Semen quality and association with coffee drinking, cigarette smoking, and ethanol consumption

Investigating the association between alcohol intake and male reproductive function: A current meta-analysis

Background

Alcohol use and alcohol-related health problems are on the rise in developing countries. This meta-analysis was conducted to determine the effects of alcohol consumption on human male reproductive function through semen parameters, antioxidants in semen, sperm DNA fragmentation, and sex hormones.

Methods

Studies regarding the effects of alcohol consumption on male reproductive function were searched on databases. Based on the random-effects model, STATA software was used to analyze and synthesize the selected studies. Alcoholics, moderate alcoholics, heavy alcoholics, and no alcoholics values were compared using the standard mean difference. Publications were assessed for publication bias by the Egger test.

Result

Forty studies were selected from databases examining the effect of alcohol consumption on male reproductive health in 23,258 people on five continents of the world. The meta-analysis revealed that alcohol intake reduced semen volume during each ejaculation (SMD = -0.51; 95% CI -0.77, -0.25). However, there were no significant associations with other semen indicators such as density, mobility, and normal and abnormal sperm count from this analysis. In addition, drinking alcohol lowered antioxidant enzymes in semen (SMD = -7.93; 95% CI -12.59, -3.28) but had no effect on sperm DNA fragmentation. Finally, the results showed a decrease in general testosterone levels (SMD = -1.60; 95% CI -2.05, -1.15), Follicle Stimulating Hormone (SMD = -0.47; 95% CI -0.88, -0.05), Luteinizing Hormone (SMD = -1.35; 95% CI -1.86, -0.83), but no effect in other sex hormones named as estradiol, Inhibin B and Sex Hormone-Binding Globulin. Furthermore, when analyzing subgroups at different drinking levels, the results showed that the moderate alcoholic group (less than 7 units/week) had no change in the semen index. Meanwhile, the group of heavy alcoholics (more than 7 units/week) harmed the semen index and sex hormones, especially by increasing estradiol.

Conclusion

There is evidence that alcohol consumption affected semen volume and antioxidant, reproductive hormones thus negatively affecting male reproductive function. This study might be necessary to make recommendations regarding alcohol consumption for men.

Addiction and human male fertility: A systematic review and a critical appraisal

BACKGROUND

Addiction is a global problem that has many negative consequences on human health as well as the quality of life.

OBJECTIVES

This review aimed to assess the effect of addiction on human male fertility.

METHODS

A systematic review was conducted on various electronic sites.

RESULTS

The initial literature search identified a total of 5239 articles in all searched databases. After removing duplicates and application of inclusion/exclusion criteria,177 were potential articles, 112 were omitted because no direct relevance was encountered. Finally, 65 studies were retained for review. They were classified according to the type of addiction into; opioids and cannabinoids (18 articles), alcohol (7 articles), cocaine (2 articles), Androgenic Anabolic steroids AAS (15 articles), tobacco (10 articles) and caffeine (13 articles). Most of these recruited articles demonstrated a negative impact of the addressed substance on male fertility with variable levels of evidence.

CONCLUSIONS

It was concluded that addiction harms human male fertility that should be put into consideration. More future studies are needed after a proper methodological and statistical approach, including logistic regression analysis, to predict the effect of a specific substance on human male fertility. This article is protected by copyright. All rights reserved.

Do lifestyle practices impede male fertility?

Alongside an increasing prevalence of couple and male infertility, evidence suggests there is a global declining trend in male fertility parameters over the past few decades. This may, at least in part, be explained through detrimental lifestyle practices and exposures. These include alcohol and tobacco consumption, use of recreational drugs (e.g., cannabis, opioids and anabolic steroids), poor nutritional habits, obesity and metabolic syndrome, genital heat stress (e.g., radiation exposure through cell phones and laptops, prolonged periods of sitting, tight-fitting underwear and recurrent hot baths or saunas), exposure to endocrine-disrupting chemicals (e.g., pesticide residue, bisphenol A, phthalates and dioxins) and psychological stress. This review discusses these lifestyle practices and the current evidence associated with male infertility. Furthermore, known mechanisms of action are also discussed for each of these. Common mechanisms associated with a reduction in spermatogenesis and/or steroidogenesis due to unfavourable lifestyle practices include inflammation and oxidative stress locally or systemically. It is recommended that relevant lifestyle practices are investigated in clinical history of male infertility cases, particularly in unexplained or idiopathic male infertility. Appropriate modification of detrimental lifestyle practices is further suggested and recommended in the management of male infertility.

Tracking research trends and hotspots in sperm DNA fragmentation testing for the evaluation of male infertility: a scientometric analysis

BACKGROUND

This article describes the research trends in sperm DNA fragmentation (SDF) over the past 20 years (1999-2018) using a scientometric approach.

METHODS

A stepwise approach was adopted to retrieve scientometric data (articles per year, authors, affiliations, journals, countries) from Scopus and analyze the publication pattern of SDF with reference to key areas of research in the field of Andrology.

RESULTS

A total of 2121 articles were retrieved related to SDF. Our data revealed an increasing research trend in SDF (n = 33 to n = 173) over the past 20 years (R² = 0.894). Most productive country in publications was the USA (n = 450), while Agarwal A. (n = 129) being the most productive author. Most of the articles in SDF were primarily focused on lifestyle (n = 157), asthenozoospermia (n = 135) and varicocele (130). Mechanistic studies on SDF were published twice as much as prognostic/diagnostic studies, with significant emphasis on oxidative stress. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was the most widely used technique to evaluate SDF. Publications on SDF related to assisted reproductive techniques also showed a linear increasing trend (R² = 0.933).

CONCLUSIONS

Our analysis revealed an increasing trend in SDF publications predominantly investigating lifestyle, asthenozoospermia and varicocele conditions with TUNEL being the most widely used technique. A substantial increase in research is warranted to establish SDF as prognostic/diagnostic parameter to evaluate clinical scenarios and ART outcomes.

Coffee and caffeine intake and male infertility: a systematic review

BACKGROUND

Semen quality, a predictor of male fertility, has been suggested declining worldwide. Among other life style factors, male coffee/caffeine consumption was hypothesized to influence semen parameters, but also sperm DNA integrity. To summarize available evidence, we performed a systematic review of observational studies on the relation between coffee/caffeine intake and parameters of male fertility including sperm ploidy, sperm DNA integrity, semen quality and time to pregnancy.

METHODS

A systematic literature search was performed up to November 2016 (MEDLINE and EMBASE). We included all observational papers that reported the relation between male coffee/caffeine intake and reproductive outcomes: 1. semen parameters, 2. sperm DNA characteristics, 3. fecundability. All pertinent reports were retrieved and the relative reference lists were systematically searched in order to identify any potential additional studies that could be included.

