![]() Chan School of Public Health and MGH.īetween 20, each man provided one semen sample and one blood sample on the same day. The study was approved by the Human Subject Committees of the Harvard T.H. ![]() All participants signed an informed consent form. Men between the ages of 18–56 years and without a history of vasectomy were eligible to participate in a study aimed at evaluating environmental determinants of fertility ( Meeker et al., 2011 Messerlian et al., 2018). Study participants were male partners of couples seeking infertility treatment at the Massachusetts General Hospital (MGH), Boston, MA, USA, between 20. To further address this question, we investigated whether men’s reported type of underwear most frequently worn is associated with semen parameters, markers of sperm DNA damage and circulating levels of reproductive hormones among men attending a fertility center. It is still unclear whether men’s choice of underwear is related to other markers of testicular function, such as serum reproductive hormone levels. Some epidemiological studies have investigated whether men who wear tighter underwear, a modifiable lifestyle factor strongly related to higher scrotal temperatures ( Brindley, 1982 Ahmad et al., 2012), have poorer semen quality, compared to men who wear looser underwear however, results have been inconsistent ( Parazzini et al., 1995 Munkelwitz and Gilbert, 1998 Jung et al., 2001 Povey et al., 2012 Jurewicz et al., 2014 Pacey et al., 2014 Sapra et al., 2016). However, it is still unclear which factor(s) is responsible for this decline. These negative trends may be the consequence of environmental and lifestyle factors that may directly contribute to diminished testicular function, such as increased exposure to endocrine disrupting chemicals ( Bergman et al., 2013 Hauser et al., 2015), higher prevalence of obesity ( Finucane et al., 2011 Sermondade et al., 2013), deteriorating diet quality ( Wong et al., 2000 USDA, 2017) and elevated scrotal temperatures ( Ahmad et al., 2012 Zhang et al., 2015), among others. Some have also reported a concomitant downward trend in testosterone levels among men ( Andersson et al., 2007 Travison et al., 2009 Nyante et al., 2012). Three meta-analyses ( Carlsen et al., 1992 Swan et al., 2000 Levine et al., 2017) and several single-center studies ( Auger et al., 1995 Jorgensen et al., 2001, 2011 Rolland et al., 2012 Mendiola et al., 2013) have reported a decrease in sperm counts in Western countries during both the 20th and 21st centuries.
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