Risk factors associated with sperm DNA fragmentation

Risk factors associated with sperm DNA fragmentation

Ashok Agarwal1, Chak-Lam Cho2, Ahmad Majzoub3, Sandro C. Esteves4

1American Center for Reproductive Medicine, Cleveland Clinic, Cleveland, OH, USA; 2Division of Urology, Department of Surgery, Kwong Wah Hospital, Hong Kong, China; 3Department of Urology, Hamad Medical Corporation, Doha, Qatar; 4ANDROFERT, Andrology and Human Reproduction Clinic, Referral Center for Male Reproduction, Campinas, SP, Brazil

Correspondence to: Ashok Agarwal. Professor and Director, American Center for Reproductive Medicine, Cleveland Clinic, Mail Code X-11, 10681 Carnegie Avenue, Cleveland, OH 44195, USA. Email: AGARWAA@ccf.org.

Response to: Franco JG Jr. Sperm DNA fragmentation. Transl Androl Urol 2017;6:S516-8.

Submitted Apr 11, 2017. Accepted for publication Apr 11, 2017.

doi: 10.21037/tau.2017.04.18

Dr. Franco (1) in his commentary in response to the practice recommendations by Agarwal et al. (2) provides information on several important aspects of sperm DNA fragmentation (SDF), especially the impact of paternal age, overweight and varicocele; and finally the author concluded by listing the current limitations of SDF tests.

The association between advanced paternal age and increase in SDF and the implication to pregnancy outcomes is one of the topics of our discussion. Paternal age, in contrast to female age, has become less of a concern over the last few decades ever since the introduction of assisted reproduction. Intracytoplasmic sperm injection (ICSI) has bypassed, to a certain extent, the most severe forms of male infertility. However, the relationship between paternal age and pregnancy outcome is clear. Semen parameters begin a steady decline after the age of 35 (3). Significantly more SDF is reported in men after the age of 40 (4). Time-to-pregnancy (TTP), which is an excellent measure of fertility potential, increases with an increase in male age. The “Groningen Expert Center for Kids with Obesity (GECKO) Drenthe” study from the Netherlands reported that paternal age was highly correlated with TTP on multivariate regression analysis based on data from 1,924 couples. The hazard ratio of paternal age was 1.31, 1.11 and 0.91 for age <25, 25–30 and >35 years respectively when compared to the reference category of 30–35 years of age (5). Hassan et al. also reported an increase in TTP in men over the age of 45. Their partner’s relative risk of an increase in TTP over one and two years rose to 4.6 and 12.5 respectively (6). There were exponentially fewer infants born to fathers over 35 to 39 years of age and older compared to younger age groups. Data from the Spanish National Statistics Institute analyzing a total of 454,753 infants in year 2004 demonstrated a constant decline in male fecundity from 35 to 39 years of age at a rate of 21–23% per year up to 80 years of age (7). Dr. Franco raised another point suggesting a possible correlation between age-related SDF and mitochondrial damage which is logical. Age-associated increase in oxidative stress is the most widely accepted hypothesis that explains the association between male age and SDF (8). Oxidative stress exerts its negative effect on sperm by various mechanisms including damage to mitochondrial DNA (9). In fact, mitochondria may represent a possible source of reactive oxygen species in sperm (10). However, contrary to the author’s suggestion that spermatozoal apoptosis is not correlated with ageing, there is evidence to show that oxidative stress can induce apoptosis in mature spermatozoa (11) and allow production of abnormal spermatozoa (12). These findings suggest a possible relationship between advanced paternal age and apoptosis of sperm.

Male obesity has been linked to subfecundity and a dose-response relationship between increasing body mass index and subfecundity has been reported (13). The exact underlying mechanism is unknown and SDF has been proposed as a possible mediating factor from various studies (2). While weight reduction is associated with improvements in reproductive outcomes in female (14), the effect of such treatment on male subfertility and/or SDF is less clear. Few emerging studies revealed that weight loss in severely obese men leads to improved semen parameters and reproductive hormonal profile; however, no change in SDF measured by sperm chromatin structure assay (SCSA) was observed (15,16). Further studies are required to delineate the mechanism of obesity leading to male subfertility and the effect of weight reduction treatment.

