Use of e-cigarettes associated with lower sperm counts in a cross-sectional study of young men from the general population

STUDY QUESTION

Are use of e-cigarettes and snuff associated with testicular function as previously shown for conventional cigarettes and marijuana?

SUMMARY ANSWER

Use of e-cigarettes is associated with reduced semen quality but not with higher serum testosterone level as observed for conventional cigarette use. Snuff use was not associated with markers of testicular function.

WHAT IS KNOWN ALREADY

Cigarette smoking has previously been associated with higher testosterone levels and impaired semen quality, whereas it is unresolved whether use of e-cigarettes or snuff influence the testicular function.

STUDY DESIGN, SIZE, DURATION

This cross-sectional population-based study included 2008 men with information on cigarette and marijuana use (enrolled between 2012 and 2018), among whom 1221 men also had information on e-cigarette and snuff use (enrolled between 2015 and 2018).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Men (median age 19.0 years) from the general population provided a semen and blood sample and filled out a questionnaire on lifestyle including information on smoking behaviour. Associations between different types of smoking (e-cigarettes, snuff, marijuana and cigarettes) and reproductive hormones (total and free testosterone, sex hormone-binding globulin, LH, oestradiol and ratios of inhibin B/FSH, testosterone/LH and free testosterone/LH) and semen parameters (total sperm count and sperm concentration) were examined using multiple linear regression analyses adjusted for relevant confounders.

MAIN RESULTS AND THE ROLE OF CHANCE

Approximately half of the men (52%) were cigarette smokers, 13% used e-cigarettes, 25% used snuff and 33% used marijuana. Users of e-cigarettes and marijuana were often also cigarette smokers. Compared to non-users, daily e-cigarette users had significantly lower total sperm count (147 million vs 91 million) as did daily cigarette smokers (139 million vs 103 million), in adjusted analyses. Furthermore, significantly higher total and free testosterone levels were seen in cigarette smoking men (6.2% and 4.1% higher total testosterone and 6.2% and 6.2% higher free testosterone in daily smokers and occasional smokers, respectively, compared to non-smoking men), but not among e-cigarette users. Daily users of marijuana had 8.3% higher total testosterone levels compared to non-users. No associations were observed for snuff in relation to markers of testicular function.

LIMITATIONS, REASONS FOR CAUTION

We cannot exclude that our results can be influenced by residual confounding by behavioural factors not adjusted for. The number of daily e-cigarette users was limited and findings should be replicated in other studies.

WIDER IMPLICATIONS OF THE FINDINGS

This is the first human study to indicate that not only cigarette smoking but also use of e-cigarettes is associated with lower sperm counts. This could be important knowledge for men trying to achieve a pregnancy, as e-cigarettes are often considered to be less harmful than conventional cigarette smoking.

STUDY FUNDING/COMPETING INTEREST(S)

Funding was received from the Danish Ministry of Health (1-1010-308/59), the Independent Research Fund Denmark (8020-00218B), ReproUnion (20200407) and the Research Fund of the Capital Region of Denmark (A6176). The authors have nothing to disclose.

TRIAL REGISTRATION NUMBER

NA.

FSHB and FSHR gene variants exert mild modulatory effect on reproductive hormone levels and testis size but not on semen quality: A study of 2020 men from the general Danish population

BACKGROUND

Spermatogenesis depends on stimulation by follicle-stimulating hormone (FSH) which binds to FSH receptors (FSHR) on testicular Sertoli cells. Three FSH-related single-nucleotide polymorphisms (SNPs), FSHB -211G>T (rs10835638), FSHR -29G>A (rs1394205) and FSHR 2039A>G (rs6166) affect FSH action, and have been suggested to affect testicular function, but the evidence is uncertain.

OBJECTIVE

To describe the associations between the three SNPs and testicular function in a large and well-characterised cohort of men from the general population.

MATERIALS AND METHODS

A cross-sectional study of 2020 Danish men unselected regarding testicular function. Outcome variables were semen parameters, reproductive hormones and testis size. Genotyping was done by competitive allele-specific quantitative PCR. Differences in genotype frequencies were tested by chi-square test and associations between genotypes and outcomes were assessed by multivariate linear regressions.

