure, 14.3%
are moderately food-insecure and 9.6% are seriously food-
insecure in Malaysia [108]. The global food supply system
faces serious new threats from economic and related crises
and climate change, which have a direct effect on poor
people’s nutritional well-being by reducing their access to
nutritious food. In deal with this, vulnerable populations
prefer calorie-rich, but nutrient-poor, food consumption.
The consequence is a decrease in dietary quality and ul-
timately in quantity, rising micronutrient malnutrition
(or secret hunger) and exacerbating pre-existing in-
equalities that contribute to poorer health, lower incomes
and decreased physical and intellectual ability [109].
Inadequate nutritional intake is undeniably associated
with poor reproductive health in both men and women. In
men, it correlates with increased testicular and seminal
oxidative stress and associated sperm DNA fragmenta-
tionandimpairedchromatincondensation. Epigenetic
modulation has been reported, with transmission to the
offspring [110]. However, direct causality has not been
demonstrated.
Inadequate nutrition is closely linked to female
reproductive pathophysiology [111]. Deficient food intake,
insufficient nutritional diets, extreme dietary restrictions
and general lack of nutrients result in loss of both body
weight and physical performance, delayed puberty, post-
partum time lengthening to pregnancy, lower levels of
gonadotropin secretion with hormonal cyclicity changes
and increased infertility. Poor intakes of proteins, micro-
and macro-minerals and vitamins are associated with
reduced reproductive efficiency, as the altered energy
balance is directly correlated with reduced ovulatory
maturation in women. It was reported that maternal
malnutrition adversely affects foetal health, resulting in
Jegasothy et al.: Climate change and fertility in Malaysia 9
poor development and altered body composition with low
muscle mass, poor brain development and metabolism
[112, 113], modulations at the hormonal crosstalk, receptor
expressions as well as genetic and epigenetic constitutions
[113, 114]. In the long term, these alterations will result in
low cognitive development, incompetency in education,
low immunity, inadequate working potential and an
increased risk of several chronic diseases [112]. It was also
proposed that there exist “proximal levers”to facilitate
positive attitudes and measures to ensure optimal foetal,
infant and childhood nutrition [115].
Future perspectives and conclusion
The projections of climate change in Malaysia over the next
few decades are worrying enough with speculation of
extreme variations in rainfall, increase in ambient tem-
perature and lack of clean water (Table 2: [116–120]). These,
even at less than extreme levels may affect the fertility
parameters of Malaysian population which is already
following a declining trend and the climate change may be
an essential role player in the process, either directly or
indirectly. The direct impact of climate change on repro-
ductive functions may involve heat-induced physiological
alterations that impair the structure and functions at the
tissue or cellular levels or disrupt the orchestration of
hormones regulating the reproductive functions. There are
number of indirect means by which climate change can
affect fertility. Flood, drought or even fluctuations in
ambient temperature may facilitate emergence of novel
infectious micro-organisms that can cause and spread both
systemic and reproductive infections leading to subfertility
or infertility. In addition, climate changes, national socio-
economic status and food supply are closely linked, and
sociodemographic or economic alterations are in turn
important determinants of fertility rate in a population.
Moreover, deterioration in quality or quantity of food in
any region, may severely affect overall health as well as
fecundity of the population. Since, Malaysia lacks proper
research to support the possible effects of climate change
on fertility, the present report provides a probable scenario
based on worldwide evidence of the mechanism by which
Malaysian fertility is and will fall victim of the ongoing
climate changes, and thereby, further studies should be
encouraged in this direction.
Research funding: None declared.
Author contributions: R Jegasothy: Conceptualization,
Manuscript editing and review. P Sengupta: Literature
search, Manuscript writing, Manuscript editing and review.
S Dutta: Literature search, Manuscript writing, Manuscript
editing and review. R Jeganathan: Manuscript editing and
review. All authors have accepted responsibility for the
entire content of this manuscript and approved its
submission.
Competing interests: Authors state no conflict of interest.
Table :Predictions of future climate change.
Source Prediction
Malaysian Meteorological
Department ()[]
The estimated rise in temperature till is between .and .°C for East Malaysia and between .°C and
.°C for the Peninsular Malaysia. Owing to its highly variable precipitation-modulating factor, no certain
precipitation pattern was reported. During the st century, the precipitation on the West Coast increased and
precipitation on the East Coast of the Peninsular Malaysia decreased. Until the end of st century, major rises
in precipitation were expected over west Sarawak.
Kwan et al. [] Between and , increased probability of intense rains on the west coast of Malaysia was expected in
September to November. In some areas of Malaysian Borneo, early monsoon rainfall was predicted. Higher
frequency of extreme warm temperatures and small decreases in cold extremes were forecast.
Loh et al. [] The rise in temperature between .and .°C, .–.°C and .–.°C was projected at the national level by
the end of the st century in three different emission scenarios (A,AB and B). For drier months from
December to May, and rain months from June to November, a high rainfall variability was expected.
Syafrina et al. [] RCP .scenarios were used to predict increase in rainfall in hours and h from the year –, with a
wider spatial distribution.
Amin et al. [] In November from to , and also in November and December from to , the simulation
showed a substantial increase in mean monthly flows in the Dungun watershed. The rise in flow from April to
May and July to October has been projected between and for Muda Watershed. (GCM for climate
projection and watershed hydrology model (WEHY) for hydrologic simulations over Muda and Dungun
watershed in the Peninsular Malaysia)
10 Jegasothy et al.: Climate change and fertility in Malaysia
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