Many risk factors can potentially influence sperm quality. Telomeres confer stability to the chromosome, and their dysfunction has been implicated in conditions such as cancer, ageing, and lifestyle. The impact of lifestyle on sperm telomeres is unclear. The objectives of this study were to assess the impact of lifestyle behaviours on sperm telomere length and to follow the correlation with pregnancy outcomes in patients undergoing in vitro fertilization (IVF). In this prospective observational study, sperm telomere length (TL) was analyzed.
The men were asked to report lifestyle behaviours including occupation (physical or sedentary), duration and amount of smoking, physical activity, dietary habits, and where they keep their cell phone (purse, pants, or shirt pocket). Correlations between semen analysis, TL, men’s habits and embryo quality and pregnancy outcomes were evaluated. Among the 34 recruited patients, 12 had longer TL and 13 had shorter TL. Sperm motility was negatively correlated with LT (Pearson’s correlation = −0.588, p = 0.002). Smoking negatively affected native sperm motility (53% motility in nonsmokers vs. 37% in smokers; p = 0.006).
However, there was no significant impact on TL. The group with longer telomeres showed a significant association with a healthy diet (10/12 vs 6/13; p = 0.05) and a tendency towards more weekly sports activity (16/84 vs 7/91; p = 0. 04) compared to the group with shorter telomeres. This study suggests that lifestyle, healthy diet, and sports activity are associated with long telomeres in sperm. Sperm quality is also influenced by the habits of patients. The study strongly recommends maintaining a healthy lifestyle to preserve general health and fertility.
Materials and methods
This prospective, non-interventional cohort study was conducted in the hospital’s IVF unit from November 2019 to November 2020.
Men who underwent IVF with or without intracytoplasmic sperm injection (ICSI), aged between 18 and 60, were eligible to participate in the study. On the day of oocyte collection (OPU), just after the couple provided the sperm for fertilization in the laboratory, written consent was obtained to use the remaining sperm for further evaluation. Those who agreed to participate were asked to answer the following questions about their lifestyle: occupation (physical or sedentary), time and amount of smoking, whether they practice regular physical activity, type of diet (Mediterranean, fast food, mainly intake of carbohydrates), and where they keep their cell phone (purse, pants pocket, shirt pocket, etc.) to examine the proximity of the cell phone to their genitals.
Semen was analyzed according to the World Health Organization criteria (volume ≥1.5 mL, concentration ≥15 × 106/mL, progressive motility ≥32%, and normal morphology ≥4%). These are accepted normal values (Cooper et al., 2010). Patients with severe oligo-terato-asthenospermia were excluded from the study.
- Embryo classification
IVF or ICSI was performed after oocyte retrieval. Mature oocytes were placed on EmbryoSlides and incubated in EmbryoScopeTM (Unisense FertiliTech, Aarhus, Denmark) for 3 to 5 days at 37°C in 5.8% CO2 and 5% O2 if ICSI was performed. Images of the embryos were captured every 10 minutes in seven focal planes, from the moment of the extraction of the second polar body and up to 120 hours after fertilization, to determine the exact moment of cell division. Embryos were classified according to the Known Implantation Data (KID) score, Alpha ESHRE score, and morphology.
All available embryos were assessed for quality based on cell count, symmetry, granularity, type, fragmentation percentage, multinucleated blastomere, and degree of compaction. A top-quality embryo was classified as one with 4 to 5 cells on day 2 or >6 blastomeres of the same size on day 3, ≤20% fragmentation, and no multinucleated cells. To avoid inter-observer errors, all measurements were performed by the same embryologist. No more than two embryos were transferred on day 3 or 5 of embryonic development; the remaining top-quality embryos were vitrified and used for the subsequent transfer of frozen embryos, in case pregnancy was not achieved.
- Determination of pregnancy
Fourteen days after the embryo transfer, the beta-hCG level was assessed. Clinical pregnancy was confirmed when a gestational sac with a fetal heartbeat was detected by ultrasound at 7 weeks of gestation.
- Sperm isolation and DNA extraction
Residual semen samples obtained on the day of the OPU were immediately transferred to the laboratory for further evaluation. The semen samples were allowed to liquefy for 30 min at 37°C. Total semen was centrifuged at 3400 rpm for 5 min to remove the supernatant. Pellets were resuspended and washed twice with 1000 µL of sterile phosphate-buffered saline (PBS, 0.5 M) at 3400 rpm for 5 min to remove cellular and non-cellular components before adding lysis buffer.
DNA from semen was extracted with the DNeasy Blood & Tissue kit (QIAGEN, Ontario, Canada) according to the manufacturer’s instructions. DNA concentration was measured using a NanoDrop spectrophotometer (Thermo Scientific). DNA samples were stored at -20°C until further analysis.
- Statistic analysis
Data normality was tested using the Kolmogorov-Smirnov and Shapiro-Wilk tests. The parametric variables that followed a normal distribution were analyzed using parametric tests; otherwise, nonparametric tests were applied. Descriptive statistics were applied, mainly mean ± standard deviation (SD), 95% confidence interval (CI), median, and interquartile range (IQR), as appropriate. As this study was the first to assess the impact of lifestyle on sperm LT, a pilot study was conducted on 34 patients.