Key Laboratory of Environment and Health, Ministry of Education & Ministry of Environmental Protection, and State Key Laboratory of Environmental Health (Incubating), Department of Occupational and Environmental Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
Reproductive Medical Center, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, Hubei, China.
Hum Reprod. 2019 Jan 1;34(1):155-162. doi: 10.1093/humrep/dey328.
What is the relationship between abnormal BMI and semen quality?
Underweight was significantly associated with lower sperm concentration, total sperm number and total motile sperm count, while overweight was significantly associated with lower semen volume, total sperm number and total motile sperm count.
Abnormal BMI has been associated with lower semen quality, but the results remain somewhat controversial. In addition, most previous studies have focused on the influence of obesity or overweight on semen quality, and evidence on the association between underweight and semen quality is rare.
STUDY DESIGN, SIZE, DURATION: This research was an observational study investigating 3966 sperm donors from a large sperm bank in Wuhan city, China. These donors passed the screening for sperm donation and underwent 29 949 semen examinations between 1 January 2013 and 9 April 2018.
PARTICIPANTS/MATERIALS, SETTING, METHODS: BMI was categorized into four groups: underweight (<18.5 kg/m2), normal weight (18.5-24.9 kg/m2), overweight (25-29.9 kg/m2) and obese (≥30 kg/m2). Semen volume, sperm concentration, total sperm number, total motility, progressive motility and total motile sperm count were determined by trained clinical technicians. Linear mixed models were used to conduct dose-response analyses between BMI and semen quality parameters.
Underweight was significantly associated with a 3.0% (95% CI: 0.1%, 5.8%), 6.7% (1.9%, 11.3%) and 7.4% (2.2%, 12.4%) reduction in sperm concentration, total sperm number and total motile sperm count, respectively. Overweight was significantly associated with a 4.2% (1.6%, 6.8%), 3.9% (0.9%, 6.9%) and 3.6% (0.2%, 6.9%) reduction in semen volume, total sperm number and total motile sperm count, respectively. Non-linear models including continuous BMI as a natural cubic spline function yielded similar results.
LIMITATIONS, REASONS FOR CAUTION: Our study subjects were sperm donors who are typically young and healthy, and therefore not representative of the general male population. Caution should be paid in generalizing our results to other populations. Furthermore, we did not measure the donors' weight repeatedly along with each semen donation; instead, we only measured it once during the screening, which may cause bias due to the variations of weight across time.
Our study provides evidence that underweight and overweight are associated with lower semen quality, and highlights the importance of maintaining a normal weight for men.
STUDY FUNDING/COMPETING INTEREST(S): This work was supported by the Health and Family Planning Commission of Hubei Province (Grant number WJ2015MA027), the Hubei Provincial Committee of the Communist Youth League of China, and Center for Global and Regional Environmental Research at the University of Iowa. The authors declare that there are no conflicts of interest.
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BMI 异常与精液质量之间存在什么关系？
体重过轻与精子浓度、总精子数和总活力精子计数降低显著相关，而超重与精液量、总精子数和总活力精子计数降低显著相关。
BMI 异常与精液质量降低有关，但结果仍存在一定争议。此外，大多数先前的研究都集中在肥胖或超重对精液质量的影响上，而关于体重过轻与精液质量之间关联的证据很少。
研究设计、大小和持续时间：这是一项观察性研究，调查了来自中国武汉市一家大型精子库的 3966 名精子捐赠者。这些捐赠者通过了精子捐赠筛选，并在 2013 年 1 月 1 日至 2018 年 4 月 9 日期间接受了 29949 次精液检查。
参与者/材料、设置、方法：BMI 分为四组：体重过轻（<18.5kg/m2）、正常体重（18.5-24.9kg/m2）、超重（25-29.9kg/m2）和肥胖（≥30kg/m2）。精液量、精子浓度、总精子数、总活力、前向运动和总活力精子计数由经过培训的临床技术人员确定。线性混合模型用于BMI与精液质量参数之间的剂量-反应分析。
体重过轻与精子浓度、总精子数和总活力精子计数分别降低 3.0%（95%CI：0.1%，5.8%）、6.7%（1.9%，11.3%）和 7.4%（2.2%，12.4%）显著相关。超重与精液量、总精子数和总活力精子计数分别降低 4.2%（1.6%，6.8%）、3.9%（0.9%，6.9%）和 3.6%（0.2%，6.9%）显著相关。包括 BMI 作为自然三次样条函数的非线性模型得出了类似的结果。
局限性、谨慎原因：我们的研究对象是精子捐赠者，他们通常年轻且健康，因此不能代表一般男性人群。在将我们的结果推广到其他人群时应谨慎。此外，我们没有在每次精液捐赠时反复测量捐赠者的体重；相反，我们只在筛选期间进行了一次测量，由于体重随时间的变化，这可能会导致偏差。
我们的研究提供了体重过轻和超重与精液质量降低相关的证据，并强调了男性保持正常体重的重要性。
研究资金/利益冲突：这项工作得到了湖北省卫生和计划生育委员会（资助号 WJ2015MA027）、湖北省共青团和爱荷华大学全球和区域环境研究中心的支持。作者声明不存在利益冲突。
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