People around the world continue to live longer, and in some poor countries the gains have been dramatic, the World Health Organization says in an annual report released last week.

The average girl born in 2012 can expect to reach 73, and the average boy can expect to reach 68. That gives them an average of six years more than children born in 1990, WHO says.

The United States does better than average, with a female life expectancy of 81 and male life expectancy of 76 – but ranks 37th overall and does not make the top 10 for either gender. Top honors go to Japan for women (87 years) and Iceland for men (81.2 years).

The best-improved countries include several that have made double-digit gains since 1990. Those include Liberia, which saw a 20-year increase (from 42 to 62); Ethiopia (45 to 64), Maldives (58 to 77), Cambodia (54 to 72), Timor-Leste, also known as East Timor (50 to 66) and Rwanda (48 to 65).

WHO says several factors are at work:

In poor countries, fewer children are dying before age 5, thanks to advances against premature birth, birth complications and childhood infections.

In rich countries, fewer people are dying of heart disease and stroke before reaching 60, thanks to blood pressure control and other preventive efforts.

In many countries, declining tobacco use is extending lives.

The news is not all good. Life expectancy remains below 55 years in nine countries, all in sub-Saharan Africa: Angola, Central African Republic, Chad, Côte d’Ivoire, Democratic Republic of the Congo, Lesotho, Mozambique, Nigeria and Sierra Leone.

Also, the gap between rich and poor countries remains large: A boy born in a rich country can expect to live to 76, which is 16 years longer than a boy born in a poor country. For girls, the gap is 19 years: 82 vs. 63.

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