Semen and sperm reference ranges for men 45 years of age and older

The most widely used reference values for human semen and sperm variables were developed by the World Health Organization (WHO) to help assess the fertility status of men interested in reproduction (typically a younger population). In this retrospective analysis, data from a large population of men aged 45 years or older were analyzed to derive semen and sperm reference ranges for an older population. Baseline semen samples were obtained from 1174 men with no or mild erectile dysfunction (ED) during the screening phase of two clinical trials evaluating the effects of a drug on human spermatogenesis. The median values and 95% reference ranges for 4 measured semen and sperm parameters (semen volume, sperm concentration, sperm motility, and sperm morphology) and 1 derived parameter (total sperm count) were calculated for the population and by age quartile. These references ranges were compared to established WHO reference values. Associations between the semen and sperm parameters and smoking status, alcohol use, and serum hormone concentrations were also analyzed. The mean age was 52.9 years (range: 45-80). Median semen volume, sperm motility, and sperm morphology parameters declined significantly with age. Only 46% of study subjects had baseline values for semen and sperm parameters that met or surpassed all the WHO reference values. This is the first study to statistically derive semen reference ranges from a large population of men aged 45 years or older. The observation that less than half the men in this study met all 4 WHO reference values for measured semen and sperm parameters underscores the need for age-specific reference ranges.