RESULTS

We retrieved 28 papers reporting observational information on coffee/caffeine intake and reproductive outcomes. Overall, they included 19,967 men. 1. Semen parameters did not seem affected by caffeine intake, at least caffeine from coffee, tea and cocoa drinks, in most studies. Conversely, other contributions suggested a negative effect of cola-containing beverages and caffeine-containing soft drinks on semen volume, count and concentration. 2. As regards sperm DNA defects, caffeine intake seemed associated with aneuploidy and DNA breaks, but not with other markers of DNA damage. 3. Finally, male coffee drinking was associated to prolonged time to pregnancy in some, but not all, studies.

CONCLUSIONS

The literature suggests that caffeine intake, possibly through sperm DNA damage, may negatively affect male reproductive function. Evidence from epidemiological studies on semen parameters and fertility is however inconsistent and inconclusive. Well-designed studies with predefined criteria for semen analysis, subject selection, and life style habits definition, are essential to reach a consistent evidence on the effect of caffeine on semen parameters and male fertility.

Phosphodiesterase Inhibitors (PDE Inhibitors) and Male Reproduction

The nonspecific PDE inhibitors, particularly the methylxanthines: caffeine, pentoxifylline (PTX), and theophylline, are known to stimulate sperm motility in vitro and have been used to treat sperm prior to insemination. The in vivo effects are less dramatic. A beneficial effect of caffeine, which is a constituent of some medications, remains controversial. Very high doses of caffeine do have negative effects on fertility endpoints in men and experimental species. The specific PDE5 inhibitors, particularly sildenafil and tadalafil, are prescribed for erectile dysfunction, as well as pulmonary hypertension, lower urinary tract symptoms, and premature ejaculation. PDE5 is expressed throughout the contractile tissues of the male reproductive tract, generally increasing contractility. Some PDE5 inhibitors tend to increase circulating testosterone levels somewhat. For short-term exposure consistent with use prior to intercourse, there appears to be minimal effects on semen quality. Several large, randomized controlled trials (RCTs) in healthy men have not found adverse effects of long-term use of these drugs on semen quality. RCTs in infertile men have demonstrated a modest increase in semen quality. Animal studies at human equivalent doses (HED) have produced similar results in young males, but a study in aging male rats found progressive decreases in epididymal sperm quality accompanied by consistent degeneration of the seminal tubules suggesting that studies in older men might be warranted. A concerning study in mice found lower fertilization rates in males treated with HED of sildenafil and mated the next day to untreated females than for control males. Fertility studies in humans are needed.

Implication of caffeine consumption and recovery on the reproductive functions of adult male Wistar rats

BACKGROUND

This study assessed the impact of caffeine consumption and recovery on reproductive functions and fertility of Wistar rats.

METHODS

Thirty-five adult male Wistar rats were divided into seven groups of five rats each. Group A (control) received distilled water (vehicle), while groups B, C, and D were treated orally with 10 mg/kg body weight (BW), 20 mg/kg BW, and 40 mg/kg BW caffeine, respectively, for 30 days. Groups E, F, and G were treated orally with 10 mg/kg BW, 20 mg/kg BW, and 40 mg/kg BW caffeine, respectively, for 30 days and then allowed to recover for another 30 days.

RESULTS

Caffeine caused a decrease in body weight, while recovery groups showed appreciable increase in body weight during recovery. Relative weight of seminal vesicle, prostate, and epididymis decreased dose dependently during treatment but increased during recovery. The liver and kidney weight increased during treatment but reduced during recovery. Sperm count was significantly decreased in both treated and recovery groups. Initial decrease in sperm viability and volume was appreciably reversed during recovery period. Serum level of testosterone increased at high doses, while serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) showed significant decrease. Histological sections of testis in treated groups showed mild congestion of the interstitial blood vessel and subcapsular congestion. However, there was no subcapsular congestion in the recovery groups. All rats in both treated and recovery groups had 100% fertilization success from fertility study.

CONCLUSIONS

Suggestively, caffeine treatment for 4 weeks could impair body, reproductive organs weight, sperm characteristics, LH/FSH level, and also testicular cyto-architecture. Effects appeared, however, reversible after caffeine withdrawal.

In vitro fertilization embryo development from caffeine-treated murine sperm

Purpose

To evaluate the effect of long-term caffeine administration on murine sperm and subsequent in vitro fertilization (IVF).

Methods

Male mice were injected with various doses (0, 0.2 and 1.0 mg/mouse/day) of caffeine for 1 month. After sperm collection, the IVF rate and embryo development to the blastocyst stage were evaluated.

Results

The mean body weight significantly decreased in the 1.0 mg/day treatment group compared to the control group (P < 0.01). Testicular weight and histological features did not differ, and total blood testosterone was no different in spite of the difference between 0.2 and 1.0 mg/day of caffeine. The IVF rate differed significantly between the control group [100/105 (95.2 %)] and 0.2 mg/day group [106/121 (87.6 %)] (P < 0.05). Furthermore, blastocyst formation was significantly and dose-dependently lower with higher caffeine levels: control group: 85/100 (85.0 %); 0.2 mg/day group: 84/106 (79.2 %) (P < 0.05); 1.0 mg/day group: 64/102 (62.7 %) (P < 0.001).

Conclusions

Caffeine treatment affected body weight of male mice. However, testicular weight, histological features and total blood testosterone concentration were not statistically different. In addition, following IVF using sperm from these mice, blastocyst formation decreased in a dose-dependent manner. These findings suggest that embryo development from oocytes fertilized with sperm from caffeine-administered male mice is negatively affected.

Habitual alcohol consumption associated with reduced semen quality and changes in reproductive hormones; a cross-sectional study among 1221 young Danish men

OBJECTIVE

Study associations between three measures of alcohol consumption (recent, typical/habitual, binging), semen quality and serum reproductive hormones.

DESIGN

Cross-sectional population based study.

SETTING AND PARTICIPANTS

1221 young Danish men, aged 18-28 years were recruited when they attended a compulsory medical examination to determine their fitness for military service from 2008 to 2012. Total alcohol consumption: (1) in the week preceding (habitual/typical) the visit (recent alcohol intake), (2) in a typical week and (3) frequency of 'binge drinking' (consuming more than 5 units/day)) in the past 30 days was estimated.

MAIN OUTCOME MEASURES

Semen quality (volume, sperm concentration, total sperm count, and percentages of motile and morphologically normal spermatozoa) and serum concentration of reproductive hormones (follicle-stimulating hormone, luteinising hormone, testosterone, sex hormone binding globulin, oestradiol, free testosterone and inhibin B).

RESULTS

Sperm concentration, total sperm count and percentage of spermatozoa with normal morphology were negatively associated with increasing habitual alcohol intake. This association was observed in men reporting at least 5 units in a typical week but was most pronounced for men with a typical intake of more than 25 units/week. Men with a typical weekly intake above 40 units had a 33% (95% CI 11% to 59%) reduction in sperm concentration compared to men with an intake of 1-5 units/week. A significant increase in serum free testosterone with increasing alcohol consumption the week preceding the visit was found. Binging was not independently associated with semen quality.

