Table 3: Univariate analysis of selected risk factors for .

VariableCases ()Controls ()OR (95% CI)

Age (years)
 <3548 (55.17)56 (64.37)1.0 (Ref)0.217
 ≥3539 (44.83)31 (35.63)1.47 (0.80–2.70)
BMI (kg/m2)
 <2434 (39.08)65 (74.71)1.0 (Ref)0.002
 ≥2434 (39.08)20 (22.99)3.25 (1.63–6.48)
 Unknown19 (21.84)2 (2.30)
Age at menarche (years)
 ≤1457 (65.52)74 (85.06)1.0 (Ref)0.001
 >1430 (34.48)10 (11.49)3.90 (1.76–8.62)
 Unknown0 (0.00)3 (3.45)
Parity
 ≤164 (73.56)72 (82.76)1.0 (Ref)0.019
 >122 (25.29)9 (10.34)2.75 (1.18–6.41)
 Unknown1 (1.15)6 (6.90)
Miscarriages
 No23 (26.44)25 (28.74)1.0 (Ref)0.470
 Yes25 (28.74)36 (41.38)0.76 (0.35–1.62)
 Unknown39 (44.82)26 (29.88)
Age at birth of first child (years)
 ≤2734 (39.08)26 (29.89)1.0 (Ref)0.001
 >278 (9.20)29 (33.33)0.21 (0.08–0.54)
 Unknown45 (51.72)32 (36.78)
Duration of breastfeeding (months)
 ≤1234 (39.08)42 (48.28)1.0 (Ref)0.688
 >1236 (41.38)39 (44.83)1.14 (0.60–2.16)
 Unknown17 (19.54)6 (6.89)
History of benign breast disease
 Yes6 (6.90)3 (3.45)4.54 (1.07–19.14)0.039
 No37 (42.53)84 (95.55)1.0 (Ref)
 Unknown44 (50.57)0 (0.00)
Galactostasis
 Yes23 (26.44)32 (36.78)0.86 (0.44–1.70)0.670
 No40 (45.98)48 (55.17)1.0 (Ref)
 Unknown24 (27.58)7 (8.05)
Nipple retraction
 Yes24 (27.59)1 (1.15)32.76 (4.32–248.61)0.001
 No63 (72.41)86 (98.85) 1.0 (Ref)

Note. Data are number (%) of patients. BMI: body mass index, calculated as weight in kilograms divided by the square of height in meters. OR: odd ratio. CI: confidence interval.
binary logistic regression.