New evidence of the influence of exogenous and endogenous factors on sperm count in man

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Abstract

Objective: To examine the association between individual exposures due to occupation, environment and lifestyle on sperm count, we conducted a case-control study among 92 fertile and 73 sub-fertile Caucasian males. Study Design: Data from questionnaires were analysed using simple univariate and multivariate logistic regression models. Results: At risk for oligozoospermia are men exposed to pesticides (odds ratio (OR) 8.4; 95% confidence interval (CI) 1.3–52.1), welding (OR 2.8; CI 0.9–8.7), antibiotic use (OR 15.4; CI 1.4–163), a history of mumps (OR 2.9; CI 1.3–6.7), gastrointestinal complaints (OR 6.2; CI 1.4–26.8), decreased intake of fruits (OR 2.3; CI 1.0–5.1), vegetables (OR 1.9; CI 0.7–5.0), or with female fertility disorders in their families (OR 8.4; CI 1.7–41.9). Unlike other studies, no associations were observed between oligozoospermia and exposure to paint or heat. Conclusion: This study suggests new risk factors oligozoospermia in man and confirms previously reported results from others.

Introduction

Environmental and occupational exposures, such as xeno-estrogens, pesticides, heat and paint, are suggested to have a detrimental effect on male fertility [1], [2], [3]. The well-known endocrine disrupter, 1,2-dibromo-3-chloropropane (DBCP; a nematocide), has been reported to damage the seminiferous tubules and to affect the sperm count as demonstrated by Whorton et al. [1] in agricultural workers on the banana plantations of Costa Rica. Welch et al. [2] reported that shipyard painters exposed to ethylene glycol ethers have an increased prevalence of oligozoospermia and azoospermia. Adverse effects of occupational heat and smoke exposure on sperm morphology have been found in welders by Bonde [4] whereas other studies did not [5]. Lifestyle factors such as smoking, alcohol intake, heat exposure (hot tub; sauna), and malnutrition (fruits and vegetables) are increasingly gaining interest in relation to sub-fertility [6], [7], [8]. Little attention has been paid to the impact of the nutritional status on male fertility. Animal and human studies have shown that vitamins C–E and other micronutrients such as selenium and zinc could influence spermatogenesis [9], [10], [11], [12]. However, details on the underlying mechanisms are not known.

Reduced fertility has been detected among males exposed to specific antibiotics such as sulphasalazine, and infectious diseases [13], [14], [15]. Sulpha-preparations are commonly used in gastrointestinal inflammatory diseases such as Crohn’s disease. These and other gastrointestinal diseases, such as coeliac sprue, characterised by the presence of diarrhoea and nutritional deficiencies due to malabsorption, have also been reported in relation to male factor sub-fertility [16].

Besides occupational, lifestyle and environmental exposures as risk factors for male factor sub-fertility, genetic factors also play a part [17]. Because of the multifactorial pathogenesis of male factor sub-fertility the present case-control study focused on males with medically diagnosed sub-fertility to examine potential risks associated with occupational and environmental exposures, lifestyle, nutritional exposures, as well as medical history and family history of fertility problems.

Section snippets

Materials and methods

For this study, we analysed pre-intervention data from our previously performed randomised controlled trial in which the effect of extra folate and/or zinc administration is investigated on semen quality of fertile and sub-fertile males [18]. Ninety-two fertile (mean (S.D.) age 34.1 (4.0) years) and 73 sub-fertile (34.4 (4.1) years) Caucasian males were included and evaluated. This sample size was calculated to be sufficient to detect an Odds ratio of 2.5 with an α of 5% and a power of 80%

Results

Table 1 presents the fertility characteristics of cases and controls. As expected, sub-fertile males had lower sperm motility and lower sperm count while the percentage of abnormal spermatozoa was higher when compared to fertile males.

Table 2 shows the ORs after univariate analysis for all potential risk factors in each of the five risk factor domains.

Discussion

Our study suggests that antibiotic use during the last 3 months before sampling is a risk factor for oligozoospermia in man with the highest OR of 15.4 (95% CI 1.4, 163). Doxycycline and penicillin were the most frequently reported antibiotics in this population, mainly for respiratory diseases such as pneumonia. Adverse effects of specific antibiotics such as nitrofurans, macrolides, aminoglycosides, tetracyclines, and sulpha drugs on spermatogenesis or sperm function have been reported

Acknowledgements

This work was financially supported by the Dutch ‘Praeventiefonds’/Zorg Onderzoek Nederland (ZON) (grant no. 28.2877), The Hague, The Netherlands. Thanks are due to the staff and technicians of the Central Chemistry Laboratory, the Fertility Laboratory, and the laboratory of the Department of Chemical Endocrinology, the University Medical Centre, Nijmegen, for expert technical assistance; to Mrs. Nelleke J. Hamel for assistance in data collection and the staff of the fertility clinic (head:

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