CONCLUSIONS

Our study suggests that even modest habitual alcohol consumption of more than 5 units per week had adverse effects on semen quality although most pronounced associations were seen in men who consumed more than 25 units per week. Alcohol consumption was also linked to changes in testosterone and SHBG levels. Young men should be advised to avoid habitual alcohol intake.

Alcohol and male reproductive health: a cross-sectional study of 8344 healthy men from Europe and the USA

STUDY QUESTION

Is there an association between alcohol intake and semen quality and serum reproductive hormones among healthy men from the USA and Europe?

SUMMARY ANSWER

Moderate alcohol intake is not adversely associated with semen quality in healthy men, whereas it was associated with higher serum testosterone levels.

WHAT IS KNOWN ALREADY

High alcohol intake has been associated with a wide range of diseases. However, few studies have examined the correlation between alcohol and reproductive function and most have been conducted in selected populations of infertile men or have a small sample size and the results have been contradictory.

STUDY DESIGN, SIZE, DURATION

A coordinated international cross-sectional study among 8344 healthy men. A total of 1872 fertile men aged 18-45 years (with pregnant partners) from four European cities and four US states, and 6472 young men (most with unknown fertility) aged 18-28 years from the general population in six European countries were recruited.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The men were recruited using standardized protocols. A semen analysis was performed and men completed a questionnaire on health and lifestyle, including their intake of beer, wine and liquor during the week prior to their visit. Semen quality (semen volume, sperm concentration, percentage motile and morphologically normal sperm) and serum reproductive hormones (FSH, LH, testosterone, sex hormone-binding globulin, and inhibin B and free testosterone) were examined.

MAIN RESULTS AND THE ROLE OF CHANCE

The participation rate for our populations was 20-30%. We found no consistent association between any semen variable and alcohol consumption, which was low/moderate in this group (median weekly intake 8 units), either for total consumption or consumption by type of alcohol. However, we found a linear association between total alcohol consumption and total or free testosterone in both groups of men. Young and fertile men who consumed >20 units of alcohol per week had, respectively, 24.6 pmol/l (95% confidence interval 16.3-32.9) and 19.7 pmol/l (7.1-32.2) higher free testosterone than men with a weekly intake between 1 and 10 units. Alcohol intake was not significantly associated with serum inhibin B, FSH or LH levels in either group of men. The study is the largest of its kind and has sufficient power to detect changes in semen quality and reproductive hormones.

LIMITATIONS, REASONS FOR CAUTION

The participation rate was low, but higher than in most previous semen quality studies. In addition, the study was cross-sectional and the men were asked to recall their alcohol intake in the previous week, which was used as a marker of intake up to 3 months before. If consumption in that week differed from the typical weekly intake and the intake 3 months earlier, misclassification of exposure may have occurred. However, the men were unaware of their semen quality when they responded to the questions about alcohol intake. Furthermore, we cannot exclude that our findings are due to unmeasured confounders, including diet, exercise, stress, occupation and risk-taking behavior.

WIDER IMPLICATIONS OF THE FINDINGS

Our study suggests that moderate alcohol intake is not adversely associated with semen quality in healthy men, whereas it was associated with higher serum testosterone levels which may be due to a changed metabolism of testosterone in the liver. Healthy men may therefore be advised that occasional moderate alcohol intake may not harm their reproductive health; we cannot address the risk of high alcohol consumption of longer duration or binge drinking on semen quality and male reproductive hormones.

STUDY FUNDING/COMPETING INTERESTS

All funding sources were non-profitable and sponsors of this study played no role in the study design, in data collection, analysis, or interpretation, or in the writing of the article. The authors have no conflicts of interest.

The office visit

This article summarizes the current office-based evaluation of male infertility and offers speculation, based on current research, on the future evolution of this encounter. A comprehensive history, physical examination, and semen analysis remain paramount to directing the evaluation; however, new advances continue to refine diagnostic and treatment algorithms. Interpretation of the routine semen analysis as well as adjunctive assessments, including reactive oxygen species, DNA fragmentation, and fluorescent in situ hybridization (FISH) are discussed. The analysis of genetic and endocrine abnormalities is reviewed.

Maternal caffeine consumption has irreversible effects on reproductive parameters and fertility in male offspring rats

OBJECTIVE

Concerns are growing about the decrease in male reproductive health. Caffeine is one of the popular nutrients that has been implicated as a risk factor for infertility. In the present study, we examined whether in utero and lactational exposure to caffeine affects the reproductive function of the offspring of rats.

METHODS

Pregnant rats received caffeine via drinking water during gestation (26 and 45 mg/kg) and lactation (25 and 35 mg/kg). Body and reproductive organ weight, seminiferous tubule diameter, germinal epithelium height, sperm parameters, fertility rate, number of implantations, and testosterone level of the offspring were assessed from birth to adulthood.

RESULTS

Significant dose-related decreases were observed in the body and reproductive organ weight, seminiferous tubule diameter, and germinal epithelium height of the offspring. Sperm density had declined significantly in offspring of the low-dose and high-dose groups, by 8.81% and 19.97%, respectively, by postnatal day 150. The number of viable fetuses had decreased significantly in females mated with male offspring of the high-dose group at postnatal days 60, 90, 120, and 150. There were also significant reductions in testosterone levels of high-dose group offspring from birth to postnatal day 150.

CONCLUSION

It is concluded that maternal caffeine consumption impairs gonadal development and has long-term adverse effects on the reproductive efficiency of male offspring rats.

Does last week's alcohol intake affect semen quality or reproductive hormones? A cross-sectional study among healthy young Danish men

The association between last 5 days of alcohol intake, semen quality and reproductive hormones was estimated in this cross-sectional study among 347 men. Conventional semen characteristics, DNA fragmentation index and reproductive hormones (testosterone, estradiol, sex hormone-binding globulin (SHBG), follicle-stimulating hormone (FSH), luteinizing hormone (LH) and inhibin B) were determined. There was a tendency towards lower semen characteristics at higher intake of alcohol past 5 days, albeit with no statistically significant dose-response association. The ratio between free estradiol and free testosterone was higher at higher alcohol intake during the 5 days preceding semen sampling. In conclusion, alcohol intake was associated with impairment of most semen characteristics but without a coherent dose-response pattern. The study indicates an association between recent alcohol intake and a hormonal shift towards higher estradiol/testosterone ratio. The hormonal changes observed may over time, lead to adverse effects on semen quality, but longitudinal studies are needed to study this.

Focus issue on male infertility

Male infertility problems can occur when sperms are limited in number or function. In this paper, we describe the clinical evaluation of male infertility. A detailed history, physical examination, and basic semen analysis are required. In addition, ultrasound, karyotyping, and hormonal studies are needed to determine specific causes of infertility. In addition, the World Health Organization (WHO, 2009) has developed a manual to provide guidance in performing a comprehensive semen analysis. Among the possible reasons for male infertility, nonobstructive azoospermia is the least treatable, because few or no mature sperm may be produced. In many cases, men with nonobstructive azoospermia typically have small-volume testes and elevated FSH. Although treatment may not completely restore the quality of semen from men with subnormal fertility, in some cases a successful pregnancy can still be achieved through assisted reproductive technology.

