People who lived their whole lives in poverty are likely to die younger, on average, than those who lived more comfortably, according to a study of more than 6,000 people in more than a dozen countries.
They also are more likely to be in a higher level of poverty and to die earlier than people who live longer.
The finding by researchers at the University of California, Berkeley, is the first to suggest that living in poverty increases mortality risk.
For most people, life expectancy is lower when they live in poverty.
The study, published online Tuesday in the journal Science, found that the average life expectancy in countries where poverty is higher is about 12 years less than the average in the countries with the lowest poverty levels.
Life expectancy was lower in places with lower levels of inequality.
For example, the life expectancy of people in the United States with incomes above $70,000 was about 17 years less in China, the study found.
Life-expectancy gains over time in a number of areas are a good indicator of health, said Robert W. Campbell, the lead author of the study and a professor of epidemiology at UC Berkeley.
“We can see that people living in poor households tend to have lower life expectancies, and that the effect of income inequality is not linear with the level of inequality,” he said.
The researchers found that life expectancy gains in poor countries with high levels of income equality were not as strong as those in other countries with lower inequality.
“The findings suggest that income inequality increases the risk of premature death in low-income countries,” Campbell said.
But, he added, “the evidence that inequality increases mortality is limited and there are several limitations of this study.”
The researchers looked at life expectancy and mortality from age-adjusted data from the World Health Organization, the United Nations Population Division, the World Bank, the Institute of Medicine and the National Center for Health Statistics.
In the U.S., life expectancy at birth was about 79.4 years in 2014, compared with 77.5 years in China and 73.7 years in Japan, according the WHO.
The average life span of people living below the poverty line in the U