Association of semen quality and occupational factors: comparison of case-control analysis and analysis of continuous variables

Fertil Steril. 1998 Jan;69(1):11-8. doi: 10.1016/s0015-0282(97)00437-8.


Objective: To compare two statistical approaches, case-control and analysis of continuous parameters of semen, in examining the relationship between occupational exposures and male reproductive function.

Design: Case-control study.

Setting: Males providing semen samples at a university infertility clinic.

Patient(s): Nonvasectomized males who provided at least one semen sample at an infertility clinic.

Main outcome measure(s): Standard clinical semen analysis.

Result(s): Analyses using a dichotomous dependent variable did not uncover significant associations between any occupational factor and infertility case status. However, linear models incorporating continuous variables identified a number of occupational factors that were associated with specific parameters of semen. A reduction in percentage of progressive sperm and an increase in percentage of coiled tail sperm defects in welders, compared with unexposed subjects, were found. Significant dose-response relationships between level of perceived job stress and percentage of progressive sperm, total motile count, morphology, abnormal heads, and coiled tail defects were found.

Conclusion(s): The findings suggest that subtle changes in semen variables, possibly associated with workplace exposure, may be detected only with parametric analyses of continuous variables of semen.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Case-Control Studies
  • Humans
  • Infertility, Male / etiology*
  • Infertility, Male / physiopathology*
  • Male
  • Middle Aged
  • Occupations*
  • Semen / physiology*
  • Statistics as Topic / methods
  • Stress, Physiological / physiopathology
  • Surveys and Questionnaires