This study clearly demonstrates an increase in sperm double-stranded DNA breaks with age.

1: Fertil Steril. 2003 Dec;80(6):1420-30. Links
Effects of age on DNA double-strand breaks and apoptosis in human sperm.Singh NP, Muller CH, Berger RE.
Department of Bioengineering, University of Washington, Seattle, Washington 98195-7962, USA. narendra@u.washington.edu

OBJECTIVE: This study was designed to explore the relationship between men's age and DNA damage and apoptosis in human spermatozoa. DESIGN: Semen samples were collected from men between the ages of 20 and 57 years. Sperm DNA double-strand breaks were assessed using the neutral microgel electrophoresis (comet) assay, and apoptosis was estimated using the DNA diffusion assay. SETTING: Academic medical center. PATIENT(S): Sixty-six men aged 20 to 57 years were recruited from infertility laboratory and general populations and consented to donate a semen sample. Recruitment was determined by time and day of analysis; the only exclusions were for azoospermia, prostatitis, or prior cancer therapy. INTERVENTION(S): None. MAIN OUTCOME MEASURE(S): DNA damage and apoptosis in human sperm. RESULT(S): Age correlated with an increasing percentage of sperm with highly damaged DNA (range: 0-83%) and tended to inversely correlate with percentage of apoptotic sperm (range: 0.3%-23%). For example, percentage of sperm with highly damaged DNA, comet extent, DNA break number, and other comet measures was statistically significantly higher in men aged 36-57 years than in those aged 20-35 years, but percentage apoptosis was statistically significantly lower in the older group. Semen analysis showed percentage motility to be significantly higher in younger age groups. CONCLUSION(S): This study clearly demonstrates an increase in sperm double-stranded DNA breaks with age. Our findings also suggest for the first time an age-related decrease in human sperm apoptosis. These novel findings may indicate deterioration of healthy sperm cell selection process with age.

PMID: 14667878 [PubMed - indexed for MEDLINE]