Washington ? The global mortality rate for adults has fallen by about 1 percent a year for the past 40 years, with women making greater gains than men and huge differences opening up between countries and regions over that period, according to a new study.

The AIDS epidemic, the collapse of the Soviet Union and smoking appear to be the main forces driving global changes in adult mortality over those decades. AIDS and post-Soviet social upheaval combined to make the early 1990s a deadly bump in an otherwise steady downward trend line.

As a consequence, men in much of Africa and the former Soviet Union have higher risks of dying between the ages of 15 and 60 than they had in 1970. At the same time, mortality rates among Asian women have fallen. Indian women in 1970 had higher mortality than men; that is no longer the case. South Korean women today are second only to Cypriot women in having the lowest adult mortality. In 1970, they were No. 123 in the ranking.

The analysis, published online Friday in the journal Lancet, is the most detailed study to date of nation-by-nation trends in adult mortality.

Child mortality — deaths before the 5th birthday — and maternal mortality are the main focus of global mortality studies. That’s because those demographic groups are the target of many interventions and their mortality was thought to be a gauge of an entire population’s health.

The new analysis, however, suggests that’s not true now.

“It’s no longer the case that what’s happening to kids is what’s happening to adults,” said Christopher J.L. Murray, the University of Washington physician and epidemiologist who led the study. “In many places, child mortality is getting better and adult mortality is getting worse.”

Murray and his colleagues looked at nearly 4,000 measurements of adult mortality for 187 countries, including census records, vital statistics data and population surveys.

Adult mortality, measured as the probability of dying after the 15th birthday but before the 60th, dropped 19 percent for men and 34 percent for women over the past 40 years.

The country with the lowest adult male mortality was Iceland, with 65 premature deaths per 1,000 men. The highest was Swaziland, with 765 premature deaths per 1,000 men. For women, the country with the lowest rate was Cyprus (38 deaths per 1,000) and the highest Zambia (606 deaths per 1,000).

The rate for U.S. men was 130, which ranked 45th in the world. For U.S. women it was 77, ranking 49th. The average decline over the four decades was less than 1 percent a year.