Challenges in assessing area-level mortality inequalities

Lower life expectancy in more deprived regions has been a frequent and consistent observation and is indicative of public health challenges. Germany is no exception. In The Lancet Public Health, Fabian Tetzlaff and colleagues1Tetzlaff F Sauerberg M Grigoriev P et al.Age-specific and cause-specific mortality contributions to the socioeconomic gap in life expectancy in Germany, 2003–21: an ecological study.Lancet Public Health. 2024; 9: e295-e305Summary Full Text Full Text PDF Google Scholar report their ecological study in which they found that inequalities in mortality across German regions, grouped into area-level deprivation quintiles, have been increasing since the mid-2000s. This development comes after decreasing regional mortality inequalities were found in the 1990s, brought about by German reunification.2van Raalte AA Klüsener S Oksuzyan A Grigoriev P Declining regional disparities in mortality in the context of persisting large inequalities in economic conditions: the case of Germany.Int J Epidemiol. 2020; 49: 486-496Crossref Google Scholar Tetzlaff and colleagues investigated the causes of death that contributed to the increasing gap in life expectancy between areas with high and low deprivation using rigorous life table decomposition methods. Next to differences in cardiovascular mortality, which have long been dominant in explaining regional mortality patterns, this new study highlights that cancer mortality in middle-to-old age (40–74 years) increasingly explains the life-expectancy gap between the least and most deprived areas. Most of the excess cancer mortality in more deprived areas was found to be due to preventable or treatable cancers, and, importantly, lung cancer. As such, this study strengthens the evidence base on area-level socioeconomic mortality inequalities. A key open question is how to interpret the magnitude of these inequalities. By international standards, the life-expectancy gap of 1·8 years for female individuals and 3·1 years for male individuals between the least and most deprived area-level quintiles in 2019 in Germany appears small.3Ezzati M Friedman AB Kulkarni SC Murray CJL The reversal of fortunes: trends in county mortality and cross-county mortality disparities in the United States.PLoS Med. 2008; 5: e66Crossref PubMed Scopus (271) Google Scholar, 4Seaman R Riffe T Leyland AH Popham F van Raalte A The increasing lifespan variation gradient by area-level deprivation: a decomposition analysis of Scotland 1981–2011.Soc Sci Med. 2019; 230: 147-157Crossref PubMed Scopus (0) Google Scholar, 5Singh GK Siahpush M Widening socioeconomic inequalities in US life expectancy, 1980-2000.Int J Epidemiol. 2006; 35: 969-979Crossref PubMed Scopus (291) Google Scholar, 6Tobias MI Cheung J Monitoring health inequalities: life expectancy and small area deprivation in New Zealand.Popul Health Metr. 2003; 1: 2Crossref PubMed Scopus (0) Google Scholar Low area-level socioeconomic inequalities by international standards could come about for several reasons. First, socioeconomic inequalities in mortality could be comparatively low; however, the studies of individual-level mortality inequalities by socioeconomic status cited by Tetzlaff and colleagues in their Article1Tetzlaff F Sauerberg M Grigoriev P et al.Age-specific and cause-specific mortality contributions to the socioeconomic gap in life expectancy in Germany, 2003–21: an ecological study.Lancet Public Health. 2024; 9: e295-e305Summary Full Text Full Text PDF Google Scholar suggest that this is not the case. But, as they point out, the evidence base for Germany is weak because there is no mortality follow-up to the census and existing surveys are underpowered or unrepresentative. Second, area-level mortality inequalities might be comparatively low, which might indeed be the case for Germany. Studies of differences in life expectancy in Germany at the state level2van Raalte AA Klüsener S Oksuzyan A Grigoriev P Declining regional disparities in mortality in the context of persisting large inequalities in economic conditions: the case of Germany.Int J Epidemiol. 2020; 49: 486-496Crossref Google Scholar and at Nomenclature of Territorial Units for Statistics level 3 (NUTS-3)7Rau R Schmertmann CP District-level life expectancy in Germany.Dtsch Arztebl Int. 2020; 117: 493-499Google Scholar have found comparatively small differences in mortality between regions and no outstanding regions with very high life expectancy. Third, granularity of international studies and different definitions of deprivation impede direct comparison. Region sizes in Germany vary, with the most deprived quintile of Germany's 400 NUTS-3 districts potentially not being as deprived as the most deprived quintile of German neighbourhoods. This variation in region sizes contrasts with studies from the UK and USA, which have aggregated populations into smaller and potentially more homogenous areal groups.3Ezzati M Friedman AB Kulkarni SC Murray CJL The reversal of fortunes: trends in county mortality and cross-county mortality disparities in the United States.PLoS Med. 2008; 5: e66Crossref PubMed Scopus (271) Google Scholar, 4Seaman R Riffe T Leyland AH Popham F van Raalte A The increasing lifespan variation gradient by area-level deprivation: a decomposition analysis of Scotland 1981–2011.Soc Sci Med. 2019; 230: 147-157Crossref PubMed Scopus (0) Google Scholar, 5Singh GK Siahpush M Widening socioeconomic inequalities in US life expectancy, 1980-2000.Int J Epidemiol. 