Infertility is the inability to conceive after 1 year of unprotected sexual intercourse.[1–4] Male factor infertility alone accounts for about 30% to 50% of the infertile couples. In Beijing (China), the prevalence of couple infertility is around 4.2%. Risk factors for male infertility are many and include obstructive, genetic, endocrine, and occupational risk factors, as well as age, diet, and ejaculatory disorders.
A varicocele is a vascular lesion characterized by dilation of gonadal veins in the scrotum, sometimes described as having a “bag of worms” appearance. Varicoceles are most frequent at the beginning of puberty and are found in 14% to 20% of adolescents and adults.[4,6] Varicoceles may lead to elevated scrotal temperature, which impairs spermatogenesis, for which optimal temperature is typically 33°C to 34°C. Varicoceles are easily corrected by surgery, restoring proper scrotal temperature and fertility.[6,8,9]
The prevalence of varicoceles is about 15% to 20% in the general population, but the prevalence is 30% to 40% among patients with infertility. The prevalence of varicoceles increases with age and the risk of varicoceles increases by about 10% for each decade of life. Nevertheless, even if the association of varicoceles with infertility is well established, the exact effect of varicoceles on semen quality among patients with infertility is still poorly known and studies are limited by a small sample size.[12,13] In addition, far from all, men with a varicocele are infertile. The incidence of varicocele ranges from 35% to 40% in men with primary infertility, but increases to 80% in men with secondary infertility, suggesting a progressive decline in male fertility.[9,15] A recent European meta-analysis showed that there is an adverse effect of varicoceles on semen quality among men unselected for fertility status. Nevertheless, data in a Chinese population are lacking.
Therefore, the aim of the present study was to examine the prevalence of varicoceles among Chinese men with infertility and to examine the factors associated with semen quality. The findings of this study provided clear data on the risk factors for poor seminal fluid quality in Chinese males, which could help identify the risk factors that could be modulated to improve semen quality.
2.1 Study design and patients
This was a cross-sectional study of male patients treated for infertility at the Reproductive Medicine Department of the Affiliated Hospital of Guangdong Medical University from October 2012 to December 2015. A total of 8648 patients were initially screened. The inclusion criteria were duration of infertility ≥ 1 year; abstinence of 2 to 7 days; and no fertility drugs in the past 6 months. The exclusion criteria were azoospermia; or incomplete outpatient data. A total of 8648 patients were screened and 5447 were included.
This study was approved by the Reproductive Ethics Committee of the Affiliated Hospital of Guangdong Medical University. All subjects signed the informed consent forms.
2.2 Data collection
A detailed medical history inquiry and physical examination were performed. Semen analysis and microbiological culture of semen were examined. Demographic information and physical examination results of the patients were collected. The patients were divided into 2 groups based on the presence of varicoceles. Occupational hazards were evaluated and classified into 4 groups: high temperature and heat exposure (e.g., cooks and drivers); toxic substance exposure (e.g., building and decoration workers, crews, farmers, hairdressing workers, factory workers, and petroleum workers); computer radiations (e.g., designers and civil service staffs); and no obvious risk factor (e.g., teachers, medical personnel, business personnel, breed personnel, self-employed businessmen, soldiers, and policemen). Abnormal epididymis referred to enlargement of the head or tail of the epididymis.
2.3 Semen collection
The semen was collected after an abstinence of 2 to 7 days. Urine was collected, and the hands and penises were washed using soap. After rinsed off the soap, the hands and penises were dried using new disposable towels. Semen was collected by masturbation and injected into a sterile container. Aseptic incubation was immediately performed for 100 μL of semen in Mycoplasma urealytium and nonspecific bacterial culture. Remaining semen in the container was used to perform semen analysis after liquefaction.
2.4 Seminal parameters
Examinations of the amount of semen and sperm morphology were performed according to seminal parameter detection methods recommended by the World Health Organization. Concentration of sperms (106/mL) and forward sperm motility (%) were measured using a sperm class analyzer (SCA) (Microptic S.L., Barcelona, Spain). Sperm morphology was examined using Papanicolaou staining. Optimized semen (10 μL) was dropped at one end of a slide glass, and the pull-thin technology was used to coat semen on the surface of the slide. After air drying, staining was performed using Papanicolaou staining. Using oil microscopy, 200 sperms were examined repeatedly and the percentage of normal sperm morphology of each semen sample was calculated. The morphological assessment of the sperm was performed strictly according to the WHO Laboratory Manual for the Examination and Processing of Human Semen (5th edition)  and 200 sperms were assessed. The parameters of the sperms were determined after 2 examinations.
