https://www.fertstert.org/article/S0015-0282(00)01679-4/pdf

Effects of male age on semen quality and fertility: a review of the literature

BACKGROUND: An increasing number of reports suggest that chemical and physical agents in the environment, introduced and spread by human activity, may affect male fertility in humans. We investigated the relationships between exposure to environmental agents and seminal characteristics, and the concentrations of reproductive hormones in the serum of men seeking infertility treatment. METHODS: We studied 225 male partners from consecutively recruited couples, who had their first infertility consultation between 1995 and 1998, in the Litoral Sur region of Argentina, one of the most productive farming regions in the world. RESULTS: A multivariate logistic regression model showed that exposure to pesticides and solvents is significantly associated with sperm threshold values well below the limit for male fertility. We also found that men exposed to pesticides had higher serum oestradiol concentrations, and that men exposed to solvents had lower LH concentrations than non-exposed men. All of these effects were greater in men with primary infertility than in men with secondary infertility. CONCLUSION: We have shown that environmental factors contribute to the severity of infertility, and that this may worsen the effects of pre-existing genetic or medical risk factors.

/pdf/contribution-of-environmental-factors-to-the-risk-of-male-1mcic539yt.pdf

Contribution of environmental factors to the risk of male infertility

Background Although the effect of maternal age on fertility is well known, it is unclear whether paternal age also affects fertility. This cross-sectional study sought to characterize the association between age and semen quality, a well-known proxy of fertility status. Methods A convenience sample of 97 non-smoking men (aged 22-80 years) without known fertility problems was recruited from a national government laboratory. The men provided semen samples and information relating to lifestyle, diet, medical and occupational details. Semen volume (ml), sperm concentration (x10(6)/ml), total sperm count (x10(6)), motility (%), progressive motility (%) and total progressively motile sperm count (x10(6)) were measured. Results After adjusting for covariates, semen volume decreased by 0.03 ml per year of age (95% CI: -0.05, -0.01); motility decreased by 0.7% per year (95% CI: -0.92, -0.43); progressive motility decreased by 3.1% per year (95% CI: -4.5, -1.6); and total progressively motile sperm count decreased by 4.7% per year (95% CI: -7.2, -2.2). There was a suggested decrease in sperm concentration and count. The proportion of men with abnormal volume, concentration and motility was significantly increased across the age decades. Conclusions In a convenience sample of healthy men from a non-clinical setting, semen volume and sperm motility decreased continuously between 22-80 years of age, with no evidence of a threshold.

/pdf/the-association-of-age-and-semen-quality-in-healthy-men-5667wumw02.pdf

The association of age and semen quality in healthy men

BACKGROUND: In fertile populations, little is known about the association between semen parameters and time to pregnancy (TTP) METHODS: Pregnant women from Copenhagen, Edinburgh, Paris and Turku who conceived without medical intervention were asked for their TTP (942 couples), and their partners provided a semen sample The proportion of morphologically normal sperm and the multiple anomalies index (MAI, ratio of the total number of anomalies to the number of abnormal sperm) were centrally estimated We estimated rate ratios for the occurrence of a pregnancy by a discrete survival model, adjusted for sexual activity and female factors affecting fecundity RESULTS: Increasing sperm concentration influenced TTP up to 5510 6 /ml The proportion of morphologically normal sperm influenced TTP up to 39% according to David’s criteria, and this association held among the subjects with a sperm concentration >5510 6 /ml For strict criteria, the threshold value was 19% normal sperm An increase of 05 in MAI was associated with an adjusted rate ratio for the occurrence of a pregnancy of 068 (95% confidence interval: 054–085) CONCLUSIONS: These results highlight the importance of sperm morphology parameters and indicate that the effect of proportion of normal sperm on TTP may be independent of sperm concentration

/pdf/time-to-pregnancy-and-semen-parameters-a-cross-sectional-2le4nroo3j.pdf

Time to pregnancy and semen parameters: a cross-sectional study among fertile couples from four European cities

BackgroundEnvironmental toxicants are allegedly involved in decreasing semen quality in recent decades; however, definitive proof is not yet available. In 1976 an accident exposed residents in Seve...

Dioxin Exposure, from Infancy through Puberty, Produces Endocrine Disruption and Affects Human Semen Quality

A prospective study of 394 infertile men was conducted over 3 years following a primary semen analysis. The cumulative pregnancy rate was 43 and 64% after 1 and 3 years, respectively. The pregnancy rate was significantly higher in the secondary infertile group. The study of various sperm factors and the occurrence of pregnancy showed that they were not of equal significance in predicting male fertility potential. The percentage of pregnancies decreased significantly only when the sperm concentration was less than 5 x 10(6)/ml. The pregnancy rate increased significantly with the percentage of motile sperm. The percentage of sperm with normal morphology was also found to be significantly higher when a pregnancy occurred than when the couple remained infertile (43.6% vs 37.7%). In a detailed morphological analysis of the sperm, six abnormalities (microcephaly, double head, amorphous head, cytoplasmic droplet, bent tail and coiled tail) were found to be significantly more frequent when a pregnancy did not occur. The most predictive value was given by the Multiple Anomalies Index (MAI), which is the mean number of abnormalities observed per abnormal sperm. The pregnancy rate was significantly lower after both 1 and 3 years when the MAI was greater than 1.6. Multivariate analysis showed that the best prognostic indicator of fertility was given by the percentage of motile sperm and the MAI, particularly in patients with primary infertility.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2605.1988.tb01011.x

Male factors and the likelihood of pregnancy in infertile couples. I. Study of sperm characteristics

A prospective study of 394 infertile men was conducted over 3 years following a primary semen analysis. Simple comparisons between the groups of men whose partners conceived and those that did not, showed that the mean duration of infertility in the primary infertile group was significantly shorter when a pregnancy was observed, while age differed significantly between the two populations in the secondary infertile group. Multivariate analyses, taking these variables and sperm characteristics into account, showed that prognostic variables for the occurrence of pregnancy were the duration of infertility, sperm motility and the multiple anomalies index in the primary infertile group, and age of the male partner and percentage of normal sperm in the secondary infertile group. Tables for estimating the probability of observing a pregnancy as a function of these criteria are presented. In this study no positive influence of treatment on the occurrence of a pregnancy was found during the 3 years following the first semen analysis.

P. Jouannet

Papers

Male factors and the likelihood of pregnancy in infertile couples. I. Study of sperm characteristics

Male factors and the likelihood of pregnancy in infertile couples. II. Study of clinical characteristics--practical consequences