2006; 35: 969-979Crossref PubMed Scopus (291) Google Scholar Furthermore, percentile groupings differ across studies, which can affect the size of observed effects, with deciles, quintiles, and tertiles all commonly used. Finally, deprivation indices are defined differently across countries and studies in terms of what factors and age groups they include so that different aspects of deprivation can be captured by them.5Singh GK Siahpush M Widening socioeconomic inequalities in US life expectancy, 1980-2000.Int J Epidemiol. 2006; 35: 969-979Crossref PubMed Scopus (291) Google Scholar Although it is unclear whether Germany has high or low area-level inequalities by international standards, Tetzlaff and colleagues observed a clear within-country trend towards increasing inequalities. The authors showed that these inequalities in life expectancy are driven by the life expectancy in the most deprived areas. The reason for this finding needs to be better understood. The districts included in each deprivation quintile differed from year to year, making it difficult to pinpoint the exact areas of need. Extending the analyses and investigating whether changes in deprivation are regionally patterned and associated with changes in cause-specific mortality will be important for future studies. Tetzlaff and colleagues did not investigate the role of migration in their analyses. The role of migration continues to be an under-researched field in area-level mortality inequality analysis. Migration is usually selective and can intensify area-based inequalities.3Ezzati M Friedman AB Kulkarni SC Murray CJL The reversal of fortunes: trends in county mortality and cross-county mortality disparities in the United States.PLoS Med. 2008; 5: e66Crossref PubMed Scopus (271) Google Scholar, 8Connolly S O'Reilly D Rosato M Increasing inequalities in health: is it an artefact caused by the selective movement of people?.Soc Sci Med. 2007; 64: 2008-2015Crossref PubMed Scopus (64) Google Scholar Ongoing pressures on the affordable housing market might exacerbate the role of selective migration in the future. Additionally, a quasi-experimental approach has shown that people who were quasi-randomly assigned to more deprived regions as part of a settlement scheme had increased mortality rates, supporting the idea that environment affects mortality.9Reiss K Berger U Winkler V Voigtländer S Becher H Razum O Assessing the effect of regional deprivation on mortality avoiding compositional bias: a natural experiment.J Epidemiol Community Health. 2013; 67: 213-218Crossref PubMed Scopus (0) Google Scholar In summary, area-level deprivation captures important inequalities in life expectancy, even if the extremes of area-based deprivation are not captured. The study design of Tetzlaff and colleagues is especially important in Germany, where individual-level mortality inequalities are hard to study.1Tetzlaff F Sauerberg M Grigoriev P et al.Age-specific and cause-specific mortality contributions to the socioeconomic gap in life expectancy in Germany, 2003–21: an ecological study.Lancet Public Health. 2024; 9: e295-e305Summary Full Text Full Text PDF Google Scholar Future work should aim to disentangle the respective roles of changing incidence from changing survival after diagnosis. To pursue prevention, complementary and more refined area classifications might be needed to define preventive measures at different levels. Looking at mortality inequalities from different perspectives and including migration in future studies would be of great benefit, and changes in survival should be monitored alongside changes in deprivation. We declare no competing interests. AvR is supported by an ERC Starting Grant extension by the Max Planck Society. During the preparation of this work the authors used DeepL Write in order to improve readability. After using this tool, the authors reviewed and edited the content as needed and take full responsibility for the content of the publication. Age-specific and cause-specific mortality contributions to the socioeconomic gap in life expectancy in Germany, 2003–21: an ecological studyTo reduce the socioeconomic gap in life expectancy, effective efforts are needed to prevent early deaths from cardiovascular disease and cancer in socioeconomically deprived populations, with cancer prevention and control becoming an increasingly important field of action in this respect. Full-Text PDF Open Access