How to investigate human health effects related to exposure to mixtures of per- and polyfluoroalkyl substances: A systematic review of statistical methods.

BACKGROUND: Humans are exposed to several per- and polyfluoroalkyl substances (PFAS) daily; however, most previous studies have focused on individual PFAS. Although attention to effects of exposure to mixtures of PFAS has grown in recent years, there is no consensus on the appropriate statistical methods that can be used to assess their combined effect on human health. OBJECTIVES: We aim to perform a comprehensive review of the statistical methods used in the existing studies which evaluate the association between exposure to mixtures of PFAS and any adverse human health effect. METHODS: The online databases PubMed, Embase and Scopus were searched for eligible studies, published during the last ten years (last search performed on April 08, 2021). Covidence software was used by two different reviewers to perform a title/abstract screening, followed by a full text revision of the selected papers. RESULTS: A total of 3640 papers were identified, and after the screening process, 53 papers were included in the current review. Most of the studies were published between 2019 and 2021 and were conducted mainly in North America and Europe; more than half of the studies (28 out of 53) were conducted on mother and child pairs. WQS (Weighted Quantile Sum) Regression and BKMR (Bayesian Kernel Machine Regression) were used in 36 out of 53 papers to model mixtures' effects. Health outcomes included in the studies are immunotoxicity (n = 8), fetal development (n = 7), neurodevelopment (n = 9), reproductive hormones (n = 6), thyroid hormones (n = 7), outcomes related to metabolic pathways (n = 16). CONCLUSION: Studies on human exposure to PFAS as complex mixtures and health consequences have substantially increased in the last few years. Based on our findings, we propose that addressing risk from PFAS mixtures will likely require combinations of approaches and implementation of constantly evolving statistical methods. Specific guidelines and tools for quality assessment and publication of mixture observational studies are warranted.

Exposure to Perfluoroalkyl Substances and Mortality for COVID-19: A Spatial Ecological Analysis in the Veneto Region (Italy).

BACKGROUND: In the context of the COVID-19 pandemic, there is interest in assessing if per- and polyfluoroalkyl substances (PFAS) exposures are associated with any increased risk of COVID-19 or its severity, given the evidence of immunosuppression by some PFAS. The objective of this paper is to evaluate at the ecological level if a large area (Red Zone) of the Veneto Region, where residents were exposed for decades to drinking water contaminated by PFAS, showed higher mortality for COVID-19 than the rest of the region. METHODS: We fitted a Bayesian ecological regression model with spatially and not spatially structured random components on COVID-19 mortality at the municipality level (period between 21 February and 15 April 2020). The model included education score, background all-cause mortality (for the years 2015-2019), and an indicator for the Red Zone. The two random components are intended to adjust for potential hidden confounders. RESULTS: The COVID-19 crude mortality rate ratio for the Red Zone was 1.55 (90% Confidence Interval 1.25; 1.92). From the Bayesian ecological regression model adjusted for education level and baseline all-cause mortality, the rate ratio for the Red Zone was 1.60 (90% Credibility Interval 0.94; 2.51). CONCLUSION: In conclusion, we observed a higher mortality risk for COVID-19 in a population heavily exposed to PFAS, which was possibly explained by PFAS immunosuppression, bioaccumulation in lung tissue, or pre-existing disease being related to PFAS.

Survival of Hospitalized COVID-19 Patients in Northern Italy: A Population-Based Cohort Study by the ITA-COVID-19 Network.

INTRODUCTION: COVID-19 case fatality rate in hospitalized patients varies across countries and studies. Reliable estimates, specific for age, sex, and comorbidities, are needed to monitor the epidemic, to compare the outcome in different settings, and to correctly design trials for COVID-19 interventions. The aim of this study was to provide population-based survival curves of hospitalized COVID-19 patients. MATERIALS AND METHODS: A cohort study was conducted in three areas of Northern Italy, heavily affected by SARS-CoV-2 infection (Lombardy and Veneto Regions, and Reggio Emilia province), using a loco-regional COVID-19 surveillance system, linked to hospital discharge databases. We included all patients testing positive for SARS-CoV-2 RNA by RT-PCR on nasopharyngeal/throat swab samples who were hospitalized from 21 February to 21 April 2020. Kaplan-Meier survival estimates were calculated at 14 and 30 days for death in any setting, stratifying by age, sex, and the Charlson Index. RESULTS: Overall, 42,926 hospitalized COVID-19 patients were identified. Patients' median age was 69 years (IQR: 57-79), 62.6% were males, and 6.0% had a Charlson Index ≥3. Survival curves showed that 22.0% (95% CI 21.6-22.4) of patients died within 14 days and 27.6% (95% CI 27.2-28.1) within 30 days from hospitalization. Survival was higher in younger patients and in females. The negative impact of comorbidities on survival was more pronounced in younger age groups. CONCLUSION: The high fatality rate observed in the study (28% at 30 days) suggests that studies should focus on death as primary endpoint during a follow-up of at least one month.

Epidemiology and public health response in early phase of COVID-19 pandemic, Veneto Region, Italy, 21 February to 2 April 2020.

BackgroundVeneto was one of the Italian regions hit hardest by the early phase of the coronavirus disease (COVID-19) pandemic.AimThis paper describes the public health response and epidemiology of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections in the Veneto Region from 21 February to 2 April 2020.MethodsInformation on the public health response was collected from regional health authorities' official sources. Epidemiological data were extracted from a web-based regional surveillance system. The epidemic curve was represented by date of testing. Characteristics of hospitalised COVID-19 cases were described and compared to those never admitted to hospital. Age- and sex-stratified case-fatality ratios (CFRs) were calculated.ResultsKey elements of the regional public health response were thorough case-finding and contact tracing, home care for non-severe cases, creation of dedicated COVID-19 healthcare facilities and activation of sub-intensive care units for non-invasive ventilation. As at 2 April 2020, 91,345 individuals were tested for SARS-CoV-2 and 10,457 (11.4%) were positive. Testing and attack rates were 18.6 per 1,000 and 213.2 per 100,000 population, respectively. The epidemic peaked around 20 to 24 March, with case numbers declining thereafter. Hospitalised cases (n = 3,623; 34.6%) were older and more frequently male compared with never-hospitalised cases. The CFR was 5.6% overall, and was higher among males and people > 60 years of age.ConclusionIn the Veneto Region, the strict social distancing measures imposed by the Italian government were supported by thorough case finding and contact tracing, as well as well-defined roles for different levels of care.