| Summary: | Infertility, defined as the inability to achieve clinical pregnancy after ≥12 months
of regular unprotected intercourse, is a growing problem in North America and the world.
Estimates place the percentage of couples experiencing infertility at around 15% in North
America. Currently, the U.S. health care costs for infertility treatment exceed $5.5 billion,
with these costs expected to increase as more couples use assisted reproductive
technologies (ART). Additionally, fertility issues are associated with psychological and
financial hardship for affected couples, and ART use has been associated with adverse
pregnancy outcomes.
One vital area of research that has been drastically understudied is male fertility.
Male factors are found to contribute to 30-50% of all infertility diagnoses, but the vast
majority of studies focus on women. This dissertation uses data from Pregnancy Study
Online (PRESTO), a preconception cohort study of pregnancy planners from North
America, to examine the role several male exposures have on fertility.
In the first study, we examined the association between a history of diagnosed
depression, current depressive symptoms, and psychotropic medication (PM) use with
fecundability. We found that a history of diagnosed depression, as well as currentvi
depressive symptoms, showed slight evidence of an association with decreased
fecundability, though this result was compatible with chance. Current psychotropic
medication (PM) and antidepressant use were associated with reduced fecundity,
particularly among those with current depressive symptoms. Current PM and selective
serotonin reuptake inhibitor (SSRI) use mediated part but not all of the relationship
between current depressive symptoms and fecundability.
In the second paper, we studied the role of testicular heat exposure in declining
fertility. We estimated the extent to which selected male heat exposures, including use of
saunas, hot tubs, and hot baths; use of restrictive underwear; time spent sitting; use of car
seat heaters; use of a laptop computer on one’s lap; and fever within the last 3 months
affected fecundability. Additionally, we attempted to create a composite heat score to
measure cumulative heat exposure. We found small inverse associations for sauna use,
hot tub/bath use, and seat heater use in the winter with fecundability. Additionally, we
found evidence of threshold for overall exposure to multiple heat factors.
The third paper focused specifically on occupational stress exposure, an
understudied source of exposure to stress. These occupational stressors included
employment status (employed or unemployed), number of hours worked, time of day
mainly worked, and a measure of job independence. We found that working non-daytime
shifts and being unemployed were associated with slightly decreased fecundability in
men. However, total hours worked per week and job independence score showed little
relation to reduced fecundability
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