Fig. 3

The associations of GSTT1, GSTM1 and GSTT1TM1 gene polymorphisms with sperm parameters (binary categorical variable). The logistic regression model was applied adjusting for age (continuous), BMI (continuous), smoking (categorical) and drinking status (categorical). GSTT1TM1 was a multicategory variable and the reference group was GSTM1− and GSTT1−.