Extended Abstract
Introduction
Infertility is a significant health concern with an increasing percentage with couples’ advanced age. Approximately 15% of couples experience infertility, with male factors contributing to 50% of cases. Over the past three decades, there has been a global trend toward delaying the age at which couples have their first child. This phenomenon is primarily attributed to socioeconomic factors, such as delayed marriage, increased life expectations, widespread use of contraceptions, and rising child-rearing costs in industrialized nations. In this context, male infertility has been linked to various sperm disorders stemming from hormonal and metabolic disturbances, stressful lifestyles, dietary factors, advancing paternal age, or other pathological conditions. These factors can collectively contribute to a decline in semen quality.
Obesity has been identified as an adversary of male fertility, with a high likelihood of compromising sperm quality. Spermatogenesis, the process of sperm production and differentiation, is recognized as a highly temperature-sensitive process in reproductive physiology, requiring an optimal temperature range of 32 to 35℃ for normal function in human testes. Excessive extratesticular heat production is considered a major issue among obese individuals, potentially stemming from increased scrotal adiposity and, occasionally, elevated suprapubic and thigh fat. Obesity can be associated with reduced testicular volume, alterations in spermatogenesis, and compromised quality of sperm parameters. Factors such as sedentary lifestyles, laptop use, saunas, and varicoceles can also contribute to elevated testicular temperature. In this context, excessive oxidative stress in obese individuals has been shown to play a pivotal role in the pathology of male infertility, potentially activating various inflammatory, immune, and apoptotic pathways. Oxidative stress levels increase with rising body mass index (BMI) due to heightened macrophage activation in semen. Moreover, increased BMI is significantly correlated with decreased sperm concentration and serum testosterone levels, along with elevated serum estradiol. A significant association has been reported between obesity and sperm DNA damage. Obese individuals with vitamin D deficiency exhibit reduced sperm motility and increased sperm DNA damage.
Extensive research has been conducted on the correlation of men’s age with spermatogenesis function and fertility potential so that a significant increase in severe sperm production disorders has been observed in older men with high BMIs compared to older men with normal BMIs. In studies, sperm DNA damage has been evaluated using the sperm chromatin structure assay (SCSA) in sperm samples, and this parameter has shown a significant correlation with men’s age, which could be linked to abnormal spermatogenesis function and increased oxidative stress. According to studies, increased sperm DNA damage and decreased quality of sperm parameters in older infertile men can negatively impact their treatment outcomes, particularly embryo quality, pregnancy, and even the health of future offspring.
Despite numerous studies demonstrating that increasing age and obesity in men can have a negative impact on sperm function, some studies have not observed this association, and some obese or older men have not experienced infertility and have fathered healthy children. The reason for this discrepancy may be correlated with small sample sizes in studies, differences in methods for evaluating sperm parameters or DNA and sperm chromatin tests, the study population, or other unknown factors. This study aimed to determine the correlation of sperm parameters with age and BMI in infertile men.
Methods
In this descriptive-analytical study, semen parameters (concentration, motility, and morphology), age, height, and weight of 7069 male participants were extracted from the medical records of infertile men referring to Isfahan Infertility and Fertility Center between February 2018 and August 2022.
Semen samples were collected in sterile containers through masturbation after 2 to 7 days of abstinence. After liquefaction, sperm parameters were examined and analyzed based on the World Health Organization (WHO) 2010 guidelines (WHO-2010).
Sample volume was determined by weighing the sample, sperm concentration was measured using a Neubauer hemacytometer, sperm morphology was assessed using the Diff-Quick staining method, and sperm motility was evaluated visually. Sperm count was calculated by multiplying the sample volume by the sperm concentration, and the percentage of progressive sperm motility was obtained by summing the percentages of rapid and slow progressive motility. Additionally, BMI was calculated by dividing the individual’s weight (kg) by the square of their height (m).
Results
A weak positive correlation was observed between men’s age and BMI. Additionally, semen volume, sperm concentration, and sperm count had a weak negative correlation with BMI. BMI showed a weak positive correlation with both progressive motility and the percentage of abnormal sperm morphology; however, no correlation was found between BMI and sperm motility. Semen volume, sperm motility, and progressive sperm motility had a weak inverse correlation with men’s age. No correlation was found between sperm count and men’s age. In an unexpected finding, with increasing age, sperm concentration exhibited a weak positive correlation, while the percentage of abnormal morphology exhibited a weak negative correlation.
Conclusion
Based on the results, as BMI increased in infertile men, semen volume, sperm concentration, and sperm count approximately decreased, while the percentage of abnormal morphology approximately increased. However, the observed correlation was weak. Therefore, obesity may influence the process of sperm production and differentiation, giving rise to a decrease in sperm count and an increase in the percentage of abnormal morphology.
Ethical Statement
This study was approved by the Research Ethics Committee of Royan Institute, Academic Center for Education, Culture and Research (ACECR) (IR.ACECR.ROYAN.REC.1401.031).
Funding
This research was supported by a grant (No. 401000022) from Royan Institute, ACECR.
Conflicts of Interest
No conflict of interest.
Acknowledgement
The authors would like to thank the officials and staff of Royan Institute of Animal Biotechnology and Isfahan Fertility and Infertility Center.
Key message: Increasing BMI and age in men may be associated with decreased sperm quality and fertility potential.