Semen quality of young men from the general population in Baltic countries

Abstract

Study question: What are the parameters of semen quality in Baltic men?

Summary answer: Combined parameters of sperm concentration, motility and morphology revealed that 11-15% of men had low semen quality, 37-50% intermediate and 38-52% high semen quality.

What is known already: Previous studies have revealed regional differences in semen parameters, and semen quality of Baltic men has been suggested to be better than that of other European men.

Study design, size, duration: This was a cross-sectional study of 1165 men aged 16-29 years from Estonia (N = 573), Latvia (N = 278) and Lithuania (N = 314) conducted in 2003-2004.

Participants/materials setting methods: Men from the general population, median age 19.8 years, provided one semen sample each, had blood samples taken, had testis size determined, and provided information on lifestyle. Based on combined data of sperm concentration, sperm motility and morphology the cohort was classified into three categories: low, intermediate or high semen quality. Comparisons between groups (including subgroups of Estonian men of Russian versus Estonian ethnicity) were tested, adjusting for ejaculation abstinence and age.

Main results and the role of chance: The median sperm concentration of the Estonian, Latvian and Lithuanian populations of Baltic men was 63 mill/ml. Low semen quality was detected in 11-15% of the men, intermediate in 37-50% and high in 38-52%. No crucial differences between national subgroups were detected, except that a higher percentage (9.6%) of the subgroup of Russian Estonians reported having had cryptorchidism compared to the other men (2.5-3.6%, P < 0.001). Smoking had an adverse impact on both sperm concentration and total sperm counts (P < 0.001).

Limitations reasons for caution: The semen quality data were collected >10 years ago. Thus, a recent change in semen quality cannot be excluded. Owing to the study design, it is assumed, but unproven, that the men were representative of the general populations. Some men were very young (16 years), however, this was also the case for other European studies of similar populations. Assessment of sperm motility is associated with inter-observer variation, and no quality control was undertaken for sperm motility assessment to account for that. Thus, estimates of sperm motility should be interpreted with caution.

Wider implications of the findings: Analysis of the semen variables separately did not identify that a considerable percentage of Baltic men had low semen quality. The combined analysis, however, showed that more than one out of nine men had semen quality at a level indicating reduced fertility chances. We suggest that future studies of semen quality should be carried out reporting both results of single semen parameters and estimates that combine the most frequently assessed variables.

Study funding/competing interest(s): The study was funded by the EU fifth framework project Number QLK4-1999-01422 'Envir.Repro.Health' extension to Baltic countries Number QLRT-2001-02911; Estonian Science Foundation, grant numbers 2991 and PUT181. There are no competing interests.

Trial registration number: N/A.

Keywords: fertility; general populations; regional differences; semen quality; young men.