There have been reports of air pollution and its impacts on male fertility. Several studies have been conducted in the Czech Republic regarding men living in two different locations, one more polluted than the other [134,135]. Men who are exposed to higher levels of air pollution were more likely to experience abnormal sperm morphology, decreased motility, and an increased chance of DNA fragmentation (n = 48 or 408 respectively). There was also a significant negative correlation found between sperm concentration and the amount of ozone to which a man was exposed (n = 5134) [136].
Heavy metals include metals such as lead, mercury, boron, aluminum, cadmium, arsenic, antimony, cobalt, and lithium. Only a few such heavy metals have been researched in connection to reproductive function. Lead, which is commonly found in batteries, metal products, paints, ceramics, and pipes, is one of the most prominent heavy metals. Lead interrupts the hypothalamic-pituitary axis and has been reported to alter hormone levels [132,138], alter the onset of puberty, and decrease overall fertility [132]. Lead may alter sperm quality in men, and cause irregular menstruation, induce preterm delivery, and cause miscarriage, stillbirth, and spontaneous abortion in women [132]. Mercury is commonly found in thermometers, batteries, and industrial emissions. Mercury concentrations increase in the food chain, resulting in bioaccumulation that can negatively impact reproduction in humans who consume food, usually tainted seafood [132]. Ultimately, mercury can disrupt spermatogenesis and disrupt fetal development [138]. Boron is another heavy metal that is used in the manufacturing of glass, cement, soap, carpet, and leather; its effects on the hypothalamic-pituitary axis are comparable to lead [138]. While there is not much research on cadmium, it has been shown experimentally to cause testicular necrosis in mice, as well as marked changes in libido and infertility [139].
Many of the chemicals used world-wide in today’s society, including pesticides and endocrine disruptors, among others, may have various damaging effects on the reproductive health of both men and women. Mimicking natural hormones, impeding normal hormone activity, and varying regulation and function of the endocrine system are a few of the many ways that endocrine disruptors influence one’s body [138]. Numerous studies have reported negative effects of a variety of chemicals on reproductive health [132,138,140-144] (Table 2).
Both men and women can be exposed to chemicals and other materials that may be detrimental to their reproductive health while on the job. Heavy metals and pesticides, as outlined in Table 2, have many negative side effects, particularly for those who work around them. Men working in agricultural regions and greenhouses which use pesticides have higher concentrations of common pesticides in their urine [145], overall reduced semen parameters [146], oligozoospermia [15], lower sperm counts [147], and sperm concentrations decreased by as much as 60% [148]. Organic solvents may also prove detrimental. Men who work with these substances often experience indirect consequences with their female partner having decreased implantation rates (n = 726) [149]. Welding is another possible source of occupational exposure, and plays a role in reduced reproductive health [15,150]. There are also consequences for working in factories that manufacture chemicals and heavy metals. Factories that produce batteries where workers are exposed to lead may have negative impacts on reproductive capabilities, including asthenospermia and teratospermia (n = 150) [151]. Hobbies, while not often associated with excessive amounts of exposure, may be just as damaging as manufacturing. Gardeners may be in contact with pesticides [150]; crafters making jewelry, ceramics, and even stained glass may come in contact with lead [132]; painters may also come in contact with lead-based paints [150]. Whether it is manufacture or hobby, using any kind of heavy metal or pesticide likely will result in some exposure, and possibly reduce fertility.
Exposure to various kinds and amounts of radiation can have lasting effects in humans. Radiation that is in the form of x-rays and gamma rays can be devastating to the sensitive cells of the human body, including germ and Leydig cells. The damage done depends on the age of the patient and dose, and ultimately can result in permanent sterility [2,152].
