Communities across Britain are more fragmented than they have been since records began, with the problem of social isolation worse in parts of Scotland than anywhere else, a study has found.

It also revealed that Glasgow has the highest mortality rate in Britain, and that around one-third of Scots were "breadline poor" with incomes so low they could not live "in the norms of society".

Researchers at Sheffield University analysed the health of local communities, taking into account factors such as the number of unmarried adults, the number of people living alone and the number of residents who had moved into an area within the last year. The results were weighted and used to create an index of "anomie" - a sociological term meaning "a feeling of not belonging".

The research team, which was commissioned by the BBC, found that the Holyrood area of Edinburgh scored highest on this "loneliness scale", with a rating of 86%, while Edinburgh as a whole was the most fragmented community in Britain. The capital has grown 13% more fragmented since 1971, the academics said, overtaking London as the UK's loneliest city.

The study's authors suggested that the high student population in central Edinburgh - a catchment that included Edinburgh University - was a key factor in the community's relatively poor score. They added that the large proportion of homes occupied by young professionals was another reason for the lack of local spirit.

Dr Bethan Thomas, a member of the research team, said: "Isolation and fragmentation is not always intuitive. You get some yuppie bits in towns, with nice looking flats, but the people there might not know each other at all.

"I think in poorer areas people might tend to know their neighbours more, hanging together when there are problems."

Dr Thomas added that the trend away from close community relations could have negative implications for society.

"There's much less community than before, and it seems we are perhaps becoming more selfish," she said. "But then again, that's not necessarily bad - I've had comments from people who said they didn't like their neighbours knowing everything they do, which happens in closer communities."

Steve Cardownie, deputy leader of Edinburgh City Council, found the results surprising.

"I grew up in a tenement community in the city and there still are areas in Edinburgh with a community spirit, but maybe some of these communities have dispersed now as people move into different styles of homes where, for example, they are now not passing people in a stairwell," he said. "I think it also depends on what people's personalities are like, as some people who live on their own may have a very entertaining life and enjoy being on their own."

In Scotland, the most socially inclusive communities included East Dunbartonshire's Milngavie, which scored 16.4%, and Giffnock, in East Renfrewshire, with 16.79%.

Scotland had the UK's highest proportion of poor residents in every decade the study looked at, with the figure rising from 27% to 32% during the 1990s.

SNP work and pensions spokesman, John Mason MP, said: "These findings are nothing short of shameful, and show an absolute failure by Labour to tackle poverty. Under Labour we have seen the rich get richer and the poor get poorer."

The high mortality rate, which means that a Glasgow resident is 31% more likely to die on any given day than an average UK resident, was attributed to lifestyle factors.

Dr Thomas said: "The mortality rate is nothing new, and it's down to diet, alcohol diseases and smoking-related diseases. It's too soon to see the impact of things like the smoking ban, or the improved health and care."