Contrary to some popular wisdom — and quite a few ancient one-liners — people who never marry appear destined to die younger than married persons.

These findings are based on national census and death certification data from almost 67,000 adults in the USA between 1989 and 1997.

In 1989, about half of the adults studied were married, and almost one in 10 were widowed. Twelve percent were divorced and 3% were separated. Of the remainder, 5% were cohabiting and one in five had never been married.

The never married longevity "penalty" was larger for those in very good or excellent health and smallest for those in poor health, and it was greater among men than women.

It is no great surprise that old age and poor health were the strongest predictors of death but a stable marriage was also strongly associated with a longer life.

After adjusting for age, health and other factors, those who had been widowed were almost 40% more likely to die between 1989 and 1997. Those who had been divorced or separated were 27% more likely to have do so.

But those who had never been married were an amazing 58% more likely to have died during this period than their married peers.

The never married longevity "penalty" was larger for those in very good or excellent health and smallest for those in poor health, and it was greater among men than women.

Never married men were more vulnerable than their never married female counterparts, and never married men between the ages of 19 and 44 were more than twice as likely to die as their married male peers of the same age.

Although some have speculated that this may reflect the phenomenon of single men engaging in more "risky" behaviors, the authors of the study deny this, pointing out that members of the unmarried group were only slightly more likely to smoke than their married counterparts and they were less likely to drink alcohol regularly. Single people also exercised slightly more and were less overweight.

The authors of the study, which appears in the September 2006 Journal of Epidemiology and Community Health, favor the explanation that marriage is a rough indicator of a person's social connectedness — which many studies have associated with mental and physical health — and that never having married may be a symptom of severe social isolation.