Temporal trends in sperm count: a systematic review and meta-regression analysis

AbstractBACKGROUNDReported declines in sperm counts remain controversial today and recent trends are unknown. A definitive meta-analysis is critical given the predictive value of sperm count for fertility, morbidity and mortality.OBJECTIVE AND RATIONALETo provide a systematic review and meta-regression analysis of recent trends in sperm counts as measured by sperm concentration (SC) and total sperm count (TSC), and their modification by fertility and geographic group.SEARCH METHODSPubMed/MEDLINE and EMBASE were searched for English language studies of human SC published in 1981 –2013. Following a predefined protocol 7518 abstracts were screened and 2510 full articles reporting primary data on SC were reviewed. A total of 244 estimates of SC and TSC from 185 studies of 42 935 men who provided semen samples in 1973–2011 were extracted for meta-regression analysis, as wel l as information on years of sample collection and covariates [fertility group (‘Unselected by fertility’ versus ‘Fertile’), geographic group (‘Western’, including North America, Europe Australia and New Zealand versus ‘Other’, including South America, Asia and Africa), age, ejaculat ion abstinence time, semen collection method, method of measuring SC and semen volume, exclusion criteria and indicators of completeness of covariate data]. The slopes of SC and TSC were estimated as functions of sample collection year using both simple linear regression and weighted meta-regression models and t...
Source: Human Reproduction Update - Category: OBGYN Source Type: research