A meta-analytic evaluation of sex differences in meningococcal disease incidence rates in ten countries.

The magnitude and consistency of the sex differences in meningococcal disease incidence rates (IR) have not been systematically examined in different age groups, countries and time-periods. We obtained national data on meningococcal disease incidence rates by sex, age group and time period, from ten countries. We used meta-analytic methods to combine the male to female incidence rate ratios (IRRs) by country and year for each age group. Meta-regression analysis was used to assess the contribution of age, country and time period to the variation in the IRRs. The pooled male to female IRRs (with 95% CI) for ages 0-1, 1-4, 5-9, 10-14 and 15-44, were 1.25 (1.19-1.32), 1.24 (1.20-1.29), 1.13 (1.07-1.20), 1.21 (1.13-1.29) and 1.15 (1.10-1.21) respectively. In the age groups 45-64 and over 65, the incidence rates were lower in males with IRRs of 0.83 (0.78-0.88) and 0.64 (0.60-0.69), respectively. Sensitivity analysis and meta-regression confirmed that the results were robust. The excess meningococcal incidence rates in young males and the higher rates in females at older ages were consistent in all countries, except the Czech Republic. While behavioral factors could explain some of the sex differences in the older age groups, the excess rates in very young males suggest that genetic and hormonal differences could be important.