Photo Credit: iStock.com/Artur Plawgo

Female sex was linked to higher 30- and 90-day mortality after Staphylococcus aureus bacteremia, possibly due to immune or care-related sex differences.

Female sex was associated with greater all-cause mortality among patients with Staphylococcus aureus bacteremia (SAB). Researchers reported their findings in a Research Letter in JAMA Network Open.

“A recent systematic review and meta-analysis reported female sex was associated with increased SAB mortality, with female patients at 18% increased odds of death compared with male patients. Attempting to corroborate this apparent sex disparity, we reanalyzed data from our own nationwide study of mortality among adults with SAB in Wales, UK,” wrote coauthors Jonathan Underwood, MBBS, PhD, and Bethan L. Carter, MB, BCh.

The study included data from 7,515 adults with SAB diagnosed between April 1, 2010, and March 31, 2022, obtained from the SAIL Databank at Swansea University. Researchers analyzed anonymized electronic health record data to compare all-cause mortality within 30 and 90 days for 2,760 female and 4,755 male patients.

Overall mortality rates at 30 days after SAB were 29% for female patients and 27% for male patients. At 90 days after SAB, overall mortality rates were 37% for female patients and 36% for male patients.

Unadjusted models indicated female sex was linked with higher all-cause mortality at 30 days (odds ratio [OR], 1.12; 95% CI, 1.01-1.24; P=0.03) but not at 90 days (OR, 1.07; 95% CI, 0.97-1.18; P=0.20), researchers reported.

However, in models adjusted for baseline covariates that included age, hospital or community onset, methicillin sensitivity, comorbidities, relative regional deprivation, and frailty, female sex was associated with higher all-cause mortality at both 30 days (OR, 1.19; 95% CI, 1.06-1.34; P=0.003) and 90 days (OR, 1.15; 95% CI, 1.03-1.29; P=0.02).

In particular for 30-day mortality, female sex was linked with SAB deaths caused by sepsis (hazard ratio, 1.21; 95% CI, 1.02-1.44; P=0.03), as determined by a competing risks regression model.

Researchers hypothesized that greater mortality from sepsis and higher C-reactive protein could suggest sex-based differences in immune response to SAB. Other explanations could include sex-based differences in SAB source, healthcare-seeking behaviors, or healthcare delivery.

“Further research is necessary to investigate underlying pathophysiological, social, and health care–related factors that underpin sex-related mortality differences in SAB,” the authors wrote. “Addressing these disparities could lead to more targeted therapies, improved survival rates, and more equitable health care outcomes for both sexes.”