Human Factors Affecting Recovery of Sperm Motility After Cryopreservation: A Retrospective Analysis

BackgroundAlthough studies have suggested that sperm motility may influence assisted reproductive technology outcomes, current studies on factors affecting post-cryopreservation motility recovery are largely limited to evaluating cryopreservation techniques.ObjectiveTo evaluate human factors associated with the recovery of sperm motility after cryopreservation.DesignWe retrospectively reviewed patients undergoing sperm cryopreservation at a single institution between September 2021 and January 2024.MethodsPre- and post-thaw motility, demographics, clinical history, and pre-retrieval laboratory values were collected. The primary outcome was percent motility recovery, defined as post-thaw motility divided by pre-freeze motility multiplied by 100. Multivariable linear regression was adjusted for baseline motility, age, BMI category, smoking status, alcohol use, race, chemotherapy exposure, and radiation exposure. A secondary model used absolute post-thaw motility to assess ratio-based ceiling effects.ResultsAmong 184 patients, mean age was 30.4 (SD 9.07) and mean BMI was 25.9 (SD 4.87). Mean pre- and post-freezing sperm motility and percent recovery were 45.5% (SD 22.1), 23.7% (SD 13.8), and 53.9% (SD 24.5), respectively. Increasing age was associated with lower motility recovery (β=-0.525, p=0.015) and post-thaw motility (β=-0.178, p=0.025). Higher pre-freeze motility was inversely associated with percent recovery (β=-0.201, p=0.016), but positively associated with post-thaw (β=0.478, p<2*10^-16).ConclusionsAdvancing age was associated with lower proportional motility recovery and lower absolute post-thaw motility. The inverse association between baseline motility and percentage recovery likely reflects ratio-based mathematical constraints, not worse absolute post-thaw motility. Older patients may benefit from earlier or multiple cryopreservations to maximize motile sperm availability.