A girl born in Japan today will probably live to celebrate her 86th birthday, the longest life expectancy anywhere in the world, according to the World Health Organisation, which announced its annual health statistics today.

Men live longest in San Marino, where the average life expectancy for a boy born today is 81.

Sierra Leone has the shortest life expectancy for men, just 39, while Afghan men live to 41 and women to 42 on average.

The figures for 2007, the latest year available, show a sharp decline in life expectancy in many African countries since 1990, largely due to the HIV pandemic.

The southern African nation of Lesotho recorded a fall of 16 years for men and women, to 43 and 47 respectively. In the nearby kingdom of Swaziland, women now live to 49 on average, a fall of 14 years, while men's life expectancy had declined by 12 years to 47.

Botswana, Congo, Kenya, South Africa and Zambia also reported significant drops in life expectancy for both sexes since 1990.

In Zimbabwe, where the economic crisis has created shortages of food and medicine, women's life expectancy fell by 19 years to 44, and men's by 12 years to 45.

The data also showed that some countries have made remarkable progress in increasing life expectancy since 1990 – partly by ending wars, partly through successful health initiatives.

Eritrea's life expectancy during that period rose by 33 years to 61 for men, and by 12 years to 65 for women. In Liberia, the figure for men jumped by 29 years to 54, and by 13 years to 58 for women. Angola, Bangladesh, Maldives, Niger and East Timor also increased average life expectancies for men and women by 10 years.

In the US, the life expectancy was on the rise for both sexes: up to 76 from 72 for men, and to 81 from 79 for women.

In Russia, the average life expectancy for men has dropped to 60 from 64 since the Soviet era. For women it fell to 73 from 74.