Globally, people's health is improving and life expectancy is rising, but progress is far from universal with chronic diseases bringing long-term illness and causing seven out of 10 deaths, according to research published on Thursday. The Global Burden of Disease study, which shows the key drivers of ill health, disability and death in individual countries, found that by 2015, the world population had gained more than a decade of life expectancy since 1980 - rising to 69.0 years in men and 74.8 years in women.

Among main contributors to this were large falls in death rates for many communicable or infectious diseases, including HIV/AIDS, malaria and diarrhea. The rate of people dying from cardiovascular disease and cancers has also fallen, the study found, although at a slower pace.

The study analyzed 249 causes of death, 315 diseases and injuries and 79 risk factors in 195 countries and territories between 1990 and 2015. Christopher Murray, director of the Institute for Health Metrics and Evaluation at the University of Washington, which led the study, said its results painted a picture of patchy health gains across the world, driven in part by economic development.

"Development drives, but does not determine health," he said in a statement as the findings were published in The Lancet medical journal. "We see countries that have improved far faster than can be explained by income, education or fertility. And we also continue to see countries - including the United States - that are far less healthy than they should be given their resources."

As well as life expectancy, the study estimated healthy life expectancy - the number of years people can expect to live in good health. It found that while healthy life expectancy had increased in 191 of 195 countries - by 6.1 years - between 1990 and 2015, it had not risen as much as overall life expectancy, meaning people are living more years with illness and disability. Among the world's wealthier regions, North America had the worst healthy life expectancy at birth for both men and women.