The incredible convenience of the cell phone has dramatically increased its usage in the last decade. However, it does not come without negative effects. There have been an increasing number of studies demonstrating negative effects of the radiofrequency electromagnetic waves (RFEMW) utilized by cell phones on fertility. Cell phone usage has been linked with decreases in progressive motility of sperm [153], decreases in sperm viability [153,154], increases in ROS [154], increases in abnormal sperm morphology, and decreases in sperm counts [153]. One study evaluating 52 men demonstrated that men who carried a cell phone around the belt line or hip region were more likely to have decreased sperm motility (49.3 ± 8.2%) compared to men who carried their cell phones elsewhere or who did not carry one at all (55.4 ± 7.4%; P < .0001) [155]. Link between cell phones and fertilization capacity. Falzone et al. reported that when exposed to RFEMW, sperm head area significantly decreased from 18.8 ± 1.4 μm2 to 9.2 ± .7 μm2 and acrosomal area significantly decreases from 21.5 ± 4% to 35.5 ± 11.4% (P < .05) [156]. In addition, Falzone et al. found the mean number of sperm binding to the zona was significantly less in the exposed group (22.8 and 31.8 respectively) [156]. While amount of research demonstrating negative effects of cell phone usage and fertility grows, there can be no clear conclusion as no standard for analyzing cell phone effects is available and many studies have limitations [157,158]. Another aspect to consider is the effect of text-messaging on the body, as it is becoming more prevalent in respect to making phone calls. While technology quickly advances, research lags behind [159], providing the opportunity for unforeseen damage to occur.
While contraceptives are often associated with preventing pregnancy, several studies have demonstrated that both condom usage and oral contraceptives can preserve fertility in women [8,160]. In 2010, Revonta et al. concluded that infertile women used less oral contraception [117]; women who considered themselves infertile might be less inclined to use contraceptives [8]. Contraceptives are believed to reduce the chances of contracting a sexually transmitted infection, thus reducing infertility. Contraceptives also may decrease time to conception. In one study, condom users had shorter time to conception compared to oral contraceptive users; oral contraceptive users in turn had shorter time to conception than those women not using any contraceptives [117]. In addition, oral contraceptives were demonstrated to have positive effects on the prevention and management of endometriosis and pelvic inflammatory disease [117]. This evidence suggests that contraceptives may increase a woman’s fertility, lending to the overall fertility of the couple.
Scheduling regular doctor appointments may be beneficial for fertility. Males tend to not seek medical treatment for sexual dysfunctions or infections. It was reported that when men experience sexual problems, only 10.5% seek help (n = 11,161) [157]. When the problems become on-going, 20.5% of men turn to health care professionals [161]. Mercer et al. concluded that the low amount of males seeking treatment is most likely due to lack of awareness of treatment and guidance [161].
For women, visiting the gynecologist to receive an annual pap smear has been associated with being protective of fertility (n = 10,847) [160]. Kelly-Weeder and Cox also concluded from their study that when a woman reports her health status as good, she is more likely to be fertile. Both pap smears and self-reported health status may be related to better screening for disease, STI detection, more available information, and overall better access to care.
The type of clothing a man chooses to wear, may have effects on reproductive health. Many studies have been conducted hoping to find an answer to the question of what type of clothing is best for fertility. The view that elevation of scrotal temperature negatively impacts spermatogenesis and sperm parameters is universally acknowledged [162]. But the question of whether tight-fitting underwear actually has an effect on scrotal temperature and therefore semen quality has long been debated. There have been studies that have found significantly higher temperatures with tight-fitting clothing versus loose-fitting or no clothing [163,164]. Increases in scrotal temperatures could be due to an increase in temperature of about 3.5°C of the air between the clothing and the skin in comparison the ambient air [164].
One study followed 20 participants who wore tight-fitting underwear for 6 months then switched to loose-fitting underwear for 6 months [165]. Semen samples were taken every 2 weeks for the duration of the study. While half of the participants dropped out, there was a significant 50% decrease in sperm parameters in the tight-fitting versus loose-fitting underwear, demonstrating that the effects of tight-fitting underwear reversible. In another study, men who wore tight-fitting underwear and pants had a relative risk of 2.5 of having impaired semen quality [166]. They also noted that only wearing one or the other caused an insignificant decrease in semen quality. While there are studies that conclude that the type of underwear influences scrotal temperature, there are also some that did not find significant temperature differences [167,168].
