Causes of Low Sperm Count and Motility

Sperm and Ovum
The male gametes (sperm) are approaching a female gamete (an unfertilized egg) prior to conception.

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One of the primary causes of infertility is low sperm count and motility. That, coupled with poor sperm quality, represents 90% of all cases of infertility in men and anywhere from 20% to 40% in couples.

It is a frustrating and often disheartening condition that affects nearly one in six men. Causes range from hereditary factors and lifestyle choices to past infection and age.

Characteristics of Low Sperm Count and Motility

Oligoasthenoteratozoospermia (OAT) is the term we used to describe this condition. By definition, OAT is characterized by semen with the following qualities:

  • An abnormally low amount of sperm (oligozoospermia)
  • An abnormally low amount of sperm with good motility (asthenozoospermia)
  • An abnormally low level of sperm of a healthy shape (teratozoospermia)

The term oligoasthenoteratozoospermia is used when all three factors are present.

Idiopathic oligoasthenoteratozoospermia is used when the cause of the condition is unclear. Up to 30% of male infertility cases are said to have idiopathic OAT.

Causes and Treatment of OAT

The factors for OAT can be broadly broken down into four categories: genetic factors, lifestyle factors, and testicular factors, and testicular/ejaculatory dysfunction.

Genetic factors can affect every stage of male fertility, ranging from DNA damage in sperm cells (spermatozoa), genetic defects of the Y chromosome, and genetic disorders like Klinefelter syndrome. Most of the factors are not treatable per se but can often be overcome with the use of in vitro fertilization (IVF).

Lifestyle factors involve both habits and conditions that directly affect the man's sperm. Many of these factors are changeable and can significantly improve a man's chance of conceiving. Among them:

  • Smoking is strongly linked to male infertility although the reasons are not entirely clear. What we do know is that smoking can reduce the sperm count by 17.5% and sperm motility be 16.6%.
  • Alcohol consumption of a little as five drinks per week can significantly lower a man's testosterone and the quality of his sperm. Many recreational drugs have the same effect.
  • Obesity (BMI over 30) is known to cause hormonal changes that can directly impact a man's fertility. Being seriously underweight (BMI under 18.5) is also a concern.
  • Strenuous riding (cycling, horseback) can cause testicular inflammation which can be relieved by simply taking a break from the activity.
  • Overheating the testes is associated with low sperm count. Causes include too hot showers baths, or sauna, as well as wearing tight briefs instead of boxers. Overexertion at the gym can also have the same effect.
  • Certain medications can also affect the quality of sperm (anabolic steroids, Tagamet used to treat stomach acid) while other cans affect sperm motility (Azulfidine used to treat rheumatoid arthritis and Macrobid used to treat bladder infections).

Testicular factors are those which interfere with the testicle's ability to produce ample quantity or quality of sperm. Some of the factors can be treated; others can't. They include:

  • Older age
  • Testicular trauma
  • Certain past infections (syphilis, mumps, malaria) that are known to either directly or indirectly affect the male reproductive system)
  • Enlargement of the varicocele (which can be often be treated surgically and non-surgically)
  • Testicular cancer
  • Chemotherapy and radiation therapy

Testicular and ejaculatory dysfunction refers to any condition that impedes a man's ability to ejaculate or obstructs the flow of semen in the male genital tract. These factors include:

  • Obstruction of the vas deferens or ejaculatory duct
  • Prostatitis (inflammation of the prostate gland)
  • Retrograde ejaculation where semen is inadvertently redirected to the bladder
  • Hypospadias, a congenital defect in which the opening of the urethra is not situated on the head of the penis
  • Erectile dysfunction (which can often be treated with medication)
  • Impotence by other causes

A Word From Verywell

While distressing, many of the causes of male infertility can be treated. In the event they can't, there are an array of assisted reproductive procedures that can improve a couple's chance of conceiving. They include fertility drugs, medical devices, surgery, or a combination of treatments. 

Whatever you do, don't give up. If faced with male infertility, whatever the cause, speak with a fertility specialist who may be able to help.

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  1. Kumar N, Singh AK. Trends of male factor infertility, an important cause of infertility: A review of literature. J Hum Reprod Sci. 2015;8(4):191-196. doi:10.4103/0974-1208.170370

  2. Cavallini G. Male Idiopathic Oligoasthenoteratozoospermia. Asian J Androl. 2016;8(2):143-157. doi:10.1111/j.1745-7262.2006.00123.x

  3. Punab M, Poolamets O, Paju P, et al. Causes of male infertility: a 9-year prospective monocentre study on 1737 patients with reduced total sperm counts. Hum Reprod. 2017;32(1):18-31. doi:10.1093/humrep/dew284

  4. Kovac JR, Khanna A, Lipshultz LI. The Effects of Cigarette Smoking on Male Fertility. Postgrad Med. 2015;127(3):338-341. doi:10.1080/00325481.2015.1015928

  5. Palmer NO, Bakos HW, Fullston T, Lane M. Impact of obesity on male fertility, sperm function and molecular composition. Spermatogenesis. 2012;2(4):253-263. doi:10.4161/spmg.21362