Table 1 Characteristics of the study population (n = 1243).

Characteristic	Control (n = 410)^a	Case Group I (n = 191)^b	Case Group II (n = 642)^c	Subgroup I (n = 122)^d	Subgroup II (n = 340)^e	Subgroup III (n = 311)^f	Subgroup IV (n = 611)^g
Age (mean ± SD)	29.90 ± 3.61	29.19 ± 3.91	29.11 ± 4.51	29.39 ± 4.86	29.15 ± 4.54	29.11 ± 4.59	29.13 ± 4.45
BMI (mean ± SD)^h	23.77 ± 2.94	23.23 ± 2.92	23.27 ± 3.11	23.48 ± 3.13	23.14 ± 3.11	23.12 ± 3.12	23.26 ± 3.14
Smoking status [n (%)]
Never smoker	186 (45.4)	84 (44.0)	305 (47.5)	48 (39.3)	142 (41.8)	127 (40.8)	294 (48.1)
Ever smoker	224 (54.6)	107 (56.0)	337 (52.5)	74 (60.7)	198 (58.2)	184 (59.2)	317 (51.9)
Current smoker	199 (48.5)	90 (47.1)	288 (44.9)	66 (54.1)	169 (49.7)	155 (49.8)	268 (43.9)
Former smoker	25 (6.1)	17 (8.9)	49 (7.6)	8 (6.6)	29 (8.5)	29 (9.3)	49 (8.0)
Pack-years (mean ± SD)^f	4.58 ± 4.70	5.28 ± 4.15	5.33 ± 5.80	5.92 ± 7.79	5.30 ± 6.04	5.43 ± 6.23	5.25 ± 5.81
Drinking status [n (%)]
Never drinker	187 (45.6)	99 (51.8)	290 (45.2)	56 (45.9)	148 (43.8)	137 (44.1)	274 (44.8)
Ever drinker	223 (54.4)	92 (48.2)	387 (60.3)	66 (54.1)	192 (56.5)	174 (55.9)	337 (55.2)
Current drinker	211 (51.5)	74 (38.7)	292 (45.5)	53 (43.3)	163 (47.9)	147 (47.3)	280 (45.8)
Former drinker	12 (2.9)	18 (9.4)	95 (14.8)	13 (10.7)	29 (8.5)	27 (8.7)	57 (9.3)

SD, standard deviation; BMI, body mass index.
^aProven fertility men with semen volume ≥ 2 ml, sperm concentration ≥20 × 10⁶/ml, sperm number per ejaculum ≥40 × 10⁶/ml and sperm motility ≥50% motile sperm.
^bIdiopathic infertile men with all four semen parameters at or above the WHO reference value.
^cIdiopathic infertile men with at least one of the abnormal semen parameters (semen volume, sperm concentration, sperm number per ejaculum and sperm motility).
^dIdiopathic infertile men with semen volume < 2 ml.
^eIdiopathic infertile men with sperm concentration <20 × 10⁶/ml.
^fIdiopathic infertile men with sperm number per ejaculum <40 × 10⁶/ml.
^gIdiopathic infertile men with sperm motility <50% motile sperm.
^hBMI: kg/m².

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