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The Relationship between Age, Ejaculatory Frequency, Waiting Time to Post-Vasectomy Semen Analysis, and Clearance Rate
Scott Daniel Matson, MD1, Sonam Saxena, BS
2, Daniel Nolte, MS
3, Stacey A. Kenfield, ScD
4, Julie Gonzales, HS
3, David Shin, MD
2, James F. Smith, MD
4.
1St. Francis Hospital and Medical Center, Hartford, CT, USA,
2Hackensack University Medical Center, Hackensack, NJ, USA,
3Fellow Health, San Leandro, CA, USA,
4Dept of Urology, UCSF, San Francisco, CA, USA.
Background: The effects of age, waiting time and ejaculatory frequency on vasectomy clearance have not been well studied.
Methods: This IRB-approved, prospective cohort study followed men (n=79,826) in the USA who had a vasectomy between April 2021 and February 2025 and had subsequent testing with the Fellow Health post-vasectomy semen analysis (PVSA) system. The relationship between age, number of post-vasectomy ejaculations (PVE), waiting time (WT, weeks) from vasectomy and PVSA outcome (i.e. azoospermia “clearance”) was analyzed at first PVSA. A multivariable logistic regression model was constructed to assess the independent effects of these variables and the probability of clearance.
Results: Across age groups, clearance declined with age (18-29: 94%, 30-34: 91%, 35-39: 89%, 40-44: 86%, 45-49: 82%, 50+: 77%, p < 0.001). WT was associated with clearance (<8: 79%, 8-12: 86%, 13-16: 88%, >16: 90%, Figure 2). Compared to men under 30, multivariable logistic regression demonstrated a reduced odds of clearance for older men (30-34: OR 0.7, 0.5-0.9; 35-39: OR 0.5, 0.4-0.7; 40-44: OR 0.3, 0.2-0.5; 45-49: OR 0.3, 0.2-0.4; 50+: OR 0.2, 0.1-0.3) even after adjusting for PVE and WT. Men who reported at least 10 PVE had a higher odds of clearance (OR 2.3, 1.7-3.1) than those with 9 or fewer.
Conlusion: Older age is negatively correlated with PVSA clearance even after adjustment for ejaculation frequency and WT. The effect is most notable in men older than 50, where 23% have a non-azoospermia result. Greater than 10 PVE is correlated with improved vasectomy clearance.
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