Sperms included head, neck, connecting piece, tail, and end piece. It is difficult to observe the end piece of sperms through an optical microscope, so it was considered that sperm was constituted by head (and neck) and tail (connecting piece and tail). Only the sperms with normal head and tail were called normal, and all the other sperms were called abnormal. More specifically, according to the classification criteria of abnormal sperm described by the World Health Organization, the abnormalities include head abnormality, including big head, small head, conical head, pear-shaped head, round head, amorphous head, head with vacuole (with 2 or more vacuoles, or the size of unstained vacuole was larger than 20% of the area of the head), vacuole at the postacrosomal region, too big or small acrosome (less than 40% of the head area, or larger than 70% of the head area), 2 heads, or any combination of these abnormalities; neck and middle part abnormality, including asymmetric connecting of the middle part to the head, too thick or irregular, acute-angle bending, abnormally thin middle part, or any combination of these abnormalities; tail abnormality, including short tail, multiple tails, broken tail, hairpin-shaped smooth bending, acute angle bending, irregular thickness, curling, or any combination of these abnormalities; or excessive residual cytoplasm, which is mainly found in sperms from abnormal spermatogenesis; the features of such sperms include containing large volume of irregular stained cytoplasm, of which the volume is over one-third of the head area; defects in the middle part are also very common.
2.5 Statistical analysis
Continuous data were checked using the Kolmogorov–Smirnov test to see if they met the normal distribution. Normally distributed data were presented as mean ± standard deviation (SD) and analyzed with the Student t test. Non-normally distributed data were presented as median (range) and analyzed using the Mann–Whitney U test. Categorical data were presented using frequencies and analyzed with the Chi-square test or the Fisher exact test, as appropriate. Multiple linear regression analyses were used to examine the factors independently associated with the seminal parameters (dependent variables). Results were presented using the B value (the coefficient of the model) and the 95% confidence interval (95% CI) for the B value. Statistical analysis was performed using SPSS 22.0 (IBM, Armonk, NY). Two-sided P < .05 were considered to be statistically significant.
3.1 Characteristics of the patients
Table 1 presents the characteristics of the patients. Patients with varicoceles were slightly younger (P = .046), had smaller testis (P = .019), had a higher frequency of abnormal epididymis (P < .001), had a slightly shorter infertility duration (P = .046), and had a lower frequency of smokers (P = .012). There was no difference in the distribution of the occupations (P = .777).
3.2 Seminal parameters
Table 2 presents the seminal parameters. The varicocele group showed larger semen volume (P = .01), lower sperm concentration (P < .001), lower total sperm count (P < .001), lower proportion of spermatozoa with normal morphology (P < .001), lower total count of normal spermatozoa (P < .001), and lower proportion of motile spermatozoa (P < .001).
3.3 Multiple linear regression analyses
Table 3 presents the multiple linear regression analyses of factors associated with the seminal parameters. Each semen quality parameter was tested separately with the potential risk factors. Age was independently associated with semen volume (B = −0.023, 95% CI: −0.031 to −0.016, P < .001), semen concentration (B = 0.486, 95% CI: 0.277–0.695, P < .001), proportion of sperms with normal morphology (B = −0.030, 95% CI: −0.059 to −0.002, P = .033), motility (B = −0.437, 95% CI: −0.537 to −0.338, P < .001), and forward movement sperm count (B = −1.064, 95% CI: −1.561 to −0.566, P < .001).
Primary/secondary infertility was associated with semen volume (B = 0.177, 95% CI: 0.089–0.264, P < .001), proportion of sperms with normal morphology (B = 0.411, 95% CI: 0.098–0.752, P = .010), motility (B = 2.323, 95% CI: 1.211–3.434, P < .001), total sperm count (B = 17.223, 95% CI: 8.903–25.543, P < .001), and forward movement sperm count (B = 9.488, 95% CI: 3.971–15.005, P = .001).
Occupation was independently associated with sperm concentration (B = −3.478, 95% CI: −5.704 to −1.252, P = .002), total sperm count (B = −10.537, 95% CI: −18.748 to −2.326, P = .012), and forward movement sperm count (B = −7.026, 95% CI: −12.202 to −1.849, P = .008).
Cigarette smoking was independently associated with semen volume (B = −0.090, 95% CI: −0.171 to −0.009, P = .029), sperm concentration (B = −3.294, 95% CI: −5.500 to −1.088, P = .003), motility (B = 1.384, 95% CI: 0.355–2.413, P = .008), and total sperm count (B = −13.495, 95% CI: −21.597 to −5.394, P = .001).
Vas deferens status was independently associated with sperm volume (B = 0.623, 95% CI: 0.092–1.153, P = .033).
Epididymis status was independently associated with sperm concentration (B = −3.996, 95% CI: −6.418 to −1.574, P = .001), total sperm count (B = −12.804, 95% CI: −21.676 to −3.932, P = .005), and forward movement sperm count (B = −6.579, 95% CI: −12.201 to −0.956, P = .022).
