Time-related changes in sex distribution of COVID-19 incidence proportion in Italy

BACKGROUND: Variable sex-disaggregated data on Coronavirus disease 2019 (COVID-19) incidence proportion (IP) have been reported in different datasets and studies. Factors explaining the inconsistent distribution of COVID-19 among sexes are still unclear. OBJECTIVES: This study aimed to analyse time-related variation of sex-disaggregated COVID-19 IP in Italy since March 9(th) to May 11(th) 2020, and to test its association with the frequency of swab testing for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). STUDY DESIGN: Sex-disaggregated data on COVID-19 cases were collected from Italian publicly accessible databases along with undisaggregated data on the number of reverse transcriptase–polymerase chain reaction (RT-PCR) SARS-CoV-2 tests. Crude and adjusted associations between the frequency of RT-PCR SARS-CoV-2 testing and male-to-female (M/F) ratio of COVID-19 IP were performed. RESULTS: COVID-19 IP increased progressively in both sexes. Sex prevalence of COVID-19 IP reversed over time, with the M/F ratio of COVID-19 IP having passed from 1,73 to 0,91. The mean number of daily swabs for RT-PCR SARS-CoV-2 test increased progressively until reaching a plateau in the last three weeks of the study period. The M/F ratio of COVID-19 IP inversely correlated with the number of daily swabs for RT-PCR SARS-CoV-2 test (r = -0,87, p < 0.001), even after adjusting for the median age of COVID-19 cases (β = -0,66, p < 0,001). CONCLUSIONS: Time-related changes of sex distribution of COVID-19 IP in Italy are strongly influenced by the number of swabs testing for SARS-CoV-2. Whether gender-related disparities in the access to the diagnosis of COVID-19 may explain such a result need to be explored.