Alcohol, drugs, caffeine, tobacco, and environmental contaminant exposure: reproductive health consequences and clinical implications

Reproductive function and fertility are thought to be compromised by behaviors such as cigarette smoking, substance abuse, and alcohol consumption; however, the strength of these associations are uncertain. Furthermore, the reproductive system is thought to be under attack from exposure to environmental contaminants, particularly those chemicals shown to affect endocrine homeostasis. The relationship between exposure to environmental contaminants and adverse effects on human reproductive health are frequently debated in the scientific literature and these controversies have spread into the lay press drawing increased public and regulatory attention. Therefore, the objective of the present review was to critically evaluate the literature concerning the relationship between lifestyle exposures and adverse effects on fertility as well as examining the evidence for a role of environmental contaminants in the purported decline of semen quality and the pathophysiology of subfertility, polycystic ovarian syndrome, and endometriosis. The authors conclude that whereas cigarette smoking is strongly associated with adverse reproductive outcomes, high-level exposures to other lifestyle factors are only weakly linked with negative fertility impacts. Finally, there is no compelling evidence that environmental contaminants, at concentrations representative of the levels measured in contemporary biomonitoring studies, have any effect, positive or negative, on reproductive health in the general population. Further research using prospective study designs with robust sample sizes are needed to evaluate testable hypotheses that address the relationship between exposure and adverse reproductive health effects.

Health and life style among infertile men and women

OBJECTIVE

Lifetime prevalence of infertility among couples is approximately 10-15%, but studies addressing their health behavior are few. Our aim was to describe health and life style of Finnish men and women who had experienced infertility.

DESIGN

Cross-sectional survey.

SETTING

Finland.

POPULATION AND METHODS

Data from a population-based survey (n=7021) was utilized. Life style of infertile men (n=289) and women (n=155) were compared to other men and fertile women.

MAIN OUTCOME MEASURES

Life style (dietary factors, use of alcohol, physical activity), reproductive factors, other diseases and symptoms.

RESULTS

After adjusting for age, area and education, infertile women under 50 years consumed more polyunsaturated fat (OR 1.23, 95% CI 1.03-1.46), less saturated fat (OR 0.83, 95% CI 0.74-0.92) and had experienced more hangovers during previous year (OR 1.02, 95% CI 1.00-1.05) than fertile women. Infertile men under 50 years consumed more total fat (OR 1.06, 95% CI 1.03-1.10), polyunsaturated fat (OR 1.20, 95% CI 1.05-1.37) and monounsaturated fat (OR 1.17, 95% CI 1.06-1.28) compared to other men. Infertile men did not consume more alcohol nor smoke more cigarettes but reported more often allergies than fertile men. Infertile women also had Chlamydia trachomatis infection, benign tumor in their uterus and intestinal disease more often than fertile women. Infertile women over 50 years were more often current smokers than fertile women, but the differences in other age-groups were not significant.

CONCLUSIONS

Women with infertility experience reported more diseases and less use of oral contraceptives than other women, possibly reflecting reasons to infertility. Since both infertility and unhealthy use of alcohol are an increasing public health issues in western societies, more attention should be paid towards life style, especially alcohol use of infertile women.

Caffeine intake and semen quality in a population of 2,554 young Danish men

The authors examined the association between semen quality and caffeine intake among 2,554 young Danish men recruited when they were examined to determine their fitness for military service in 2001-2005. The men delivered a semen sample and answered a questionnaire including information about caffeine intake from various sources, from which total caffeine intake was calculated. Moderate caffeine and cola intakes (101-800 mg/day and < or =14 0.5-L bottles of cola/week) compared with low intake (< or =100 mg/day, no cola intake) were not associated with semen quality. High cola (>14 0.5-L bottles/week) and/or caffeine (>800 mg/day) intake was associated with reduced sperm concentration and total sperm count, although only significant for cola. High-intake cola drinkers had an adjusted sperm concentration and total sperm count of 40 mill/mL (95% confidence interval (CI): 32, 51) and 121 mill (95% CI: 92, 160), respectively, compared with 56 mill/mL (95% CI: 50, 64) and 181 mill (95% CI: 156, 210) in non-cola-drinkers, which could not be attributed to the caffeine they consumed because it was <140 mg/day. Therefore, the authors cannot exclude the possibility of a threshold above which cola, and possibly caffeine, negatively affects semen quality. Alternatively, the less healthy lifestyle of these men may explain these findings.

EFFECT OF LIFESTYLE FACTORS ONINFERTILITY IN MEN

Environmental factors, changes in lifestyle and occupational exposures are responsible for declining human semen quality. We investigated the effects of history of surgery and lifestyle choices on infertility of 271 infertile men and 251 healthy volunteers. The frequency of varicocelectomy was significantly higher in infertile men (2.9%) than in controls (0.4%; P < 0.05). Alcohol use was significantly more common in infertile men (92%) than in controls (80%; P < 0.01). Satisfaction with sexual life was greater in controls (85%) than in infertile men (77%; P < 0.05). Other factors had no effect.

Cigarette smoking as a cause of delay in conception

Epidemiological studies relating cigarette smoking to the ability to conceive and maintain a pregnancy provide information on the clinical significance of smoking on reproductive health. Cigarette smoking by females has significantly increased in the decades after World War II, and now has an average initiation at ages 18–20 years. Maternal smoking is a hazard to the general health, the reproductive health and the life of both mother and child. Gestational smoking renders the fetus a passive smoker. This can result in fetal and neonatal death and in reduced fecundity of adult daughters.

Effects of environmental tobacco smoke in vivo on rhesus monkey semen quality, sperm function, and sperm metabolism

The objective of this study was to use a non-human primate model to examine the effect of environmental tobacco smoke (ETS) in vivo on semen quality, sperm function, and sperm metabolism. Four adult rhesus macaques (Macaca mulatta) were exposed to ETS for six months, and semen samples were collected every week for evaluation. ETS exposure in vivo did not affect semen quality and sperm function. The sperm X:Y chromosome ratio remained unchanged after ETS exposure. The sex ratio of the embryos fertilized by ETS-exposed males was not different from the control male. However, sperm showed changes in metabolome detected by NMR during the ETS exposure. We concluded that with the duration and level of ETS exposure in this study, semen quality and sperm function were not affected, whereas sperm did undergo metabolic changes with ETS exposure in vivo.

Smoking and reproduction

In the Netherlands, approximately 30% of all women of reproductive age smoke, compared with 36% of men.

