http://articles.latimes.com/2009/may/22/world/fg-life-expectancy22United States lags at 78, while in many nations in sub-Saharan Africa, the average life expectancy is in the 40s.May 22, 2009Japan tops world life expectancies with 83 yearsGirls born in Japan today are likely to live until 2095, some with a good chance of seeing the dawn of the next century thanks to having the world's longest life expectancy, the World Health Organization reported from Geneva on Thursday.The tiny nation of San Marino boasts the longest average life span for men,at 81 years. The United States lags behind the top nations, with an average life expectancy of 78 for the two sexes combined.Men in Sierra Leone fare the worst worldwide, living on average just 39 years.Here are the nations at the top and bottom of the list of life expectancies for the two sexes combined as of 2007, according to WHO:Longest life expectanciesAdvertisementJapan: 83Australia: 82Iceland: 82Italy: 82San Marino: 82Switzerland: 82Andorra: 81Canada: 81France: 81Israel: 81Monaco: 81New Zealand: 81Norway: 81Singapore: 81Spain: 81Sweden: 81Shortest life expectanciesSierra Leone: 41Afghanistan: 42Zimbabwe: 45Lesotho: 45Zambia: 46Chad: 46Uganda: 48Swaziland: 48Mozambique: 48Guinea-Bissau: 48Central African Republic: 48Source: World Health Organization