Exercising at least once a month as well as having satisfying relationships in adulthood are linked to better cognitive functioning and good brain health in old age, stopping dementia in its tracks, two studies have suggested.

The exercise study, published in the Journal of Neurology, Neurosurgery, and Psychiatry, showed that people who reported being physically active at least one to four times a month between the ages of 36 and 69 had the biggest cognitive effect.

This effect was greater than for those who reported exercising frequently (more than five times a month) during at least one survey period, but who did not necessarily keep this up, the findings showed.

"Our study suggests that engaging in any leisure-time physical activity, at any point in adult life, has a positive effect on cognition. This seems to be the case even at light levels of activity, between one to four times a month," said lead author Dr Sarah-Naomi James, from MRC Unit for Lifelong Health and Ageing at University College London.

"What's more, people who have never been active before, and then start to be active in their 60s, also appear to have better cognitive function than those who were never active," James added.

The second research, published in General Psychiatry, revealed that having unsatisfying social relationships can be as much of a risk factor for disease as obesity, physical inactivity or alcohol intake.

The findings led by a team from the University of Queensland in Australia showed that middle-aged women with the lowest levels of relationship satisfaction were more than twice as likely to develop multiple chronic conditions as those who were very satisfied with their relationships.

Although the study included only women, the findings still had "significant implications" for health, the researchers noted.