Although larger well-designed studies are welcomed to better define the relationship between varicocele and SDF, the well-executed systematic review by Zini and Dohle provides the best evidence supporting such a relationship (17). The association is further supported by the finding that varicocele itself is associated with SDF even when fertility has not been compromised (17). The efficacy of varicocele repair in alleviating oxidative stress (18), increasing seminal antioxidants (19), and decreasing SDF (20-22) has been demonstrated. The role of antioxidants as a therapeutic alternative or adjuvant therapy in varicocele is not well established due to limited amount of data (23,24). Various sperm selection techniques have been reported to be effective in selecting spermatozoa with reduced levels of SDF (25,26), but their effect on clinical outcomes is yet to be confirmed. Current sperm selection techniques are limited by the fact that none of them could completely remove sperm with DNA damage or aneuploidies (27). Varicocelectomy, by correction of the underlying etiology, remains the only treatment option that possibly allows natural conception by restoring fertility potential. The procedure also offers the lowest risk of genetic defects to offsprings. Therefore, varicocelectomy should be the preferred treatment option in patients with varicocele and high SDF.

Lastly, we agree that current SDF testing has its own limitations. While waiting for development of new methodologies, standardization of current techniques in combination with good quality control will improve the performance of SDF tests. A recent study demonstrated that the utilization of a standardized protocol and identical bench top flow cytometry instrument for TUNEL assay offers a very high degree of accuracy between different laboratories (28). In fact, despite different SDF tests employed, the correlation between SDF and natural pregnancy/assisted reproductive technology/miscarriage has been demonstrated (29).




Conflicts of Interest: The authors have no conflicts of interest to declare.


