Causes of Decreased Sperm Motility
Temperature-related factors are the most common cause of a significant decrease in sperm motility from normal (80%) to impaired (50%) levels, with higher storage temperatures causing more rapid motility decline. 1
Temperature Effects on Sperm Motility
- Storage temperature impact: Long-term storage at body temperature (37°C) results in reduced motility in a time-dependent manner, with more rapid and extensive decline compared to storage at room temperature 1
- Sperm motility decreases at both room and body temperature over time, but deteriorates faster at 37°C 1
- Higher storage temperatures (body/testis temperature) not only reduce motility but also overall sperm quality 1
- Centrifugation temperature can affect motility: One study found higher percentage of motile sperm after centrifugation at 34°C compared to room temperature 1
Energy Metabolism Factors
- Sperm motility depends on ATP production through two main pathways 2:
- Oxidative phosphorylation in the midpiece
- Glycolysis in the principal piece
- Defects in any energy metabolism pathway (glycolysis, mitochondrial oxidative phosphorylation, Krebs cycle, fatty acid oxidation) can disturb sperm motility 2
- Midpiece anomalies significantly increase the risk of motility decline: Patients with midpiece anomalies showed 33.3% vs 15.9% incidence of 1-2 hour motility decrease 3
Sperm Concentration and Quality Factors
- Lower initial sperm concentration correlates with greater motility decline: Men with decreased 1-2 hour motility had significantly lower sperm concentration (33.5 vs 79 million/mL) 3
- Morphology impacts motility stability: Percent normal morphology was significantly lower (7% vs 8%) in men with decreasing motility 3
- Men with total motile sperm count (TMSC) between 10-40 million showed significantly higher incidence of 1-2 hour motility decline (29.0% vs 14.6%) 3
Environmental and Lifestyle Factors
- Environmental toxins may contribute to declining sperm parameters including motility 4
- Obesity and poor diet have been linked to decreased sperm parameters 4
- Xenoestrogens in the environment have been hypothesized to affect male reproductive health 5
- Excessive heat exposure to testes can impair sperm quality and motility 6
- Excessive alcohol consumption is associated with lower semen quality 6
Clinical Implications
- For assisted reproduction, motility decline over time may impact treatment decisions between IUI, IVF, and ICSI 3
- Men with borderline TMSC (10-40 million) should have motility checked at both 1 and 2 hours after collection due to higher risk of significant decline 3
- For men with decreased motility, consider:
- Avoiding excessive heat exposure to testes
- Maintaining moderate alcohol consumption
- Weight loss if overweight/obese
- Antioxidant therapy for mild to moderate asthenozoospermia 6
Diagnostic Considerations
- A comprehensive semen analysis should include multiple parameters rather than single measurements 6
- Normal parameters include volume 1.5-5.0 mL, pH >7.2, and sperm concentration >20 million/mL 6
- Elevated FSH levels (>7.5 IU/L) indicate 5-13 times higher risk of abnormal semen quality 6
- Ultrasound with Doppler can assess testicular size, echotexture, and blood flow to identify underlying causes 6
Understanding these factors can help identify the cause of decreased motility and guide appropriate interventions to improve fertility outcomes.