Impact of the COVID-19 epidemic in Friuli Venezia Giulia Region (Northern Italy): assessment of factors associated with the risk of death by competing risks analysis

OBJECTIVES: to investigate the role of gender, age, province of residence, and nursing home residency on the risk of death for residents in the Friuli Venezia Giulia (FVG) Region (Northern Italy) tested positive for Covid-19, considering recovery as a competing event. The secondary objective is to describe the impact of the Covid-19 epidemic in FVG and in the Regions of Northern and Central Italy in terms of incidence and mortality compared to the national data. DESIGN: retrospective cohort study. SETTING AND PARTICIPANTS: resident population in FVG in the period between 29 February and 25 June 2020. MAIN OUTCOME MEASURES: in order to describe the impact of the Covid-19 outbreak in FVG, in terms of incidence and mortality compared to the national data, the standardized incidence (SIR) and mortality (SMR) ratios and their respective 95% confidence intervals (95%CI) were calculated compared to the Italian population for the northern and central Regions of Italy and the autonomous Provinces (PA) of Trento and Bolzano. A retrospective cohort study was conducted on subjects residing in FVG to whom at least one naso-oropharyngeal swab (hereafter, named swab) resulted positive for Covid-19. For each subject included in the cohort, the observation period started with the first positive swab and ended with the first of the following events: death, recovery or censored, which means that at the end of the observation period the subject was still alive and positive. The cause of death was assigned to Covid-19 if a subject had not yet recovered at the time when the event occurred. Cohort members were considered recovered after two negative consecutive swabs. The sub-hazard ratio (SHR) was estimated by applying the regression model of competing risks by Fine and Gray, in which the event of interest was the death caused by Covid-19 and the competing event was recovery. The explanatory variables included in the multiple models are: gender, age at the beginning of the observation period, the Province of residence, and nursing home residency. The cause-specific hazard was estimated using Cox proportional hazard regression. RESULTS: during the observation period, 3,305 cases and 345 deaths were recorded in FVG; SIR and SMR resulted, respectively, equal to 0.64 (95%CI 0.61-0.68) and 0.43 (95%CI 0.37-0.50). The FVG was the Northern Region one with the lowest incidence and mortality. The cohort consisted of 3,121 residents in FVG with at least one swab with a positive Covid-19 result during the study period. The SHR of dying for Covid-19 is equal to 16.13 (95%CI 9.73-26.74) for people with age 70-79 years and 35.58 (95%CI 21.77-58.15) with age >=80 years respect those with age <70 years. It is higher in males (SHR 1.71; 95%CI 1.34-2.17). There is no evidence that being resident in a nursing home affects the SHR (SHR 0.91 and 95%CI 0.69-1.20). As regards the province as an explanatory variable, the sub-hazard of death in the province of Trieste appears to overlap to the sub-hazard of Pordenone used as a reference; for the provinces of Udine and Gorizia the sub-hazards seem lower than the reference. CONCLUSIONS: while other Northern Regions and autonomous Provinces show higher standardized incidence and mortality compared with Italy, FVG and Veneto do not. In FVG, male gender and age are important determinants of death while there is no evidence that the condition of guest in a nursing home increases the sub-hazard of death.