  1. Franco JG Jr. Sperm DNA fragmentation. Transl Androl Urol 2017;6:S516-S518.
  2. Agarwal A, Majzoub A, Esteves SC, et al. Clinical utility of sperm DNA fragmentation testing: practice recommendations based on clinical scenarios. Transl Androl Urol 2016;5:935-50. [Crossref] [PubMed]
  3. Dunson DB, Baird DD, Colombo B. Increased infertility with age in men and women. Obstet Gynecol 2004;103:51-6. [Crossref] [PubMed]
  4. Varshini J, Srinag BS, Kalthur G, et al. Poor sperm quality and advancing age are associated with increased sperm DNA damage in infertile men. Andrologia 2012;44 Suppl 1:642-9. [Crossref] [PubMed]
  5. Mutsaerts MA, Groen H, Huiting HG, et al. The influence of maternal and paternal factors on time to pregnancy-a Dutch population-based birth-cohort study: the GECKO Drenthe study. Hum Reprod 2012;27:583-93. [Crossref] [PubMed]
  6. Hassan MA, Killick SR. Effect of male age on fertility: evidence for the decline in male fertility with increasing age. Fertil Steril 2003;79 Suppl 3:1520-7. [Crossref] [PubMed]
  7. Matorras R, Matorras F, Expósito A, et al. Decline in human fertility rates with male age: a consequence of a decrease in male fecundity with aging? Gynecol Obstet Invest 2011;71:229-35. [Crossref] [PubMed]
  8. Sharma R, Biedenharn KR, Fedor JM, et al. Lifestyle factors and reproductive health: taking control of your fertility. Reprod Biol Endocrinol 2013;11:66. [Crossref] [PubMed]
  9. Aitken RJ, Koppers AJ. Apoptosis and DNA damage in human spermatozoa. Asian J Androl 2011;13:36-42. [Crossref] [PubMed]
  10. Koppers AJ, De Iuliis GN, Finnie JM, et al. Significance of mitochondrial reactive oxygen species in the generation of oxidative stress in spermatozoa. J Clin Endocrinol Metab 2008;93:3199-207. [Crossref] [PubMed]
  11. Agarwal A, Sekhon LH. Oxidative stress and antioxidants for idiopathic oligoasthenoteratospermia: Is it justified? Indian J Urol 2011;27:74-85. [Crossref] [PubMed]
  12. Sinha Hikim AP, Swerdloff RS. Hormonal and genetic control of germ cell apoptosis in the testis. Rev Reprod 1999;4:38-47. [Crossref] [PubMed]
  13. Ramlau-Hansen CH, Thulstrup AM, Nohr EA, et al. Subfecundity in overweight and obese couples. Hum Reprod 2007;22:1634-37. [Crossref] [PubMed]
  14. Zain MM, Norman RJ. Impact of obesity on female fertility and fertility treatment. Womens Health (Lond) 2008;4:183-94. [Crossref] [PubMed]
  15. Håkonsen LB, Thulstrup AM, Aggerholm AS, et al. Does weight loss improve semen quality and reproductive hormones? Results from a cohort of severely obese men. Reprod Health 2011;8:24. [Crossref] [PubMed]
  16. El Bardisi H, Majzoub A, Arafa M, et al. Effect of bariatric surgery on semen parameters and sex hormone concentrations: a prospective study. Reprod Biomed Online 2016;33:606-11. [Crossref] [PubMed]
  17. Zini A, Dohle G. Are varicoceles associated with increased deoxyribonucleic acid fragmentation? Fertil Steril 2011;96:1283-7. [Crossref] [PubMed]
  18. Sakamoto Y, Ishikawa T, Kondo Y, et al. The assessment of oxidative stress in infertile patients with varicocele. BJU Int 2008;101:1547-52. [Crossref] [PubMed]
  19. Hamada A, Esteves SC, Agarwal A. Insight into oxidative stress in varicocele-associated male infertility: part 2. Nat Rev Urol 2013;10:26-37. [Crossref] [PubMed]
  20. Zini A, Azhar R, Baazeem A, et al. Effect of microsurgical varicocelectomy on human sperm chromatin and DNA integrity: a prospective trial. Int J Androl 2011;34:14-9. [Crossref] [PubMed]
  21. Li F, Yamaguchi K, Okada K, et al. Significant improvement of sperm DNA quality after microsurgical repair of varicocele. Syst Biol Reprod Med 2012;58:274-7. [Crossref] [PubMed]
  22. Wang YJ, Zhang RQ, Lin YJ, et al. Relationship between varicocele and sperm DNA damage and the effect of varicocele repair: a meta-analysis. Reprod Biomed Online 2012;25:307-14. [Crossref] [PubMed]
  23. Cavallini G, Biagiotti G, Ferraretti AP, et al. Medical therapy of oligoasthenospermia associated with left varicocele. BJU Int 2003;91:513-8. [Crossref] [PubMed]
  24. Paradiso Galatioto G, Gravina GL, Angelozzi G, et al. May antioxidant therapy improve sperm parameters of men with persistent oligospermia after retrograde embolization for varicocele? World J Urol 2008;26:97-102. [Crossref] [PubMed]
  25. Gosálvez J, Migueles B, López-Fernández C, et al. Single sperm selection and DNA fragmentation analysis: The case of MSOME/IMSI. Nat Sci 2013;5:7-14.
  26. Garolla A, Cosci I, Menegazzo M, et al. Sperm selected by both birefringence and motile sperm organelle morphology examination have reduced deoxyribonucleic acid fragmentation. Fertil Steril 2014;101:647-52. [Crossref] [PubMed]
  27. Celik-Ozenci C, Jakab A, Kovacs T, et al. Sperm selection for ICSI: shape properties do not predict the absence or presence of numerical chromosomal aberrations. Hum Reprod 2004;19:2052-9. [Crossref] [PubMed]
  28. Ribeiro S, Sharma R, Gupta S, et al. Inter- and intra-laboratory standardization of TUNEL assay for assessment of sperm DNA fragmentation. Andrology 2017;5:477-85. [Crossref] [PubMed]
  29. Agarwal A, Cho CL, Esteves SC. Should we evaluate and treat sperm DNA fragmentation? Curr Opin Obstet Gynecol 2016;28:164-71. [Crossref] [PubMed]
Cite this article as: Agarwal A, Cho CL, Majzoub A, Esteves SC. Risk factors associated with sperm DNA fragmentation. Transl Androl Urol 2017;6(Suppl 4):S519-S521. doi: 10.21037/tau.2017.04.18