Association between lifestyle factors and semen parameters: An overview of systematic reviews

Abstract

Infertility, defined as inability of a couple to conceive after a year of unprotected regular intercourse, with third of cases due to suboptimal sperm quality. There are modifiable and nonmodifiable risk factors that can affect the quality and quantity of sperm and hence fertility. Several separate systematic reviews exist on this topic and clinicians are often faced with a plethora of reviews with variable quality giving conflicting advice. Therefore, we summarized the current available data by conducting a systematic review of systematic reviews on risk factors such as coffee/caffeine, body mass index (BMI)/obesity, cigarette smoking, and paternal age, on sperm parameters of count, motility, and morphology so that all evidences are present together, at one place. Embase, OVID MEDLINE(R), and Cochrane central database of systematic review were searched for relevant publications between 2010 and present. Search terms were: smoking, obesity, obese, BMI, caffeine, paternal age, advanced paternal age, male infertility, male fertility, sperm motility, sperm quality, and sperm analysis. Systematic reviews that met the criteria were retrieved and the relative reference lists were searched. All included studies were quality assessed using the AMSTAR checklist tool. Electronic and manual hand search yielded a total of 318 studies, of which 11 were excluded after removing duplicates and a further 286 excluded based on titles and abstract. Full-text screening of 21 articles, excluded 10 further studies. Eleven publications were finally included. Obesity and smoking were associated with decline in sperm count and morphology, age with decline in motility and morphology. Caffeine consumption was not associated with changes in any of the three parameters. Obesity and smoking are modifiable risk factors impacting on the semen parameters; caffeine consumption may not have any adverse effects on sperm parameters. This overview was limited by the quality of included reviews which in turn were limited by observational nature of the included studies, small numbers, and heterogeneity of the population. Further prospective data collection is needed to have good quality evidence. In conclusion, high BMI, smoking, and advanced paternal age were found to be associated with decline in one or more parameters of semen quality in males, albeit the evidence is of varying strength. Caffeine was not associated with any deterioration.