People who follow a healthy lifestyle live up to 6 years longer compared with those with a high risk profile, reveals a Swedish study.

Living a healthy lifestyle into old age add five years to women's lives and six years to men's, the study found.

This is the first study that directly provides information about differences in longevity according to several modifiable factors, said researchers.

It is well known that lifestyle factors, like being overweight, smoking and heavy drinking, predict death among elderly people. But is it uncertain whether these associations are applicable to people aged 75 years or more.

So a team of researchers based in Sweden measured the differences in survival among adults aged 75 and older based on modifiable factors such as lifestyle behaviours, leisure activities, and social networks.

The study involved just over 1,800 individuals who were followed for 18 years (1987-2005). Data on age, sex, occupation, education, lifestyle behaviours, social network and leisure activities were recorded.

During the follow-up period 92 percent of participants died. Half of the participants lived longer than 90 years.

Survivors were more likely to be women, be highly educated, have healthy lifestyle behaviours, have a better social network, and participate in more leisure activities than non-survivors.

The results showed that smokers died one year earlier than non-smokers. Former smokers had a similar pattern of survival to never smokers, suggesting that quitting smoking in middle age reduces the effect on mortality.

Of the leisure activities, physical activity was most strongly associated with survival. The average age at death of participants who regularly swam, walked or did gymnastics was two years greater than those who did not.

Overall, the average survival of people with a low risk profile (healthy lifestyle behaviours, participation in at least one leisure activity, and a rich or moderate social network) was 5.4 years longer than those with a high risk profile (unhealthy lifestyle behaviours, no participation in leisure activities, and a limited or poor social network).

Even among those aged 85 years or older and people with chronic conditions, the average age at death was four years higher for those with a low risk profile compared with those with a high risk profile.

In summary, the associations between leisure activity, not smoking, and increased survival still existed in those aged 75 years or more, with women's lives prolonged by five years and men's by six years, the researchers said.

These associations, although attenuated, were still present among people aged 85 or more and in those with chronic conditions, they added.

"Our results suggest that encouraging favourable lifestyle behaviours even at advanced ages may enhance life expectancy, probably by reducing morbidity," they concluded.

The results have been published on bmj.com.