Semen Volume and Age: A Retrospective Study of 1,775 Men at KL Fertility Centre

Tham MY, Chong MK, Lee SK, Sim PK, Loke MK, Nadkarni P. Is there an association between semen volume and age? Abstract A-004. Med J Malaysia 2021;76(Suppl 3):2. Presented as a poster at the 28th International Congress of the Obstetrical and Gynaecological Society of Malaysia (OGSM 2021), 23 to 25 July 2021. KL Fertility & Gynaecology Centre, Kuala Lumpur, Malaysia.

Funding and disclosures: No funding or competing-interest declarations are reported on this poster or in the published abstract.

Semen volume is thought to fall with age. Ageing changes the genitourinary tract: seminal vesicle function weakens and the prostate changes, which leads to smooth muscle atrophy and lower protein and water content in the ejaculate.

This study aimed to determine whether semen volume is associated with the age of the man, using semen analyses recorded at one fertility centre.

This was a retrospective study of 1,775 men who had a semen analysis at KL Fertility Centre in Kuala Lumpur between January 2016 and December 2017. The authors used the World Health Organization (WHO) 5th edition semen parameters as the reference standard.

The men were divided into three age groups: 20 to 39 years, 40 to 59 years and 60 to 79 years. Semen volume per ejaculate was compared across the groups with one-way analysis of variance (ANOVA), and the relationship between age and volume was tested with Pearson correlation. The analysis was run in SPSS version 22.

The youngest man was 22 years old and the oldest was 79, with an average age of 35.88 years. Most men (78.6%, 1,395/1,775) were aged 20 to 39 years, and only 14 men (0.8%, 14/1,775) were in the oldest group.

Mean semen volume fell from 2.73 ml in the youngest group to 1.96 ml in the oldest group. The one-way ANOVA showed a statistically significant difference in semen volume between the age groups (p < 0.05). Men in the oldest group had a lower volume than both other groups (p < 0.05). The Pearson correlation also showed that volume decreased with age (R = -0.09, p < 0.01).

The correlation describes a weak linear association between age and semen volume. The square of the reported R is about 0.0081 (calculated here from the reported R), so under 1% of the variance in volume is shared with age in a linear model. The abstract does not give the information needed to judge whether the differences between age groups are clinically important.

The direction of the finding agrees with the wider literature. A systematic review and meta-analysis by Johnson and colleagues pooled 90 studies with 93,839 men and reported that semen volume declined with age, along with other semen traits such as motility and normal morphology. The present study found the same direction in a single Malaysian clinic, with a weak correlation.

Several features of the study limit direct comparison. A retrospective study of over 2,500 men by Castellini and colleagues reported that age was associated with lower motility and normal morphology after adjustment for abstinence time, smoking, accessory gland infections and varicocele. The KL Fertility Centre abstract reports no such adjustment, so its estimate cannot be separated from these other factors.

The authors name environmental, occupational, medical and lifestyle factors as possible contributors to lower semen volume and recommend that future studies examine them.

The results suggest that age is one of several factors to consider when semen volume is reviewed. They do not show that age alone predicts a low volume in an individual man, because the correlation is weak and the oldest group is small.

The study was done at one centre in men who attended for a semen analysis, so the results may not apply to the general male population in Malaysia. Only 14 men were in the oldest group, which makes the estimate for that group less certain.