While it was unsurprising that death rates were higher among the homeless the extent of the difference was "startling", and a cause for "grave concern", researchers from the University of Bristol said.
Dr Mary Shaw and Danny Dorling used data from the homeless charity Crisis to calculate mortality rates for rough sleepers in London. It is the first time this has been done with United Kingdom figures.
The data showed that young men aged 16 to 29 had a death risk 40 times the national average. For men aged 16 to 64 years, the risk was estimated to be 25 times greater. An earlier study of street youth in Montreal showed they had almost 12 times more chance of dying than the average Canadian.