Potential Confounders - Male
Personal characteristics (paternal age)
Medical conditions (recent infection, gonadal trauma, impaired immune status, high fever, mumps orchitis, diabetes, prostatitis, varicocele, hydrocele)
Drugs (marijuana, estrogen, chlorambucil, cyclophosphamide, nitrofurantoin)
Personal habits (tobacco, alcohol, frequent saunas, hot tub use, tight briefs
Environmental/occupational hazard (solvents, metals, pesticides, excess heat, ionizing radiation, neurotoxicants