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Background: Several studies indicate adverse effects of selected heat exposures on semen quality, but few studies have directly evaluated fertility as an endpoint. Objective: We evaluated prospectively the association between male heat exposures and fecundability, the per‐cycle probability of conception. Materials and methods: We analyzed data from 3041 couples residing in the United States or Canada who enrolled in a prospective preconception cohort study (2013–2021). At enrollment, males reported on several heat‐related exposures, such as use of saunas, hot baths, seat heaters, and tight‐fitting underwear. Pregnancy status was updated on female follow‐up questionnaires every 8 weeks until conception or a censoring event (initiation of fertility treatment, cessation of pregnancy attempts, withdrawal, loss to follow‐up, or 12 cycles), whichever came first. We used proportional probabilities regression models to estimate fecundability ratios (FR) and 95% confidence intervals (CIs) for the association between heat exposures and fecundability, mutually adjusting for heat exposures and other potential confounders. Results: We observed small inverse associations for hot bath/tub use (≥3 vs. 0 times/month: FR = 0.87, 95% CI: 0.70–1.07) and fever in the 3 months before baseline (FR = 0.94, 95% CI: 0.79–1.12; one cycle of follow‐up: FR = 0.84, 95% CI: 0.64–1.11). Little association was found for sauna use, hours of laptop use on one's lap, seat heater use, time spent sitting, and use of tight‐fitting underwear. Based on a cumulative heat metric, FRs for 1, 2, 3, and ≥4 versus 0 heat exposures were 0.99 (95% CI: 0.87–1.12), 1.03 (95% CI: 0.89–1.19), 0.94 (95% CI: 0.74–1.19), and 0.77 (95% CI: 0.50–1.17), respectively. Associations were stronger among men aged ≥30 years (≥4 vs. 0 heat exposures: FR = 0.60, 95% CI: 0.34–1.04). Conclusion: Male use of hot tubs/baths and fever showed weak inverse associations with fecundability. Cumulative exposure to multiple heat sources was associated with a moderate reduction in fecundability, particularly among males aged ≥30 years. [ABSTRACT FROM AUTHOR]

Background We launched the Boston University Pregnancy Study Online ( PRESTO) to assess the feasibility of carrying out an Internet-based preconception cohort study in the US and Canada. Methods We recruited female participants age 21-45 and their male partners through Internet advertisements, word of mouth, and flyers. Female participants were randomised with 50% probability to receive a subscription to FertilityFriend.com ( FF), a web-based programme that collects real-time data on menstrual characteristics. We compared recruitment methods within PRESTO, assessed the cost-efficiency of PRESTO relative to its Danish counterpart ( Snart- Gravid), and validated retrospectively reported date of last menstrual period ( LMP) against the FF data. Results After 99 weeks of recruitment (2013-15), 2421 women enrolled; 1384 (57%) invited their male partners to participate, of whom 693 (50%) enrolled. Baseline characteristics were balanced across randomisation groups. Cohort retention was similar among those randomised vs. not randomised to FF (84% vs. 81%). At study enrolment, 56%, 22%, and 22% couples had been trying to conceive for <3, 3-5, and ≥6 months, respectively. The cost per subject enrolled was $146 (2013 US$), which was similar to our companion Danish study and half that of a traditional cohort study. Among FF users who conceived, >97% reported their LMP on the PRESTO questionnaire within 1 day of the LMP recorded via FF. Conclusions Use of the Internet as a method of recruitment and follow-up in a North American preconception cohort study was feasible and cost-effective. [ABSTRACT FROM AUTHOR]

Objective The US Army recruits new soldiers from an increasingly obese civilian population. The change in weight status at entry into the Army between 1989 and 2012 and the demographic characteristics associated with overweight/obesity at entry were examined. Methods 1,741,070 unique individuals with complete sex, age, and anthropometric information contributed data to linear and logistic regressions examining time trends and associations between demographic characteristics and overweight/obesity. Results The prevalence of overweight (body mass index 25-<30 kg/m2) generally increased, from 25.8% (1989) to 37.2% (2012), peaking at 37.9% (2011). The prevalence of obesity (body mass index ≥30 kg/m2) also increased from 5.6% (1989) to 8.0% (2012), peaking at 12.3% (2009); 2005-2009 annual prevalence exceeded 10%. The most consistent demographic characteristics predicting overweight/obesity were male sex, older age, Hispanic or Asian/Pacific Island race/ethnicity, and being married. There were no distinct geographic trends. Conclusions The US Army is not immune to the US obesity epidemic. Demographic characteristics associated with being overweight or obese should be considered when developing military-sponsored weight management programs for new soldiers. [ABSTRACT FROM AUTHOR]