Cigarette smoking is associated in women with a dose-related reduction in fecundity and fertility and in men with a reduction in semen quality. Smoking has a negative effect on pregnancy: increased rates of antepartum bleeding and placenta praevia have been described. Smoking is also associated with increases in the rates of spontaneous abortion, low birth weight and perinatal death. Some tobacco-related perinatal deaths are due to an increased risk of serious malformation. Children of mothers who smoke are admitted twice as often to hospital for pulmonary problems. However, studies on maternal smoking and childhood cancer have proved inconclusive.

Semen quality according to prenatal coffee and present caffeine exposure: two decades of follow-up of a pregnancy cohort

BACKGROUND

A few studies have investigated the association between male caffeine consumption in adult life and semen quality with conflicting results, but so far no studies have explored the effect of prenatal coffee exposure. We studied the association between prenatal coffee and current caffeine exposure and semen quality and levels of reproductive hormones.

METHODS

From a Danish pregnancy cohort established in 1984-1987, 347 sons out of 5109 were selected for a follow-up study conducted 2005-2006. Semen and blood samples were analyzed for conventional semen characteristics and reproductive hormones and were related to information on maternal coffee consumption during pregnancy and present caffeine consumption. Data were available for 343 men.

RESULTS

There was a tendency toward decreasing crude median semen volume (P = 0.06) and adjusted mean testosterone (P = 0.06) and inhibin B (P = 0.09) concentrations with increasing maternal coffee consumption during pregnancy. Sons of mothers drinking 4-7 cups/day had lower testosterone levels than sons of mothers drinking 0-3 cups/day (P = 0.04). Current male caffeine intake was associated with increasing testosterone levels (P = 0.007). Men with a high caffeine intake had approximately 14% higher concentration of testosterone than those with a low caffeine intake (P = 0.008).

CONCLUSIONS

The results observed in this study are only tentative, but they do not exclude a small to moderate effect of prenatal coffee exposure on semen volume and levels of reproductive hormones. Present adult caffeine intake did not show any clear associations with semen quality, but high caffeine intake was associated with a higher testosterone concentration.

Is smoking a risk factor for decreased semen quality? A cross-sectional analysis

BACKGROUND

Previous studies suggest a deleterious effect of cigarette smoking on semen quality, but their results have not been consistent. We studied the association between current smoking and semen characteristics and hormonal levels in a large group of healthy men.

METHODS

From 1987 to 2004, seven separate occupational or environmental semen quality studies were co-ordinated by our department. A total of 2562 men participated, each providing semen and blood sample and answering a questionnaire about lifestyle and factors related to health. Appropriate semen and smoking data were available for 2542 men.

RESULTS

Adjusting for study, age and other covariates, we observed an inverse dose-response relation between smoking and semen volume, total sperm count and percentage motile sperm. Heavy smokers had a 19% lower sperm concentration than non-smokers. We found a positive dose-response relationship between smoking and testosterone, LH and the LH/free testosterone ratios.

CONCLUSION

Current smoking in adult life moderately impairs the semen quality. It is well known that semen quality is associated to fecundity. Therefore, it would be sensible to advise men to abstain from smoking to avoid decreased fecundity.

Effect of lifestyle exposures on sperm aneuploidy

Lifestyle exposures including cigarette smoke, alcohol, and caffeine have all been studied in relationship to male reproductive health. Over the years the focus has primarily been on semen quality and/or fertility. More recently, literature evaluating direct adverse effects of lifestyle exposures on sperm chromosomes and chromatin has grown due to concern that induced damage could be transmitted to offspring causing transgenerational health effects. In this paper we present a new analysis that summarizes published studies of smoking effects on sperm chromosome number and demonstrates a statistically significant increase in sperm disomy among smokers compared to nonsmokers (P < 0.001). In addition, new data on the effect of alcohol intake on sperm chromosome number are presented showing a rate ratio of 1.38 (95% CI 1.2, 1.6) for XY frequency in sperm of alcohol drinkers compared to nondrinkers.

The male reproductive system and its susceptibility to endocrine disrupting chemicals

In the past years, there has been increased interest in assessing the relationship between impaired male fertility and environmental factors. Human male fertility is a complex process and therefore a great variety of sites may be affected by exogenous noxae. Lifestyle factors as well as various environmental and occupational agents may impair male fertility. Many studies have been published reporting on reproductive dysfunctions in male animals and humans. Especially environmental pollutants with endocrine activity are discussed as a possible cause of this detrimental development. Evidence from animal experiments show that substances with oestrogenic and antiandrogenic properties may cause hypospadia, cryptorchidism, reduction of sperm density and an increase of testicular tumours. Many adverse effects on animal male fertility have been documented for phthalates and some chlorinated hydrocarbons such as polychlorinated biphenyls and polychlorinated dibenzo-p-dioxins. For other chemicals such as bisphenol A and nonylphenols animal data are conflicting. Environmental pollutants may mediate their effects by receptor binding, modulation of hormone-regulated mechanisms or direct toxic effects. Data on environmental chemicals and human male fertility are scarce, and risk assessment is mostly based on the results of animal studies. However, there are indications that exposure to endocrine active chemicals during early development may alter hormone responsiveness in adulthood. Furthermore, some of the chemicals are found in fluids that are associated with human reproduction, such as follicular fluid, seminal fluid and cervical mucus. Recent studies suggest a correlation between pesticide exposure and standard semen parameters as well as in vitro fertilization rates.

Sperm preparation for ART

The onset of clinical assisted reproduction, a quarter of a century ago, required the isolation of motile spermatozoa. As the indication of assisted reproduction shifted from mere gynaecological indications to andrological indications during the years, this urged andrological research to understand the physiology of male germ cell better and develop more sophisticated techniques to separate functional spermatozoa from those that are immotile, have poor morphology or are not capable to fertilize oocytes. Initially, starting from simple washing of spermatozoa, separation techniques, based on different principles like migration, filtration or density gradient centrifugation evolved. The most simple and cheapest is the conventional swim-up procedure. A more sophisticated and most gentle migration method is migration-sedimentation. However, its yield is relatively small and the technique is therefore normally only limited to ejaculates with a high number of motile spermatozoa. Recently, however, the method was also successfully used to isolate spermatozoa for intracytoplasmic sperm injection (ICSI). Sperm separation methods that yield a higher number of motile spermatozoa are glass wool filtration or density gradient centrifugation with different media. Since Percoll as a density medium was removed from the market in 1996 for clinical use in the human because of its risk of contamination with endotoxins, other media like IxaPrep, Nycodenz, SilSelect, PureSperm or Isolate were developed in order to replace Percoll. Today, an array of different methods is available and the selection depends on the quality of the ejaculates, which also includes production of reactive oxygen species (ROS) by spermatozoa and leukocytes. Ejaculates with ROS production should not be separated by means of conventional swim-up, as this can severely damage the spermatozoa. In order to protect the male germ cells from the influence of ROS and to stimulate their motility to increase the yield, a number of substances can be added to the ejaculate or the separation medium. Caffeine, pentoxifylline and 2-deoxyadenosine are substances that were used to stimulate motility. Recent approaches to stimulate spermatozoa include bicarbonate, metal chelators or platelet-activating factor (PAF). While the use of PAF already resulted in pregnancies in intrauterine insemination, the suitability of the other substances for the clinical use still needs to be tested. Finally, the isolation of functional spermatozoa from highly viscous ejaculates is a special challenge and can be performed enzymatically to liquefy the ejaculate. The older method, by which the ejaculate is forcefully aspirated through a narrow-gauge needle, should be abandoned as it can severely damage spermatozoa, thus resulting in immotile sperm.

