Divorcees, widowers and middle-aged people who live alone are much more likely to develop dementia than those who are married or who live together, researchers say.
The findings, from a Swedish team and published online by the British Medical Journal, suggest that being in a steady relationship helps insulate people against mental decline, while singletons and those who lack regular social contact are at greater risk of developing a brain-wasting condition such as Alzheimer's.
People who either do not have a partner in their middle years, or whose partner dies, are three times more likely to end up with dementia than those who are married or cohabiting, the researchers find.
People of the same age who live alone have twice the risk of developing dementia, claim researchers.
The team, led by Miia Kivipelto, from the Karolinska Institutet medical university, Sweden, says the results add to evidence suggesting that social interaction plays a key role in sustaining heathy brain function into later life. "Living in a relationship with a partner might imply cognitive and social challenges that have a protective effect against cognitive impairment in later life."
Previous research has identified physical activity, education, mentally demanding work, working in higher managerial positions and certain hobbies, as factors that help ward off dementia. Some studies have found that friendships and a busy social life also reduce the risk.
About 700,000 people in the UK have some form of dementia, and that figure is expected to rise to 1.7 million by 2051. There is a trend towards one-person households, with 7.25 million people now living alone, says the Office for National Statistics. The researchers studied 2,000 men and women from eastern Finland, who took part in a study of cardiovascular risk factors, ageing and dementia, when they were about 50 and then again about 21 years later. While both single men and women had a "significant" extra risk of dementia, men had a "slightly higher odds ratio", the researchers said.
