Sex difference in infant mortality: a study of UK Paediatric Intensive Care admissions over 11 years
Abstract Rationale Within the UK, child mortality from all causes has declined for all ages over the last three decades. However, distinct inequality remains, as child mortality rates vary by sex and are generally found to be higher in males. A significant proportion of childhood deaths in the UK occur in Paediatric Intensive Care Units (PICU). Objectives We aimed to study the association of sex with infant mortality in PICUs. Methods We obtained data for all infant admissions to UK-PICUs from 01/01/2005 to 31/12/2015. We assessed the causal relationship between sex and mortality and selected appropriate variables for adjustment. We fitted a cause specific hazard ratio (CSHR) model, and a logistic model to estimate the adjusted effect of sex on mortality in PICU. Pre-defined subgroups were children less than 56 days old, and those with a primary diagnosis of infection. Measurements and Main Results Within the 71,243 admissions, there were 1,411/29,520 (4.8%) female deaths, and 1,809/41,723 (4.3%) male deaths. The adjusted male to female CSHR was 0.87 (95%-CI 0.81 to 0.92) representing a 13% higher risk of death for females over males. Similarly, the adjusted OR for male to female mortality is 0.87 (95%-CI, 0.81 to 0.94). Subgroup analysis yielded similar findings. Conclusions Female sex is associated with higher mortality in infants needing PICU admission, despite similar severity of illness to males. There was no effect of age or infection status. This suggests that females and males differ in the pathophysiology of critical illness and/or their response to treatment.