Effects of maternal and paternal alcohol consumption on the success rates of in vitro fertilization and gamete intrafallopian transfer

OBJECTIVE

To determine whether the amount and timing of female and male alcohol use during IVF and GIFT affect reproductive endpoints.

DESIGN

Multicenter prospective study.

SETTING

Clinics in southern California.

PATIENT(S)

Two hundred twenty-one couples with female infertility.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Egg retrieval, transfer, fertilization, pregnancy, miscarriage, live birth, and multiple gestations.

RESULT(S)

Female alcohol consumption was associated with: (1) a 13% decrease in the number of eggs aspirated (adjusted 95% confidence interval [CI]: -2% to -23%, for one additional drink per day, 1 year before the IVF or GIFT attempt); (2) an increase in risk of not achieving pregnancy by 2.86 times (0.99-8.24, 1 month prior); and (3) an increase in risk of miscarriage by 2.21 times (1.09-4.49, 1 week before the procedure). For men, one additional drink per day increased the risk of not achieving a live birth by 2.28 (1.08-4.80) to 8.32 (1.82-37.97) times, depending on the time period; beer also affected live births (ORs = 5.49-45.64). This outcome may be due partially to increased risk of miscarriage by 2.70 to 38.04 times for men who drank <or=1 month before and during IVF and GIFT.

CONCLUSION(S)

This is the first study to report an association between alcohol use and reproductive endpoints of IVF and GIFT. Because alcohol use is ubiquitous, modifying drinking habits may increase assisted reproductive technology success rates.

Effects of caffeine on human health

Caffeine is probably the most frequently ingested pharmacologically active substance in the world. It is found in common beverages (coffee, tea, soft drinks), in products containing cocoa or chocolate, and in medications. Because of its wide consumption at different levels by most segments of the population, the public and the scientific community have expressed interest in the potential for caffeine to produce adverse effects on human health. The possibility that caffeine ingestion adversely affects human health was investigated based on reviews of (primarily) published human studies obtained through a comprehensive literature search. Based on the data reviewed, it is concluded that for the healthy adult population, moderate daily caffeine intake at a dose level up to 400 mg day(-1) (equivalent to 6 mg kg(-1) body weight day(-1) in a 65-kg person) is not associated with adverse effects such as general toxicity, cardiovascular effects, effects on bone status and calcium balance (with consumption of adequate calcium), changes in adult behaviour, increased incidence of cancer and effects on male fertility. The data also show that reproductive-aged women and children are 'at risk' subgroups who may require specific advice on moderating their caffeine intake. Based on available evidence, it is suggested that reproductive-aged women should consume </=300 mg caffeine per day (equivalent to 4.6 mg kg(-1) bw day(-1) for a 65-kg person) while children should consume </=2.5 mg kg(-1) bw day(-1).

Comprehensive office evaluation in the new millennium

The success of a comprehensive office-based evaluation of male-factor infertility depends on the physician's thorough understanding of risk assessment in the history, identification of pertinent physical examination findings, and correct assessment of laboratory data. Office-based ultrasonographic techniques have already increased the urologist's ability to visualize suspected anatomic abnormalities, and the use of functional tests of sperm has given greater depth to the limited, but essential, prognostic capabilities of the routine semen analysis.

Individualized homeopathic therapy for male infertility

This prospective observational pilot study investigated the effect of individualized homeopathy on male infertility based on sperm count, hormone values and general health. Forty-five subfertile men were treated with single homeopathic remedies for an average of 10.3 months. The drugs were prescribed on the basis of the overall symptomatic situation. The variables 'sperm density', 'percentage of sperm with good progressive motility' and 'density of sperm with good propulsive motility' improved significantly, especially in cases of oligoasthenozoospermia. The general health of patients improved significantly. The following factors emerged as positive predictors of therapy success: alcohol consumption below 30 g/day, non-smoking, the presence of less than five dental amalgam fillings, no exposure to noxious substances at the workplace and no previous inflammatory genital diseases. The factors stress, age above 36, high coffee consumption and long duration of unwanted childlessness did not have a negative impact on therapy outcome in this study. The rate of improvement in sperm count through homeopathic therapy is comparable to the improvement achieved by conventional therapy, so that individualized-homeopathic treatment may be considered a useful alternative to conventional treatment of subfertile men. For further investigation, a randomised, therapy-controlled clinical study with parallel group design would be useful (homeopathic therapy vs conventional andrological therapy).

A prospective study of the effects of female and male caffeine consumption on the reproductive endpoints of IVF and gamete intra-Fallopian transfer

BACKGROUND

This study evaluated the timing and amount of caffeine intake by women and men undergoing IVF and gamete intra-Fallopian transfer (GIFT) on oocyte retrieval, sperm parameters, fertilization, multiple gestations, miscarriage, and live births.

METHODS

A prospective study of 221 couples was conducted in Southern California between 1993 and 1998. "Usual" caffeine intake during lifetime and 1 year prior to attempt, caffeine intake during the week of the initial clinic visit, as well as intake during the week of the procedure, was evaluated from beverages (coffee, soda, tea) and chocolates.

RESULTS

Not achieving a live birth was significantly associated with "usual" female caffeine consumption [adjusted odds ratios (95% confidence intervals): 3.1 (1.1, 9.7) and 3.9 (1.3, 11.6) for intake of >2-50 and 50 mg/day, compared with 0-2 mg/day] and consumption during the week of the initial visit [2.9 (1.1, 7.5) and 3.8 (1.4, 10.7)] female compared with 0-2 mg/day, although caffeine use was low. Infant gestational age decreased by 3.8 (-6.9, -0.7) or 3.5 (-6.7, -0.3) weeks for women who consumed >50 mg/day of caffeine "usually" or during the week of the initial visit. The odds of having multiple gestations increased by 2.2 (1.1, 4.4) and 3.0 (1.2, 7.4) for men who increased their "usual" intake or intake during the week of the initial visit by an extra 100 mg/day. Caffeine intake was not significantly associated with other outcomes.

CONCLUSIONS

This is the first IVF/GIFT study to report any effect of caffeine on live births, gestational age, and multiple gestations. If these findings are replicated, caffeine use should be minimized prior to and while undergoing IVF/GIFT.