Literature providing evidence that wet heat is tied to infertility is scarce. Many fertility authorities rely on the data provided from research of the effects of temperature on sperm function and then apply the idea to hot baths, jacuzzis, or saunas. One study conducted by Shefi et al. actually studied the effects of wet heat on 11 male subjects who were exposed to wet heat for greater than 30 minutes every week for at least 3 months prior to any experimentation [169]. These 11 men were then told to avoid wet heat exposure for 3 months. Three different semen samples were assessed: one from the onset of the study representing the exposed, one before 3 months into the experiment, and another at 3 to 6 months. Nearly half of the participants saw an increase in semen quality. Sperm motility saw a significant 22% increase for responders, and the improvement appeared to continue longer than 3 months (P = .02). When reviewing the non-responders, Shefi et al. found that other lifestyle factors could have accounted for the lack of semen quality increase, such as tobacco use.
Many sexually active couples choose to utilize vaginal lubricants to treat vaginal dryness and pain during intercourse [170]. While attempting to conceive, nearly 75% of participating couples reported to an internet study that they used lubricants to ease the female partner’s vaginal dryness, and 26% had claimed that they almost always used a lubricant [171]. Some non-commercial products used as lubricants include olive oil, vegetable oil, and saliva, and they have been demonstrated to negatively impact sperm function. Several products available to the public have been researched for possible effects on sperm function. A study conducted by Agarwal et al. compared Replens, Astroglide, FemGlide, K-Y Jelly, and Pre ~ Seed against a control medium [170]. In relation to the control, Astroglide, FemGlide, and Replens all significantly decreased sperm motility after 30 minutes of contact with semen (P < .01). Astroglide and Replens had a greater impact on motility in comparison to FemGlide’s. They also found that FemGlide and K-Y Jelly significantly increased sperm chromatin damage in comparison to the control medium (P < .05). While Pre ~ Seed caused an increase in chromatin damage, it was not significant.
Lifestyle factors, including age when starting a family, nutrition, weight management, exercise, psychological stress, cigarette smoking, recreational and prescription drugs use, alcohol and caffeine consumption, environmental and occupational exposures, preventative care, and other behaviors are modifiable and may impact fertility.
The evidence suggests that age may play a large role in determining fertility. Attempting pregnancy before the age of 30 for women and before 35 for men may provide the highest chances of success. While it is important for one partner to consider their age, it is when both partners consider their ages together that they may be able to thoroughly increase their odds of having a successful pregnancy.
Proper nutrition, weight, and exercise may impact fertility. Though no definitive link has been drawn, choosing proper nutrition, whether it be choosing supplements or food groups, before and during attempts to conceive may be vital for improving fertility for both men and women. Men and women who are underweight or overweight are also at risk for negative side effects, including changes in hormone levels that heavily influence their fertility. Recent research suggests that weight plays an important role in fertility, and controlling and maintaining an ideal weight may provide a way for couples to increase their fertility. Exercise is suggested to be beneficial, though too much may be detrimental. Lean and underweight men or women who exercise vigorously may put themselves at risk for a decrease in fertility, thus finding a balance may provide the best chances of achieving a pregnancy.
While there are associations between psychological effects and infertility, it is hard to establish a cause-effect relationship. Tests are subjective, and there is no general consensus on how to measure psychological stress [2]. It is also worth noting that it is difficult to isolate psychological effects because subjects who are more depressed and anxious are also more inclined to participate in lifestyles that may negatively influence fertility, such as consuming alcohol [65]. Couples attempting to conceive may try relaxing and reducing exposure to stressors in an effort to increase fertility [76].