Testis size was independently associated with semen volume (B = 0.085, 95% CI: 0.018–0.153, P = .013), sperm concentration (B = 16.580, 95% CI: 14.749–18.410, P < .001), proportion of sperms with normal morphology (B = 0.953, 95% CI: 0.704–1.202, P < .001), motility (B = 4.985, 95% CI: 4.105–5.866, P = .008), total sperm count (B = 58.807, 95% CI: 52.062–65.553, P < .001), and forward movement sperm count (B = 30.686, 95% CI: 26.322–35.051, P < .001).
Finally, varicoceles were independently associated with semen volume (B = −0.153, 95% CI: −0.245 to −0.062, P = .001), sperm concentration (B = 9.633, 95% CI: 7.152–12.114, P < .001), proportion of sperms with normal morphology (B = 0.951, 95% CI: 0.623–1.278, P < .001), motility (B = 3.835, 95% CI: 2.675–4.995, P < .001), total sperm count (B = 22.481, 95% CI: 13.333–31.629, P < .001), and forward movement sperm count (B = 15.553, 95% CI: 9.777–21.329, P < .001).
The association of varicoceles with infertility is well established,[6,8,9] but the exact effect of varicoceles on semen quality among patients with infertility is still unclear. Therefore, the objective of this study was to examine the prevalence of varicoceles among Chinese men with infertility and to examine the factors associated with semen quality. Results showed that varicoceles were present in 26% of Chinese male patients with infertility. Varicoceles were independently associated with sperm concentration, proportion of sperms with normal morphology, motility, total sperm count, and forward movement sperm count. The results of the present study provide insightful data about the risk factors for poor semen quality in Chinese male with infertility.
Varicocele are present in 35% to 40% of men with primary infertility, and in 80% of men with secondary infertility.[9,15] A recent study showed that varicoceles were associated with impaired testicular function as shown by lower sperm parameters and decreased testosterone levels. In addition, increasing grade of varicocele seems to be associated with worst sperm parameters. Supporting the association between varicoceles and infertility, surgical repair of varicoceles has been shown to increase sperm concentration and to improve sperm motility.[20–24] A recent meta-analysis showed that varicocele repair improves sperm parameters, probably by reducing sperm oxidative stress and DNA damage. All types of repair improve these parameters, but microsurgical repair seems to produce the best outcomes. In the present study, the multiple linear regression analyses performed with a large number of patients showed that the presence of varicocele was an independent predictor of poorer sperm parameters (i.e., smaller sperm volume, lower sperm concentration, abnormal sperm morphology, lower motility, lower total sperm count, and lower forward movement sperm count) among infertile Chinese men.
The association between age and sperm parameters is controversial. In a general manner, a study showed a decline in the likelihood of pregnancy, independent from the women's age, and increasing with age. On the contrary, age does not seem to affect semen volume, sperm count, and sperm motility in men consulting infertility clinics, but a review of the literature suggests that increasing age is associated with lower semen volume, sperm motility, and sperm morphology, but not with sperm concentration. A study showed that younger age was associated with better improvements in total motile sperm counts after microsurgical varicocele repair compared with older men. In the present study, age was independently associated with semen volume, motility, and total sperm count. Discrepancies among the present study and previous ones[25–27] could be due to a number of factors, including population, genetics, stress, and diet. Additional studies are necessary to examine these factors.
Varicoceles may lead to elevated scrotal temperature, which impairs spermatogenesis. Among occupational hazards, working at high temperatures may also contribute to increased scrotal temperature, contributing to infertility.[28,29] Exposure to toxic substances such as solvents and heavy metals has been reported to impair spermatogenesis.[30,31] Accordingly, in the present study, even if occupations were similar between patients with and without varicoceles, occupations were independently associated with sperm concentration, motility, total sperm count, and forward movement sperm count.
The present study is not without limitations. Albeit the sample size was large, it was from a single center. In addition, because of the retrospective nature of the study, many interesting data (such as hormone levels) could not be included in the analyses. The occupational risk factors were examined on the basis of the occupation of each patient, but we could not rule out other types of environmental exposures (e.g., at home or during recreational activities). The oxidative stress profile of the patients was not assessed. Finally, the effect of varicocele repair was not assessed because of the cross-sectional design of the study. We investigated the effects of varicocele on the quality of semen in the male partner of infertile couples. The spouse also underwent corresponding examinations, but this does not mean that all spouses were healthy and fertile, which introduce a bias. Additional studies are still necessary to determine adequately the contribution of varicoceles and other factors on semen quality among infertile men.
In conclusion, varicoceles were present in 26% of Chinese male patients with infertility. Varicoceles were independently associated with sperm volume, sperm concentration, proportion of sperms with normal morphology, motility, total sperm count, and forward movement sperm count. The present study suggests that the presence of varicoceles could explain many cases of male infertility, but that other factors such as age and occupational risks have to be taken into account. Nevertheless, many issues remain unanswered and additional studies will have to examine the molecular risk factors (such as oxidative stress) associated with male infertility.
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