The Impact of High Ambient Temperature on Human Sperm Parameters: A Meta-Analysis

BACKGROUND: Global warming, lifestyle, or working in a high temperature environment leads to have increased health risk factors. This meta-analysis was conducted to determine the impact of high ambient temperature on male reproductive function. METHODS: Scientific articles were screened in the database including MEDLINE, EMBASE, National center for biotechnology information (NCBI) or Web of Science with relating keywords. Impact data of high ambient temperature on semen parameters were extracted and analyzed by STATA software according to the Random Effects Model. The high ambient temperature exposure group and Non-exposure group were compared using the standard mean difference (SMD). Publications were evaluated for publication bias by Egger test. RESULTS: Nine articles were finally selected from databases examining the effect of high ambient temperature on male reproductive health of 356 men from Iran, Italy, Thailand, China, Egypt. High ambient temperature showed a significant decrease in the seminal parameters, semen volume during each ejaculation (SMD = −0.74; 95% CI −1.11, −0.36), sperm concentration (SMD = −1.07; 95% CI −1.42, −0.72), total sperm count (SMD = −1.52; 95% CI −2.96, −0.08), sperm motility (SMD = −1.93; 95% CI −2.83, −1.04), sperm progressive motility (SMD = −1.65; 95% CI −2.39, −0.91) and normal morphology (SMD = −2.41; 95% CI −3.30, −1.52). CONCLUSION: High ambient temperature negatively affects sperm quality, including decreased semen volume, sperm count, sperm concentration, motility and normal morphology. This might lead to protective strategies to avoid the adverse effects of high ambient temperature on male fertility.