Slowdown in Mortality Improvement in the Past Decade: A US/UK Comparison.

OBJECTIVES: To investigate the slowdown in mortality improvement in the United States, United Kingdom, and comparator countries observed in the first decade of the twenty-first century and critically evaluate proposed explanations. METHODS: Change-point analysis to identify the year of change in comparison of national mortality trends and linear spline models in the investigation of subnational differences using data from the Human Mortality Database, Global Burden of Disease cause-specific data, and, for the United Kingdom, national statistics data. Consideration of the impact of using different methods to estimate overall mortality is also concluded together with a review of methodological assumptions made in previous studies. RESULTS: The results confirm the slowdown in mortality improvement observed in the early twenty-first century but indicate that proposed explanations for this are inadequate on a range of counts. DISCUSSION: Mortality improvement slowed down in the early twenty-first century but the explanations advanced, such as opioid use in the United States or influenza epidemics and austerity programs in the United Kingdom, seem unlikely to account for this. Further research considering longer-term life course and cohort influences is needed.