Recreational and prescription substances also appear to have significant impact on fertility. Though clear links are yet to be determined, there are negative trends, including decreased semen parameters or decreased ovarian reserve, associated with smoking and fertility. If couples are attempting to achieve a pregnancy, limiting or smoking cessation may provide more positive outcomes. It is difficult to establish a link between illegal drug use and infertility as there are many ethical issues that prevent researchers from discovering a definitive relationship. Researchers have also had issues with drawing a definitive link between infertility and prescription medication, which often have known side effects, though fertility side effects are not often a concern when prescribing. Further research on many medications and drugs is needed in order to make any recommendations. While there is evidence to support that alcohol does have an impact on fertility, it is also difficult to establish a definitive link as there is no standard “drink” or comparative way to measure alcohol consumption. Despite these drawbacks to recent research, decreasing or ceasing alcohol consumption may provide a better chance of achieving a viable pregnancy for the couple. Though caffeine appears to have a negative effect on fertility, additional research is needed to elucidate if there is a definitive relationship.
Concerning environmental exposures, assessing the exposures of each individual may be crucial to reproductive health of the couple. Eliminating every exposure is unrealistic; however, identifying, eliminating, or minimizing even one factor may have significant positive effects on fertility for both men and women.
Dr Eliran MorTaking care of a current fertility problem may provide better fertility in the future. Taking preventative steps such as visiting your doctor and using contraception may help fertility. Making appointments with a doctor for both preventative measures and when problems arise may assist in increasing fertility for both men and women. In addition, using appropriate contraception may have a positive impact on a couple’s fertility. Other factors such as clothing choice, wet heat, and lubricants may also impact a couple’s fertility. Overall, while there is suggestive data, a clear negative influence of the type of underwear or clothing on semen quality has not been proven, and the overall effects on a couple’s fertility are still unknown. While there is suggestive data, there is very little actual evidence linking wet heat and fertility to suggest cessation of the use of wet heat. Research suggests that some lubricants can be beneficial for couples trying to conceive, and some lubricants may be detrimental to fertilization. Choosing an appropriate lubricant may provide the couple with improved chances of achieving a pregnancy.
The lifestyle factors discussed in the present review have the potential to impact fertility. It is important to understand the ways in which lifestyle behaviors may benefit or harm fertility in order to minimize complications and to maximize fertility outcomes. By understanding the impact of lifestyle on reproductive health, and by actively modifying lifestyle behaviors, men and women are capable of controlling their own fertility potential.
OR: Odds ratio; ROS: Reactive oxygen species; IUI: Intra uterine insemination; MDA: Malondialdehyde; RR: Relative risk; BMI: Body mass index; ED: Erectile dysfunction; SHBG: Sex Hormone-Binding Globulin; GnRH: Gonadotropin-Releasing Hormone; LH: Luteinizing Hormone; HA: Hyaluronan; TAC: Total antioxidant capacity; FSH: Follicle stimulating hormone; RFEMW: RadioFrequency ElectroMagnetic Waves; BPA: Bisphenol A; DDT: DichloroDiphenylTrichloroethane; DDE: DichloroDiphenyldichloroEthylene; 5-ASA: 5-Aminosalicylic acid.
RKS conceived the study, participated in the study design compilation of the contents and critical review of the paper. KRB and JMF were responsible for literature (Medline) search, compilation of the information, drafting and finalizing the paper. AA provided substantial contribution ranging from study idea, design, and critical review of the final paper. All authors read and approved the final manuscript.
KRB and JMF were summer interns at the Center for Reproductive Medicine, Glickman Urological & Kidney Institute, Cleveland Clinic, Cleveland, Ohio. RS is the Coordinator of the Center for Reproductive Medicine, Cleveland Clinic, Cleveland Ohio. AA is the Director of the Center for Reproductive Medicine, Cleveland Clinic, Cleveland Ohio.
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