Substance abuse and parenthood: biological mechanisms--bioethical challenges

This review catalogues the long-term health effects of parental recreational drug abuse on the fetus and the subsequent well-being of the child. It is hard to conceive that parents would knowingly harm the health of their children, yet toxic effects resulting from ignorance, addiction or any of a number of socioeconomic factors are still responsible for handicapping countless potentially healthy offspring. The negative effects of female recreational drug and alcohol abuse during pregnancy are well documented, but exposure prior to conception and male-mediated effects are less well publicized. Abnormalities in the sperm are prevalent among men who consume recreational drugs, and birth defects are more often linked with paternal than with maternal DNA damage. This review is divided into three parts. Part I describes the biology and potential mechanisms of adverse alterations in reproductive potential, Part II explores the socioeconomic determinants of substance use, and raises the question of poverty. Drug-induced disability is not evenly distributed among the population as there are ethnic and socioeconomic disparities of infant mortality, childhood morbidity and reproductive dysfunction. Part III describes the author's conclusion that fundamental social change is needed to protect future children without threatening parents' basic freedom, and real change requires new beliefs and prioritics that must evolve from the ground up. An ecological model of care concentrating on health issues is described. Such an ecological model of care is in tune with the fundamental principles of bioscience ethics and emphasises that high quality education, health and good preconceptional/prenatal care are essentials in the search for greater equity in standard of living across a population.

In vitro tests for essential sperm functions using the phyto-oestrogen genistein as a test substance

Sperm motility, binding of spermatozoa to the zona pellucida and induction of the acrosome reaction are prerequisites for successful oocyte fertilization. Examination of the physiological and nonphysiological effects of particular compounds on sperm functions requires high-quality in vitro test systems. In this short methodological overview, a reliable combined in vitro test system with bovine gametes is described. The purpose of the study was to evaluate whether aliquots of pooled post-thaw spermatozoa are suitable for examination of environmental substances that affect essential sperm functions. The combined test system includes a number of known methods for the assessment of sperm vitality and motion parameters, acrosomal status, inducibility of acrosome reaction and sperm zona pellucida binding. First observations indicate that genistein inhibits the induction of acrosomal exocytosis and binding of spermatozoa to the zona pellucida. Motility parameters and the viability of bovine spermatozoa were not affected by this substance. It is concluded that genistein, a phyto-oestrogen which is abundant in several plants, can be used as a test substance for the evaluation of effects upon essential bovine sperm functions in vitro.

Smoking cigarettes is associated with increased sperm disomy in teenage men

OBJECTIVE

To determine whether moderate cigarette smoking and alcohol consumption in teenage men is associated with increases in disomic sperm and detectable changes in semen quality.

DESIGN

Cohort study.

SETTING

Military recruiting station, Teplice, Czech Republic.

PATIENT(S)

Ten current smokers (20 cigarettes per day for at least 2 years, exposure confirmed by urine cotinine) who also consumed alcohol and 15 nonsmokers. All patients were exactly 18 years old, healthy, and of unproven fertility.

MAIN OUTCOME MEASURE(S)

Sperm aneuploidy by multicolor fluorescence in situ hybridization for chromosomes 8, X, and Y; conventional semen analyses; computer-aided sperm analysis for motility; and sperm chromatin structure analysis.

RESULTS

Smokers showed elevated frequencies of sperm aneuploidy (Y disomy, P <0.001; aggregate of X, Y, and 8 disomies, P <0.01); reduced linearity of sperm motion (P <0.05); and more "round-headed" sperm (P <0.01). Smokers' semen contained fewer sperm (P <0.001) and fewer motile sperm (P <0.02), which was attributable, in part, to shorter abstinence intervals among smokers (P <0.02).

CONCLUSION(S)

Cigarette smoking among teenagers was associated with increases in disomic sperm and a diminution in specific aspects of semen quality. Such defects may affect male fertility and may increase future chances of fathering offspring with aneuploidy syndromes.

Effects of cigarette smoking on semen characteristics of a population in Mexico

A study of semen quality was conducted in 197 smoking and 161 non-smoking men undergoing initial infertility investigation. The men were allocated into groups according the number of cigarettes smoked per day < 10 (n = 57), 11-20 (n = 115), and > 20 cigarettes (n = 25). Smokers had significantly poorer sperm density (P < .005), a lower percentage of viability (P < .007), a lower percentage of normal sperm morphology (P < .005), and the percentage of motile sperm was lower (P < .005). These parameters were worse in the heavy smoking groups. Thus the present study corroborates reports of detrimental effects of cigarette smoking on sperm characteristics. Further studies are needed to explain the mechanism by which smoking affects spermatogenesis.

Use of fluorescence in situ hybridization (FISH) to assess effects of smoking, caffeine, and alcohol on aneuploidy load in sperm of healthy men

Aneuploidy is a common cause of poor reproductive outcomes in humans and is associated with severe medical problems in liveborn offspring, yet little is known about its underlying cause. A substantial amount of aneuploidy is known to be contributed by the father through cytogenetically abnormal sperm. The purpose of this cross-sectional, observational study was to investigate the potential contribution of common lifestyle exposures (smoking, caffeine, and alcohol) to the aneuploidy load in sperm from 45 healthy male volunteers 19-35 years of age. Sperm FISH (fluorescence in situ hybridization) was used to determine aneuploidy and diploidy frequencies for chromosomes X, Y and 18 across varying exposure levels of smoking, caffeine, and alcohol. Caffeine was significantly associated with increased frequencies of sperm aneuploidy XX18 and XY18, diploidy XY18-18 and the duplication phenotype YY18-18 controlling for alcohol, smoking and donor age. Alcohol was significantly associated with increased frequencies of sperm aneuploidy XX18, diploidy XY18-18 and the duplication phenotype XX18-18 controlling for caffeine, smoking and donor age. There was a suggestive, but unstable, association between smoking and XX18. Even within our truncated age range, we were able to confirm an increased risk for XX18 aneuploidy with increasing donor age. Sperm FISH proved to be a useful biomarker to detect and compare numerical cytogenetic abnormalities in human sperm cells across differing levels of exposure to smoking, caffeine, and alcohol.

Smoking and male reproduction: a review

Because of the large number of men worldwide who smoke and the fact that cigarette smoke contains known mutagens and carcinogens, there has been concern that smoking may have adverse effects on male reproduction. A review of the epidemiological literature indicates that cigarette smoking is associated with modest reductions in semen quality including sperm concentration, motility and morphology. The associations between male smoking and sperm concentration and motility are stronger among studies of 'healthy' men (e.g. volunteers and sperm donors) than among men from infertility clinic populations. Smoking has also been associated with alterations in hormone levels in males, for example increases in the levels of oestrone and oestradiol. Despite modest reductions in semen quality and altered hormone levels among smokers compared to non-smokers, studies have not shown a reduction in male fertility in association with paternal smoking. There is some evidence to suggest that paternal smoking is associated with congenital anomalies and childhood cancer (with ORs in positive studies generally < 2.0). Smoking has not been shown to be mutagenic to human spermatozoa, although studies have been small and have had methodological shortcomings. It is concluded that, although smokers as a group may not experience reduced fertility, men with marginal semen quality who wish to have children may benefit from quitting smoking, since several small studies indicate the potential for improved semen quality after quitting smoking. More research on the benefits of quitting smoking among men with marginal semen quality is needed. Methodological improvements in studies aimed at clarifying the association between paternal smoking and reproductive and developmental outcomes in offspring should include obtaining accurate paternal smoking dose information, evaluating smoking exposure information in relation to various time windows (e.g. prior to conception, during gestation), and controlling for potential confounders and modifying factors such as age and maternal smoking habits. More sensitive and specific laboratory assays and increased sample sizes are required to establish whether smoking induces mutations in human spermatozoa.

