From testing to mortality: COVID-19 and the inverse care law in switzerland

Background: The SARS-CoV-2 pandemic has created unprecedented challenges for society and healthcare systems worldwide. Switzerland is one of the more affected countries in Europe. We examined the association between socioeconomic position (SEP) and SARS-CoV-2 tests, SARS-CoV-2-positive cases, COVID-19 hospitalisations and COVID-19 deaths in Switzerland. Methods: We used surveillance data reported to the Federal Office of Public Health from March to October, 2020. We geocoded patients' residential addresses to determine the Swiss neighbourhood index of SEP, based on education and occupation of household heads, rent per square meter, and crowding. We used negative binomial regression models adjusted for sex, age, canton of residence and wave of the epidemic (first, March to June;second, July to October) to investigate the association between deciles of the SEP index (1st=lowest, 10th=highest) and four outcomes. We used different denominators: the 2018 Swiss population for tests and deaths, the number of tests for positive cases, and the number of positive cases for hospitalisations. Results: Analyses were based on 1,130,405 SARS-CoV-2 tests, 143,101 positive cases, 6,367 hospitalisations and 1,749 deaths up to 31 October 2020. Figure 1 shows the distribution across deciles of neighbourhood SEP of (A) tests per population, (B) positive cases per test, (C) hospitalisations per case and (D) deaths per population (the black lines and shaded areas show the corresponding model prediction adjusted for sex, age, canton of residence and wave of the epidemic -- median posterior and 95% credible interval). The adjusted change in proportion per 1 decile increase in neighbourhood SEP was +2.4% (95% credible interval: 1.0 to 3.9) for tests per population, -2.4% (-3.6 to -1.1) for positive cases per test, -4.6% (-5.9 to -3.3) for hospitalisations per case and -4.5% (-7.7 to -1.4) for deaths per population. Conclusion: This nation-wide study provides a comprehensive analysis of the association between SEP and SARS-CoV-2 testing, reported infections, and COVID-19-related hospitalisations and deaths. People living in neighbourhoods with higher SEP are more likely to be tested, but less likely to test positive, to be hospitalised or to die, a manifestation of the inverse care law where availability of care varies inversely with the need for it.