RESULTS

The SNPs affected serum FSH; carriers of the variant affecting FSH secretion (FSHB -211G>T) had lower FSH levels while carriers of variants affecting receptor expression (FSHR -29G>A) and receptor sensitivity (FSHR 2039A>G) had higher FSH levels. Carriers of FSHB -211G>T had lower calculated free testosterone/LH ratio. Although both FSHB -211G>T and FSHR 2039A>G were associated with smaller testis size, no clear association was detected in relation to any semen parameters, except a lower total number of morphologically normal spermatozoa in the heterozygous carriers of the FSHB -211G>T DISCUSSION AND CONCLUSION: The studied polymorphisms have only minor modulating influence on testis size and function in healthy men. We detected subtle effects of the three SNPs on FSH levels, but also effects of FSHB -211G>T on calculated free testosterone/LH ratio, compatible with altered Leydig cell function. Thus, the role of these FSH-related polymorphisms is complex and modest in men with normal testicular function, but the possible importance of FSH polymorphisms in men with impaired testicular function should be evaluated in future studies in more detail.

SAT-045 Free Testosterone and Cardiometabolic Parameters in Adult Men - Comparison of Algorithms for Calculation of Serum Free Testosterone

Context. Determining the free or bioavailable testosterone level has gained increasing interest over the years and different indirect algorithms have been suggested.

Objective. To compare commonly used algorithms of calculation of serum free testosterone, specifically free androgen index (FAI), free testosterone estimated using the Vermeulen algorithm (cFTV) and the Zakharov algorithm (cFTZ) as well as total testosterone in relation to baseline and long-term cardiometabolic conditions.

Design. A prospective cohort study of men participating in four independent population-based surveys (MONICA I-III and Inter99) from 1982 to 2001 and followed until December 2012 with baseline and follow-up information on cardiometabolic parameters.

Setting and Participants. 5350 randomly selected men from the general population aged 30, 40, 50, 60, or 70 years at baseline participated.

Main Outcome Measures. Baseline cardiometabolic parameters and follow-up information on type 2 diabetes, ischemic heart disease, cardiovascular disease mortality, and all-cause mortality.

Results. Free testosterone levels calculated according to the two algorithms differed systematically but however correlated well (cFTV vs. cFTZ: r=0.9, p<0.01) and the relative standard deviations ranged from 37% to 41%. In general, men having cardiometabolic conditions at baseline had lower absolute levels of FAI, cFTV and cFTZ. However, when age-standardizing the hormone levels, FAI levels were higher in this group of men whereas cFTV and cFTZ remained lower compared to men without these conditions. The associations seen for cFTV and cFTZ were in line with the association seen for total testosterone. Cox proportional hazard models revealed that men in the highest quartiles of cFTV or cFTZ had lower risk of developing type 2 diabetes (cFTV: HR=0.74 (0.49-1.10), cFTZ: HR=0.59 (0.39-0.91)) than men in the lowest quartile. In contrast, men with highest levels of FAI had a 74% increased risk of developing type 2 diabetes compared to men in the lowest quartile (HR=1.74, 95% CI:1.17-2.59). In relation to all-cause mortality, FAI showed the strongest inverse association followed by cFTV, whereas cFTZ and total testosterone did not show any association.

Conclusion. Free testosterone estimated by the Vermeulen and Zakharov algorithms differed systematically. However, the computed values correlated well and showed similar associations to baseline and long-term cardiometabolic parameters; albeit with subtle differences. In contrast, an empiric ratio, FAI showed opposite associations to several of the examined parameters and may reflect limited clinical utility.

Average sperm count remains unchanged despite reduction in maternal smoking: results from a large cross-sectional study with annual investigations over 21 years

STUDY QUESTION

How are temporal trends in lifestyle factors, including exposure to maternal smoking in utero, associated to semen quality in young men from the general population?

SUMMARY ANSWER

Exposure to maternal smoking was associated with lower sperm counts but no overall increase in sperm counts was observed during the study period despite a decrease in this exposure.

WHAT IS KNOWN ALREADY

Meta-analyses suggest a continuous decline in semen quality but few studies have investigated temporal trends in unselected populations recruited and analysed with the same protocol over a long period and none have studied simultaneous trends in lifestyle factors.

STUDY DESIGN, SIZE, DURATION

Cross-sectional population-based study including ~300 participants per year (total number = 6386) between 1996 and 2016.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The study is based on men from the Greater Copenhagen area, Denmark, with a median age of 19 years, and unselected with regard to fertility status and semen quality. The men delivered a semen sample, had a blood sample drawn and a physical examination performed and answered a comprehensive questionnaire, including information on lifestyle and the mother's pregnancy. Temporal trends in semen quality and lifestyle were illustrated graphically, and trends in semen parameters and the impact of prenatal and current lifestyle factors were explored in multiple regression analyses.

