A risk factor is something that increases your likelihood of getting a disease or condition.
It is possible to develop infertility with or without the risk factors listed below. However, the more risk factors you have, the greater your likelihood of developing infertility. If you have a number of risk factors, ask your doctor what you can do to reduce your risk.
Risk factors for infertility in men include:
The toxins in cigarette smoke negatively affect sperm quality. The concentration of sperm in semen is decreased, sperm motility (movement) is reduced, and the number of abnormal sperm is increased. Smoking also has adverse effects on hormone levels and may affect the cells in the testes that produce testosterone.
Use of Alcohol, Drugs, and Anabolic Steroids
Although moderate alcohol consumption does not affect male fertility, excessive alcohol intake alters hormone levels and reduces sperm count and sperm quality. Like cigarette smoking, use of marijuana also can adversely affect sperm count, sperm motility, and sperm morphology. It also reduces plasma testosterone levels. Use of cocaine negatively affects sperm parameters as well as the ability of sperm to penetrate cervical mucus. Opioids may reduce fertility in men by altering hormone production. Anabolic steroids are sometimes used to increase muscle mass or strength, but they also influence production of reproductive hormones and can reduce fertility.
Sexually Transmitted Diseases
Unprotected sexual intercourse (intercourse without a condom) increases your risk of developing a sexually transmitted disease (STD). Several STDs, including gonorrhea and chlamydia, often produce no symptoms, especially in men, so you may not know you are infected. Untreated STDs can cause scarring in the sperm-carrying tubes, which reduces the number of sperm in ejaculate and increases the risk of fertility problems. Use of lubricants during intercourse, however, may contribute to fertility problems since many of these products contain spermicides that are toxic to sperm.
The testicles are easily damaged during vigorous sporting events or fights. These injuries can cause inflammation that reduces the blood supply to the testicles, which can permanently damage sperm-producing cells.
Moderate exercise increases sperm production and may have beneficial effects on fertility. However, excessive exercise, such as that performed by long-distance runners, reduces sperm production.
Exposure to Toxic Chemicals or Heavy Metals
Numerous chemicals used in industry or found in the environment as contaminants have been linked to male infertility. These include organochlorine pesticides, lead, cadmium, aniline, dyes, dioxins (used to bleach paper products), and vinclozolin (a fungicide used on food). These chemicals are thought to reduce fertility by disrupting hormone function.
Exposure to Excessive Heat
Some evidence suggests that heat exposure, such as occurs when using a sauna or hot tub, may affect sperm quantity and quality.
Tight Shorts and Pants and Hard Bicycle Seats
Underwear and clothing that is tight and constricting may reduce blood flow in the groin and adversely affect sperm production. Other evidence indicates that certain bicycle seats may cause circulatory and neurologic damage in the groin that can affect erectile function.
Malnutrition or Obesity
Men with very poor nutritional status may have reduced fertility. Being obese or underweight may reduce fertility.
Excessive and/or prolonged emotional stress may also reduce fertility.
The following medications can cause subfertility or even infertility. Examples include cimetidine, colchicine, allopurinol, and minoxidil.
Medical Conditions and Treatments
High fevers due to flu or pneumonia can adversely affect sperm parameters, although these effects are generally short-term. Other infections, including viral infections such as mumps and prostatitis, can cause inflammation of the testicles and thereby reduce fertility. Tuberculosis can produce blockages in the sperm-carrying tubes. Antibiotics that can lead to subfertility or infertility include: erythromycin, tetracycline, sufasalazine, nitrofurantoin, and ketoconazole.
The long-term complications of diabetes can produce blood vessel and nerve abnormalities that lead to problems with erection and ejaculation.
High blood pressure itself, as well as many of the medications (alpha blocker, calcium channel blocker, spirorolactone) used to treat it, can cause erectile problems.
The build-up of plaque in the arteries, including those of the penis, can create erectile problems. These may be exacerbated by medications used to treat cardiovascular disease.
Chronic kidney failure can reduce sperm quality and can also lead to erectile difficulties.
Some cancers affect the brain or other hormone-producing tissues and can affect fertility directly. In other instances, the radiation or chemotherapy used to treat cancers at other sites may severely reduce or stop sperm production.
Genetic and Congenital Factors
Cystic fibrosis is an inherited disorder characterized by excessive production of mucus. Men with cystic fibrosis are infertile due to the absence of sperm, vas deferens, or seminal vesicles.
Sickle cell anemia is an inherited disorder in which the structure of hemoglobin, the oxygen-carrying protein in blood, is abnormal. It can contribute to infertility because the testes may be underdeveloped.
Chromosome disorders, including conditions such as Klinefelters syndrome, occur in 2% to 20% of infertile men. These can influence fertility by disrupting cell division or by altering the development of the testicles.
Some men are born with abnormalities of the reproductive organs, such as the absence of the sperm-carrying tube, which prevent sperm from being released into semen. Undescended testicles can also be a cause of infertility.
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Last reviewed November 2018 by EBSCO Medical Review Board Adrienne Carmack, MD Last Updated: 1/29/2018