Age-specific sex-related differences in infections: a statistical analysis of national surveillance data in Japan

PLoS One. 2012;7(7):e42261. doi: 10.1371/journal.pone.0042261. Epub 2012 Jul 27.


Background: To prevent and control infectious diseases, it is important to understand how sex and age influence morbidity rates, but consistent clear descriptions of differences in the reported incidence of infectious diseases in terms of sex and age are sparse.

Methods and findings: Data from the Japanese surveillance system for infectious diseases from 2000 to 2009 were used in the analysis of seven viral and four bacterial infectious diseases with relatively large impact on the Japanese community. The male-to-female morbidity (MFM) ratios in different age groups were estimated to compare incidence rates of symptomatic reported infection between the sexes at different ages. MFM ratios were >1 for five viral infections out of seven in childhood, i.e. male children were more frequently reported as infected than females with pharyngoconjunctival fever, herpangina, hand-foot-and-mouth disease, mumps, and varicella. More males were also reported to be infected with erythema infectiosum and exanthema subitum, but only in children 1 year of age. By contrast, in adulthood the MFM ratios decreased to <1 for all of the viral infections above except varicella, i.e. adult women were more frequently reported to be infected than men. Sex- and age-related differences in reported morbidity were also documented for bacterial infections. Reported morbidity for enterohemorrhagic Escherichia coli infection was higher in adult females and females were reportedly more infected with mycoplasma pneumonia than males in all age groups up to 70 years.

Conclusions: Sex-related differences in reported morbidity for viral and bacterial infections were documented among different age groups. Changes in MFM ratios with age may reflect differences between the sexes in underlying development processes, including those affecting the immune, endocrine, and reproductive systems, or differences in reporting rates.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Age Distribution
  • Aged
  • Bacterial Infections / epidemiology*
  • Child
  • Child, Preschool
  • Data Interpretation, Statistical*
  • Female
  • Humans
  • Infant
  • Infant, Newborn
  • Japan
  • Male
  • Middle Aged
  • Models, Statistical
  • Population Surveillance / methods*
  • Sex Distribution
  • Viral Vaccines / immunology
  • Virus Diseases / epidemiology*
  • Virus Diseases / prevention & control
  • Young Adult


  • Viral Vaccines

Grant support

This work was supported in part by a Grant-in-Aid for Scientific Research (C) #22500260 to NE from the Japan Ministry of Education, Culture, Sports, Science and Technology. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. No additional external funding was received for this study.