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

Table 1 Distribution of selected characteristics between cases and fertile controls

Variables	Controls (n = 480)	Case 1^a (n = 524)		Case 2^b (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

^aCase 1: idiopathic infertile men with azoospermia or oligozoospermia.
^bCase 2: idiopathic infertile men with normal sperm count.
^cAmong ever smokers.
^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).
n. d.: not detected.

ISSN: 1741-7015