Geographical and socio-economic inequalities in years of life lost across Norwegian municipalities and city districts in 2019: an ecological registry-based study

Understanding local level impact of socio-economic and spatial disparities on health outcomes is crucial for informing effective public health interventions. This study examines the association between socio-economic factors, centrality, and premature mortality-measured as years of life lost (YLLs)-across Norwegian municipalities. We conducted an ecological, cross-sectional registry-based study across municipalities and districts, each with populations exceeding 1000 as of 1 January 2019. Data on mortality, demographics, education, income, and centrality were sourced from Statistics Norway. All-cause YLLs were calculated by multiplying age-specific mortality numbers by aspirational life expectancy from the Global Burden of Disease 2019 life tables. Municipalities were divided into quartiles based on a composite socio-economic position (SEP) score that integrated education and income, and grouped into centrality categories. Mixed-effects negative binomial regression models, crude and adjusted for age categories and sex, evaluated both relative and absolute associations. The lowest SEP quartile, assessed with a composite SEP score, had a 15% higher YLL rate compared to the highest quartile [incidence rate ratio (IRR) = 1.15; 95% confidence interval (CI) = 1.07-1.24], amounting to an absolute difference of 2127 YLLs per 100 000 population. Similarly, the least central quartile exhibited a 15% higher YLL rate compared to the most central one (IRR = 1.15; 95% CI = 1.09-1.21), translating to an absolute difference of 2057 YLLs per 100 000 population. There are substantial inequalities in premature mortality across Norwegian municipalities, strongly linked to municipal SEP and centrality.