Summary of “Lifestyle causes of male infertility” 
Over the past few decades, there has arguably been a global decline in both sperm quality and quantity, although the true extent of changes remains an issue of ongoing debate among experts. The purpose of this article was to review available evidence regarding effects of men’s lifestyle factors on their reproductive health. The author, Damayanthi Durairajanayagam, reviewed literature on major lifestyle factors connected to male infertility from PubMed over a ten-year period (December 2008 to November 2017). We summarized a few of the lifestyle factors examined in the article: smoking, alcohol, recreational drugs, obesity, psychological stress, advanced paternal age, diet, and genital heat stress.
It is well known that cigarette smoke contains many carcinogens and harmful substances. Smoking is linked to leucocytospermia, or sperm with a high white blood cell count; leucocytospermia is an internal source of reactive oxygen species (ROS) leading to oxidative stress on the spermatozoa, which in turn affects sperm function and male fertility. Not only has smoking been linked to leucocytospermia, but it has also been linked to a decline in sperm quality and sperm concentration. It is negatively associated with sperm motility, count, and morphology. Tobacco smoking also leads to increases in aneuploidies (abnormal number of chromosomes in a cell), DNA damage, and mutations in sperm. As a combined result of cell apoptosis (cell death), higher oxidative stress levels, and DNA damage, cigarette smoking may have a negative effect on semen quality, and impair sperm maturation, function, and spermatogenesis (origin and development of sperm cells).
Alcohol is another lifestyle choice that contributes to male infertility. A recent meta-analysis reported that alcohol has a negative effect on sperm morphology and semen volume. Alcohol interferes with the male reproductive hormone production of LH, GnRH, FSH, and testosterone, and it impairs the functions of Sertoli and Leydig cells (male reproductive system); therefore, spermatozoa’s production, development and maturation could be affected. Also, spermatogenesis declines as alcohol use increases. Overall, chronic alcohol intake is connected to a harmful effect on the levels of male reproductive hormones and semen quality. Furthermore, a study done on the male partner of couples with infertility found teratozoospermia, or abnormal sperm morphology, was present in 63% of males who drank alcohol moderately (40-80 g/day) and in 72% of males who drank alcohol heavily (>80 g/day). Overall, male reproductive function was dependent on the amount of alcohol consumed. The author stated, “Moreover, it must be kept in mind that whilst alcohol intake and cigarette smoking alone did not affect sperm parameters, both habits together appear to exert an additive effect that could adversely alter sperm parameters.”
Recreational drugs like cocaine, opiates (narcotics), marijuana, anabolic-androgenic steroids (AAS), and methamphetamines are drugs that have a negative impact on male fertility and could impair HPG axis, sperm function, and testicular architecture. Marijuana use alone in young men, the most abused illicit drug, was found to lower sperm count and concentration (smoking more than 1x week within the last 3 months). Additionally, increased exogenous testosterone (from AAS), also led to fertility issues by creating negative feedback on the HPG axis causing testicular atrophy, infertility, and reversible suppression of spermatogenesis.
Obesity is another lifestyle factor that can contribute to infertility in men. Males with a body mass index (BMI) of 25-29 kg/㎡ are considered overweight, and males with a BMI of ≥30 kg/㎡ are considered obese. In a systemic review of 30 studies, the author found that obese men had a higher percentage of sperm with DNA fragmentation, low mitochondrial membrane potential (MMP), abnormal morphology, and higher likelihood of infertility. A meta-analysis found that obese men were more likely to be azoospermic (lacking mobile sperm) or oligozoospermic (low sperm count) compared to men in a normal weight range. The authors stated, “The presence of excess white adipose tissue in obese individuals causes increased conversion of testosterone to oestrogen, and affects the HPG axis leading to a reduction in gonadotrophin release. These effects result in secondary hypogonadism and impaired spermatogenesis.”
Psychological stress may also affect male fertility. Ultimately, the impairment of testosterone secretion is detrimental to spermatogenesis and is triggered when experiencing stress. With stress, the sympathetic nervous system and the hypothalamus-pituitary-adrenal (HPA) axis are triggered. The HPA and gonadotrophin-inhibitory hormone (GnIH) have a repressive effect on testicular Leydig cells and the HPG axis. This in turn reduces testosterone levels, which then creates changes in the blood-testis barrier and Sertoli cells, causing spermatogenesis suppression. Overall, psychological stress is associated with abnormal semen parameters and reduced paternity.
Several other factors contribute to male infertility including advanced paternal age, diet, and genital heat stress. In a retrospective study involving 5,081 men, a decline in sperm parameters with age was discovered. After 34 years of age total motile sperm and total sperm count declined. Thus, the likelihood of pregnancy goes down with men aged >34 years (separate from women’s age). They do not know what causes the age-associated decline, but normal aging physiological factors and environmental factors could play a role. In addition, diet plays a role in fertility in men. A systematic review of observational studies found that a healthy, balanced diet (e.g., Mediterranean diet) could improve fecundity rates and semen quality in men. Therefore, foods like fish, poultry, fruit, vegetables, cereals, and low-fat dairy are linked to sperm quality. Conversely, foods like full-fat dairy, processed meat, coffee, alcohol, and sugar-sweetened beverages are linked to poor semen quality and thus lower fertility rates. One final factor affecting male fertility is worth mentioning: genital heat stress due to scrotal hyperthermia. Varicoceles (varicose veins in scrotum), cryptorchidism (undescended testes), and exposure to radiant heat or prolonged hours of sitting can lead to testicular heat stress causing spermatogenic arrest, oxidative stress, sperm DNA damage, and germ cell death.
All in all, there are many lifestyle factors that can affect male fertility: smoking, alcohol, recreational drugs, obesity, psychological stress, advanced paternal age, diet, and genital heat stress, just to name a few. While some of these factors may be outside of one’s control, many of them are modifiable and can lead to improved fertility.
Reference
Durairajanayagam, D. (2018). Lifestyle causes of male infertility. Arab J Urol, 16(1): 10-20. DOI: 10.1016/j.aju.2017.12.004