MAIN RESULTS AND THE ROLE OF CHANCE

Throughout the study period, 35% of the men had low semen quality. Overall, there were no persistent temporal trends in semen quality, testicular volume or levels of follicle-stimulating hormone over the 21 years studied. The men's alcohol intake was lowest between 2011 and 2016, whereas BMI, use of medication and smoking showed no clear temporal trends. Parental age increased, and exposure in utero to maternal smoking declined from 40% among men investigated in 1996-2000 to 18% among men investigated in 2011-2016. Exposure to maternal smoking was associated with lower sperm counts but no overall increase in sperm counts was observed despite the decrease in this exposure.

LIMITATIONS, REASONS FOR CAUTION

Information of current and prenatal lifestyle was obtained by self-report, and the men delivered only one semen sample each.

WIDER IMPLICATIONS OF THE FINDINGS

The significant decline in in utero exposure to maternal smoking, which was not reflected in an overall improvement of semen quality at the population level, suggest that other unknown adverse factors may maintain the low semen quality among Danish men.

STUDY FUNDING/COMPETING INTEREST(S)

The study has received financial support from the ReproUnion; the Research fund of Rigshospitalet, Copenhagen University Hospital; the European Union (Contract numbers BMH4-CT96-0314,QLK4-CT-1999-01422, QLK4-CT-2002-00603, FP7/2007-2013, DEER Grant agreement no. 212844); the Danish Ministry of Health; the Danish Environmental Protection Agency; A.P. Møller and wife Chastine McKinney Møllers foundation; and Svend Andersens Foundation. None of the funders had any role in the study design, collection, analysis or interpretation of data, writing of the paper or publication decisions.

TRIAL REGISTRATION NUMBER

N/A.

Semen Quality as a Predictor of Subsequent Morbidity: A Danish Cohort Study of 4,712 Men With Long-Term Follow-up

Semen quality has been suggested to be a biological marker of long-term morbidity and mortality; however, few studies have been conducted on this subject. We identified 5,370 men seen for infertility at Frederiksberg Hospital, Denmark, during 1977-2010, and 4,712 of these men were followed in the Danish National Patient Registry until first hospitalization, death, or the end of the study. We classified patients according to hospitalizations and the presence of cardiovascular disease, diabetes, testicular cancer, or prostate cancer. We found a clear association between sperm concentration below 15 million/mL and all-cause hospitalizations (hazard ratio = 1.5, 95% confidence interval: 1.4, 1.6) and cardiovascular disease (hazard ratio = 1.4, 95% confidence interval: 1.2, 1.6), compared with men with a concentration above 40 million/mL. The probabilities for hospitalizations were also higher with a low total sperm count and low motility. Men with a sperm concentration of 195-200 million/mL were, on average, hospitalized for the first time 7 years later than were men with a sperm concentration of 0-5 million/mL. Semen quality was associated with long-term morbidity, and a significantly higher risk of hospitalization was found, in particular for cardiovascular diseases and diabetes mellitus. Our study supports the suggestion that semen quality is a strong biomarker of general health.

Reference ranges of 17-hydroxyprogesterone, DHEA, DHEAS, androstenedione, total and free testosterone determined by TurboFlow-LC-MS/MS and associations to health markers in 304 men

We report reference ranges based on LC-MS/MS for testosterone (T), free testosterone (FT) and its precursors, i.e. 17-hydroxyprogesterone (17-OHP), dehydroepiandrosterone (DHEA), DHEA-sulfate (DHEAS) and androstenedione (Adione), in relation to different health markers and lifestyle factors. The study was based on 304 healthy men aged 30-61 years participating in a population-based cross-sectional study (Health2008). Examination program consisted of a clinical examination, completion of a self-administered questionnaire and blood sampling. Steroid metabolites were measured by a validated and sensitive LC-MS/MS method. Older age-groups were significantly associated with decreased concentrations of DHEA, DHEAS, Adione, and FT, while no significant associations with age were shown for 17-OHP or T. Participants with BMI≥30 kg/m(2) had lower age-related steroid metabolite z-scores compared to participants with BMI<30 kg/m(2), i.e. 17-OHP: -0.51 vs. 0.08 (p<0.001); DHEA: -0.27 vs. 0.09 (p=0.014); Adione: -0.29 vs. 0.09 (p=0.012); T: -0.99 vs. 0.14 (p<0.001); and FT -0.55 vs. 0.05 (p<0.001), respectively. In conclusion, this large study on serum steroid metabolites and concomitant assessment of health markers in healthy men provides age-related reference ranges, and furthermore evaluates the impact of lifestyle factors and metabolic syndrome on androgen metabolite levels.