AUTHOR=Zhao Jing , Lu Qing-Bin , Li Hao , Yuan Yang , Cui Ning , Yuan Chun , Zhang Xiao-Ai , Yang Zhen-Dong , Ruan Shi-Man , Liu Lan-Zheng , Du Juan , Fang Li-Qun , Liu Wei 

TITLE=Sex Differences in Case Fatality Rate of Patients With Severe Fever With Thrombocytopenia Syndrome

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.738808

DOI=10.3389/fmicb.2021.738808

ISSN=1664-302X

ABSTRACT=Background: Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne disease with high mortality. However, a disaggregated data has been lacking to explore the effect of sex on the mortality.
Methods: A retrospective cohort study was performed among 2,938 SFTS patients entered during 2011-2020 in Xinyang, China. The case fatality rate (CFR) was estimated for their association with sex, age and comorbidities by an interactive way. The difference of immune response between sex was explored in an age dependent way.
Results: An overall CFR of 15.3% (450/2,938) was obtained, which appeared to be higher in males than in females [17.7% vs. 13.6%, adjusted odds ratio (aOR): 1.24; 95% CI, 1.00-1.53; P = 0.048] and increased dramatically with age (P <0.001). The associations between sex and SFTS fatal outcome were age-dependent and varied according to the status of comorbidities. The differential risk conferred by older age was more pronounced in males than females, with aOR and 95% CI to be 5.76 (3.75-8.84) vs. 5.30 (3.54-7.95). Sex-stratified analysis disclosed significant associations between death and comorbidities for females (aOR,1.87, 95% CI: 1.40-2.49; P <0.001), while no effect in males. Among females, the significant association with fatal outcome differed among age groups, with aOR (95% CI) reduced from 2.28 (1.16-4.46) in ≤60 years old, to 2.06 (1.34-3.18) in 60-70 years old and further to 1.55 (0.97-2.47) in >70 years old. Altogether 194 SFTS patients were randomly selected for the test of B cells, natural killer (NK) cells, CD4 cells percentages and anti-SFTSV IgM antibody level, which revealed that males >60 years old had significantly decreased percentages of B cells, CD4 cells, lower anti-SFTSV IgM antibody titer, and increased level of NK cells than those ≤60 years old, while none of these age specific differences was observed in the females.
Conclusions: Males had a significantly higher mortality of SFTS than did females, and more likely to be affected by aging for SFTS mortality. This difference can be explained by the effect from comorbidities and the host immunity. It is essential to take a sex- and age-based approach to SFTS treatment and management.