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Table 1 Distribution of selected characteristics between cases and fertile controls

From: Common variants in mismatch repair genes associated with increased risk of sperm DNA damage and male infertility

Variables Controls
(n = 480)
Case 1a
(n = 524)
Case 2b
(n = 768)
  N (%) N (%) P d N (%) P d
Age (mean ± SEM) 28.1 ± 0.16 28.3 ± 0.16 0.374 28.3 ± 0.14 0.355
Smoking stauts      
Never 278 (57.9) 238 (45.4) < 0.001 363 (47.3) < 0.001
Ever 202 (42.1) 286 (54.6)   405 (52.7)  
Pack-years (mean ± SEM)c 4.3 ± 0.21 5.2 ± 0.20 0.002 4.9 ± 0.14 0.014
Drinking status      
Never 425 (88.5) 447 (85.3) 0.129 667 (86.8) 0.377
Ever 55 (11.5) 77 (14.7)   101 (13.2)  
Semen parameters (mean ± SEM)      
Concentration (× 106 /ml) 102.6 ± 3.07 5.12 ± 0.38 < 0.001 73.6 ± 2.12 < 0.001
Motility (%) 65.3 ± 0.58 3.26 ± 0.27 < 0.001 37.9 ± 0.55 < 0.001
Volume (ml) 2.80 ± 0.07 2.37 ± 0.07 < 0.001 2.78 ± 0.05 0.818
Sperm DNA fragmentation (%) n. d. n. d.   19.5 ± 0.82  
  1. aCase 1: idiopathic infertile men with azoospermia or oligozoospermia.
  2. bCase 2: idiopathic infertile men with normal sperm count.
  3. cAmong ever smokers.
  4. d P-values were derived from the χ2 test for categorical variables (smoking and drinking status) and t test for continuous variables (age and pack-years).
  5. n. d.: not detected.