Cigarette smoking and semen quality

OBJECTIVE

To determine whether cotinine levels provide stronger evidence for an association between smoking and semen quality than the number of cigarettes smoked per day or years smoked controlling for potential confounders and effect modifiers.

DESIGN

Cross-sectional study.

SETTING

Male volunteers at the Reproductive Endocrinology-Fertility Laboratory.

PARTICIPANTS

Eighty-eight men (ages 18 to 35 years) provided a semen, urine, and blood specimen and completed a self-administered questionnaire concerning smoking and demographic information as well as caffeine and alcohol consumption. Urine, blood, and semen cotinine levels were analyzed via RIA.

MAIN OUTCOME MEASURE

Standard clinical semen analysis.

RESULTS

Number of cigarettes smoked per day, years smoked, and log-transformed cotinine levels were associated negatively with semen quality (density, total count, and motility). The association was evident among men age > or = 22 years. For example, the correlation coefficient for the overall association between logged urine cotinine and logged sperm density was -0.23; those stratified by age were 0. 13 (age < 22 years) and - 0. 39 (age > or = 22 years). Potential confounders included in regression models did not diminish the associations.

CONCLUSIONS

Smoking is associated with lowered semen quality.

High and unchanged sperm counts of Finnish men

Several recent reports have suggested that the sperm counts of normal men are declining in most countries. In this study the sperm counts of Finnish men, and their possible changes during the past 28 years, were investigated. The material consisted of semen samples from 238 normal healthy men of unknown fertility and 5481 men from infertile couples. The means (medians) of semen volume, sperm density and total sperm count in normal men were 3.3 (3.0) ml, 133.9 (94.0) x 10(6)/ml and 396.6 (309.0) x 10(6), respectively. These parameters and the relative frequency distribution of the sperm density were similar to those reported elsewhere in the 1940s. Multiple linear regression analysis revealed a significant decrease in semen volume, whereas sperm density and total sperm count of infertile men had not changed significantly during the past 28 years. In addition, no change in sperm counts was associated with the year of men's birth.

Effects of nicotine on sperm attachment and penetration of zona-free hamster eggs

A previous study from this laboratory showed that nicotine in vitro has deleterious effects on sperm motion characteristics. This study was conducted to evaluate the effects of nicotine on the ability of human spermatozoa to attach and penetrate zona-free hamster eggs. Spermatozoa from fertile donors, washed free of seminal plasma, were incubated with medium (control) and 0.1, 1, 5, and 10 mM concentrations of nicotine (concentrations estimated to approximate residual concentrations of nicotine in the testes of heavy smokers) for 18 h at 37 degrees C in a humid 5% carbon dioxide incubator. The sperm preparations were then mixed with enzymatically denuded hamster eggs and incubated for 3 h at 37 degrees C. The oocytes were examined by phase-contrast microscopy to enumerate the rates of sperm attachment and penetration. The data were analyzed by a paired t test and repeated measures analysis of variance using the arcsine transformation of the percentages. The percentages of eggs with attached spermatozoa significantly declined in a dose-dependent manner, the highest inhibition being at 10 mM (F = 24). The rate of sperm penetration was even more significantly decreased with the increase in nicotine concentrations in the following order: 10 mM (F = 56) > 5 mM (F = 30) > 1 mM (F = 44) > 0.1 mM (F = 12). Nicotine concentrations of 0.1 mM and above negatively affected sperm penetration of zona-free hamster eggs.

The effect of nicotine on in vitro sperm motion characteristics

PURPOSE AND STUDY PLAN: Men who are habitual smokers tend to have poor semen quality. We studied the effect of nicotine on sperm motility in vitro. Spermatozoa from 13 normal fertile nonsmoking donors, washed free of seminal plasma, were treated with medium alone (control); and, 10 mM, 5 mM, 1 mM and 0.1 mM nicotine (concentrations estimated to approximate residual concentrations of nicotine in the testes of heavy smokers). Computerized sperm motion analysis (CASA) was done at 2, 4, 6 and 24 h after incubation.

RESULTS

Sperm motility, beat/cross frequency, linearity and maximum anterior lateral head displacement (ALH max.) were significantly decreased across nominal dosages (P < 0.001 by repeated measures analysis of variance). Of the concentrations tested, 0.1 mM had no effect; 1 mM significantly decreased sperm motility (P = 0.003) and linearity (P = 0.02); 5 mM decreased the beat frequency (P = 0.001) and linearity (0.02); and 10 mM markedly decreased motility (P = 0.0001), beat frequency (P = 0.0002), linearity (P = 0.02) and ALH max. (P = 0.02). The interactions between dose and time were insignificant.

CONCLUSION

Nicotine at concentrations of > or = 1 mM significantly decreased sperm motion characteristics after different periods of incubation, whereas 0.1 mM concentration had the least effect.

Mutagenic lifestyles? A review of evidence of associations between germ-cell mutations in humans and smoking, alcohol consumption and use of 'recreational' drugs

In humans, associations between germ-cell mutations and hypothetical aetiological factors can be investigated by (1) examining the relationship between the factor of interest and conditions known to be of genetic aetiology; (2) examining the relationship between conditions of unknown aetiology and route of exposure, especially paternal preconceptional exposure. As regards smoking, alcohol and 'recreational' drugs, the first approach has been applied in studies of retinoblastoma, Wilms' tumour and chromosomal anomalies. Only Down's syndrome has received intensive investigation, in relation to maternal smoking during pregnancy; the relative risks would be compatible with there being no association in all recognized conceptuses. The second approach has been applied in studies of sperm quality, miscarriage, congenital anomalies and childhood cancer. The available studies do not show a consistent relationship between smoking and sperm quality; there are few data on the effects of the other exposures. There are a substantial number of studies of childhood cancer and smoking by the father; the majority do not indicate any relationship. Some studies of childhood cancer suggest a positive association with use of 'recreational' drugs by the parents, but it has not been possible to clarify which route of exposure, or the specific type of drug which may be involved. Use of molecular techniques to detect individual genetic changes should enable progress to be made in elucidating the origin of mutation. In the meantime, public health actions are justified on the basis of the known non-genetic effects of these agents.