The study's results tally with past research linking religious involvement or spiritual experience to well-being.

Dr. Harold Koenig, a researcher at Duke University Medical Center, said that the study involving patients treated at o­ne hospital over 15 months is unique in that it links religious and spiritual practice to the need for long-term health care.

"This doesn't prove that religion improves health," Koenig told Reuters Health. But he said there does seem to be a connection between belief and health which researchers are seeking to sort out.

In the book, Inglehart and Norris explore the reasons behind the enduring vitality of religion in the modern world. They look at the continued popularity of church-going in the United States and the emergence of New Age spirituality in Western Europe. They study the surge of fundamentalist Islam in the Muslim world, the evangelical revival sweeping through Latin America, and the intractability of widespread ethno-religious conflicts around the world.