This paper reports on trends in life expectancy in the 28 EU countries and some other high-income OECD countries, and examines potential explanations for the slowdown in improvements in recent years. The slowdown in improvements in life expectancy since 2011 has been greatest in the USA, where life expectancy has fallen in recent years, and the UK, but France, Germany, Sweden and Netherlands have also seen a sharp slowdown. Overall, the pace of mortality improvement has slowed in several EU countries and Australia and Canada since 2011. Diseases of older ages are major contributors to the slowdown. Improvements in cardiovascular (CVD) disease mortality have slowed in many countries, respiratory diseases, including influenza and pneumonia, have claimed excess lives in some winters, and deaths from dementia and Alzheimer's disease are rising. In some countries, notably the USA and the UK, mortality improvements have also slowed or even reversed among working age adults because of the rising numbers dying from drug-related accidental poisoning. The report also considers wider contributing factors. Although some risk factors, such as smoking, excessive alcohol consumption, high blood pressure and cholesterol levels, continue to decline in most EU countries, the prevalence of obesity and diabetes continues to rise. Adverse trends in inequalities could also have an impact if some population groups experience lower gains in longevity than others, thereby reducing the overall gain. Looking ahead, it is unclear whether the current slowdown in mortality improvements in some EU countries and the USA is a long-term trend or not, whether the slowdown in major killers such as CVD will persist, and whether or not the excess winter mortality seen in some years becomes a regular feature given population ageing and increasing numbers of frail, older people. The timely monitoring and investigation of mortality trends, including through international collaboration where possible, can facilitate early implementation of remedial strategies.