Meta AnalysisHumann = 190 studies2023
Lifestyle-, environmental-, and additional health factors associated with an increased sperm DNA fragmentation: a systematic review and meta-analysis.
Plain-language summary
This systematic review and meta-analysis set out to find which lifestyle, environmental and health factors go with higher sperm DNA fragmentation, meaning breaks in the genetic material inside sperm, where more breaks mean a lower chance of conception. It pooled 190 studies and calculated the mean difference in fragmentation between men with and without each exposure. Varicocele and impaired glucose tolerance had the largest effects, raising fragmentation by 13.62 and 13.75 percentage points. Being over 50 added 12.58 points, testicular tumors up to 11.3, pollution 9.68 and smoking 9.19. Chlamydia and HPV made almost no difference, and neither did how long a man abstained before the sample.
Key findings
- Varicocele (enlarged veins in the scrotum) raised sperm DNA fragmentation by 13.62 percentage points.
- Impaired glucose tolerance (early blood sugar dysregulation) raised it by 13.75 percentage points.
- Age from 50 onwards added 12.58 percentage points, testicular tumors up to 11.3, pollution 9.68 and smoking 9.19.
- For Chlamydia and HPV infections, and for how long a man abstained before giving the sample, no relationship was found.
How to analyze the study yourself
- Study type
- Meta-analyses pool data from many studies to spot patterns, but they rely on the quality of the original studies and cannot prove cause and effect.
- Population
- Men from various studies, with and without the studied exposures.
- Funding
- Not reported
- Takeaway
- This review found that varicocele and early blood sugar trouble raised sperm DNA damage most, by about 13 percentage points each, with age over 50, testicular tumors, air pollution and smoking behind them, while for infections and for abstinence length no relationship was found. Smoking, diet and exercise (to improve blood sugar), and air quality are the ones on that list you can change this week. If you already know you have a varicocele, it may be worth asking your doctor whether repair is on the table for you, because it is the only item here with a procedure attached.