Sociodemographic and regional differences in neonatal and infant mortality in Switzerland: The Swiss National Cohort

Background Despite a well-funded healthcare system with universal insurance coverage, Switzerland has one of the highest neonatal and infant mortality rates among high-income countries. Identifying avoidable risk factors targeted by evidence-based policies is a public health priority. We describe neonatal and infant mortality in Switzerland from 2011–2018 and explore associations with neonatal and pregnancy-related variables, parental sociodemographic information, regional factors, and socioeconomic position (SEP) using data from a long-term nation-wide cohort study. Methods We included 680,077 live births—representing 99.3% of all infants born in Switzerland between January 2011 and December 2018. We deterministically linked the national live birth register with the mortality register and with census and survey data to create a longitudinal dataset of neonatal and pregnancy-related variables; parental sociodemographic information, such as civil status, age, religion, education, nationality; regional factors, such as urbanity, language region; and the Swiss neighbourhood index of SEP (Swiss-SEP index). Information on maternal education was available for a random subset of 242,949 infants. We investigated associations with neonatal and infant mortality by fitting multivariable Poisson regression models with robust standard errors. Several sensitivity analyses assessed the robustness of our findings. Results Overall, neonatal mortality rates between 2011 and 2018 were 3.0 per 1000 live births, varying regionally from 3.2 in German-speaking to 2.4 in French-speaking and 2.1 in Italian-speaking Switzerland. For infant mortality, respective rates were 3.7 per 1000 live births overall, varying from 3.9 to 3.3 and 2.9. Adjusting for sex, maternal age, multiple birth and birth rank, neonatal mortality remained significantly associated with language region [rate ratio (RR) 0.72, 95% confidence interval (CI): 0.64–0.80 for French-speaking and RR 0.66, 95% CI: 0.51–0.87 for Italian-speaking region], with marital status (RR 1.55, 95% CI: 1.40–1.71 for unmarried), nationality (RR 1.40, 95% CI: 1.21–1.62 for non-European Economic Area vs. Swiss), and the Swiss-SEP index (RR 1.17, 95% CI: 1.00–1.36 for lowest vs. highest SEP quintile). In the subset, we showed a possible association of neonatal mortality with maternal education (RR 1.24, 95% CI: 0.95–1.61 for compulsory vs tertiary education). Conclusion We provide detailed evidence about the social patterning of neonatal and infant mortality in Switzerland and reveal important regional differences with about 30% lower risks in French-and Italian-speaking compared with German-speaking regions. Underlying causes for such regional differences, such as cultural, lifestyle, or healthcare-related factors, warrant further exploration to inform and provide an evidence base for public health policies. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement The Swiss National Cohort is funded by the Swiss National Science Foundation (SNSF) cohort grant No. 148415. Our current analysis was funded by SNSF project grant No. 163452. ME was supported by special SNSF project funding (grant No. 174281). LDS was funded by an SNSF grant to CEK (SNSF 320030B_192804/1). ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The Swiss National Cohort has been approved by the Ethics Committee of the Canton of Bern (Switzerland). I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data are available upon reasonable request. Data may be obtained from a third party and are not publicly available.