Impact of the COVID-19 pandemic on breast cancer screening indicators in a Spanish population-based program: a cohort study (preprint)

BackgroundTo assess the effect of the COVID-19 pandemic on performance indicators in the population-based breast cancer screening program of Parc de Salut Mar (PSMAR), Barcelona, Spain. MethodsWe conducted a before-and-after, quasi-experimental study to evaluate participation, recall, false-positives, cancer detection rate, and cancer characteristics in our screening population from March 2020 to March 2021 compared with the four previous rounds (2012-2019). Using independent logistic regression models, we estimated the adjusted odds ratios (aOR) of each of the performance indicators for the COVID-19 period, controlling by type of screening (prevalent or incident), socioeconomic index, family history of breast cancer, and menopausal status. We analyzed 144,779 observations from 47,571 women. ResultsDuring the COVID-19 period, the odds of participation were 11% lower in first-time invitees (aOR=0.89[95%CI=0.84-0.96]) and in those who had previously participated regularly and irregularly (aOR=0.65 [95%CI=0.61-0.69] and aOR=0.93 [95%CI=0.85-1.03], respectively). Participation showed a modest increase in women not attending any of the previous rounds (aOR=1.07 [95%CI=0.99-1.17]). The recall rate slightly decreased in both prevalent and incident screening (aOR=0.89 [95%CI=0.78-1.01] and aOR=0.89 [95%CI=0.79-1.00], respectively). No significant differences were observed in false-positives (prevalent - aOR=1.07 [95%CI=0.92-1.24] and incident screening -aOR=0.94 [95%CI=0.82-1.08]), cancer detection rate (aOR=0.91 [95%CI=0.69-1.18]), or cancer stages. ConclusionsThe COVID-19 pandemic negatively affected screening attendance, especially in previous participants and newcomers. We found no marked differences in recall, false-positives, or cancer detection, indicating the programs resilience. There is a need for further evaluations of interval cancers and potential diagnostic delays.

Effects of environmental factors on severity and mortality of COVID-19 (preprint)

BackgroundMost respiratory viruses show pronounced seasonality, but for SARS-CoV-2 this still needs to be documented. MethodsWe examined the disease progression of COVID-19 in 6,914 patients admitted to hospitals in Europe and China. In addition, we evaluated progress of disease symptoms in 37,187 individuals reporting symptoms into the COVID Symptom Study application. FindingsMeta-analysis of the mortality risk in eight European hospitals estimated odds ratios per one day increase in the admission date to be 0.981 (0.973-0.988, p<0.001) and per increase in ambient temperature of one degree Celsius to be 0.854 (0.773-0.944, p=0.007). Statistically significant decreases of comparable magnitude in median hospital stay, probability of transfer to Intensive Care Unit and need for mechanical ventilation were also observed in most, but not all hospitals. The analysis of individually reported symptoms of 37,187 individuals in the UK also showed the decrease in symptom duration and disease severity with time. InterpretationSeverity of COVID-19 in Europe decreased significantly between March and May and the seasonality of COVID-19 is the most likely explanation. Mucosal barrier and mucociliary clearance can significantly decrease viral load and disease progression, and their inactivation by low relative humidity of indoor air might significantly contribute to severity of the disease.