Semen quality among Danish and Finnish men attempting to conceive

Objective: To assess differences in semen quality between similar populatio ns from Denmark and Finland. Design: Comparison of semen quality between 221 Finnish men (of whom 115 ha d no proven fertility) and 411 Danish men with no proven fertility in two f ollow-up studies among normal couples trying to conceive. Methods: In Finland male partners of couples without experienced infertilit y attempting to conceive were recruited through advertisements in local new spapers from 1984 to 1986. From 1992 to 1995 Danish men who lived with a pa rtner and who had not attempted to achieve a pregnancy previously were recr uited through their union when they discontinued birth control. All semen a nalyses were performed in accordance with the World Health Organization gui delines. Results: Median sperm concentration, total sperm count and the percentage o f morphologically normal spermatozoa were significantly higher among the Fi nnish men without proven fertility (104.0 million/ml, 304.0 million and 58% respectively) compared with the Danish men (53.0 million/ml, 140.8 million , and 41% respectively), Sperm concentration was 105.7% (95% confidence int erval (CI) 58.1%-167.6%) and total sperm count was 127.4% (95% CI 71.4%-201 .6%) higher among Finnish men without proven fertility than among Danish me n after control for confounders. Conclusions: Some, but hardly all, of the observed difference in semen qual ity may be explained by differences in recruitment procedures, selection of the men and by methodological differences in semen analysis between the tw o countries, Also a birth cohort effect may explain some of the differences between countries as the Finnish men were recruited 11 years before the Da nish men. Therefore, follow-up studies with identical recruitment and selec tion of men from the two countries are needed.