LAUSR

The Importance of Being Earnest: The Impact of Meta-analyses in Real-life Everyday Clinical Practice The meta-analysis by Sharma et al. [1] provides a comprehensive analysis of the impact of cigarette smoking on semen parameters assessed according to the most recent World Health Organization (WHO) 2010 laboratory criteria [2]. After a thorough analysis of data for 5865 patients, the authors concluded that cigarette smoking is associated with reduced sperm count and motility. Although the detrimental impact of cigarette smoking on semen parameters is widely acknowledged, the results of this meta-analysis provide novel insights in the context of changes brought by the introduction of the WHO 2010 criteria. Some of the issues involved deserve discussion. First, nine of the 14 studies considered for the analyses assessed the effects of cigarette smoking among infertile men alone, whereas the remaining five included fertile men as well. Of importance, several other factors for infertile men might disguise the effects of cigarette smoking overall; putting together fertile and infertile men without apparent discrimination may undermine the possible conclusions of the meta-analysis. When trying to assess effects on semen parameters in the male infertility setting, this issue is fundamentally important: in 2006 a Cochrane review and a subsequent meta-analysis including more homogeneous studies [3] came to completely opposite conclusions regarding the effects of varicocele treatment. Although the authors make a clear distinction between infertile men and general samples, a difference reported in the general population (as detected in a population-based cohort, for example) usually reflects a major pathologic role of smoking in general health, whereas results from cross-sectional studies mirror eventual observations in real-life clinical practice. Second, as stated by the authors, introduction of the 2010 WHO standards mainly impacted the evaluation of