Most countries around the world have seen a significant improvement in life expectancy over the past two decades. Scientists have analyzed what factors have influenced this in the past and made a forecast of future trends, writes Ars Technica.

The study is entitled “Convergence and divergence in mortality: A global study from 1990 to 2030” (Convergence and divergence in mortality: A global study from 1990 to 2030). It was published in the scientific journal PLOS One.

The research team used specific mortality rates to identify global groups that reflect average life expectancy in different parts of the world. Countries in these groups changed from 1990 to 2010 and are projected to change even more by 2030.

Groups comprising predominantly richer countries had the best chances of longevity in 1990 and 2010. In contrast, low-income countries had the worst mortality rates. In 1990, these countries, many of which are in Africa, suffered from war, political upheaval, and HIV/AIDS.

Along with the weak healthcare system, the factors that led to the high mortality rate in most African countries remained as problematic in 2010.

In all groups, the life expectancy of men living in a particular group country tended to differ less than that of women. But in some regions, there were differences between the life expectancy of men and women.

For example, after the collapse of the Soviet Union in the 1990s, mortality among the male population of the former Soviet republics increased significantly, and this trend continued in 2010.

The causes of death in these countries were violence, accidents, cardiovascular disease, alcohol, inadequate health care, poverty, and psychosocial stress.

Experts advise taking forecasts for 2030 with a grain of salt. Although past trends can be good indicators of what will happen in the future, they do not always hold true.

But if past and current trends continue for the foreseeable future, some countries may be worse off in 2030. The group of countries with the lowest income and highest mortality rates will include several African countries that have been severely affected by wars, political and socioeconomic challenges.

The second group of low-income, high-mortality countries, also predominantly African, will now be joined by some countries in Eastern Europe and Asia. These are countries that suffer from political and socioeconomic problems, most of which have recently been involved in conflicts and wars or are still in them, such as Ukraine.

Some countries, such as Chile, will join the group of countries with the highest incomes and lowest mortality rates. The former Soviet countries are likely to continue to face the same challenges as in 1990 and 2010. They will fall into one of the groups with average income and average life expectancy.

The study places the United States in the first or second group of countries with high income and low mortality. This may give the impression that things are going well on a global scale. Although the study does not look specifically at the United States, there are some local issues that suggest otherwise.

For example, life expectancy in the United States continues to fall rapidly. Cancer, heart disease, strokes, drug overdoses, and accidents are the culprits behind this trend, especially among middle-aged Americans.