The risk of dementia is 40% for lonely people, according to a new study.
Scientists have yet to determine the association between loneliness and memory disorders.
They believe it may be that social isolation may trigger inflammation in the brain or increase a person's risk of having an unhealthy lifestyle, the Daily Mail reported.
While the direct cause of dementia is still unclear, diet and exercise has been found to reduce the risk of developing the condition.
For the study, data of close to 12,030 people over 50 revealed how lonely and socially isolated they felt.
"It's a feeling that you do not fit in or do not belong with the people around you," lead author Dr Angelina Sutin from Florida State University, told the Daily Mail.
Adding," You can have somebody who lives alone, who doesn't have very much contact with people, but has enough - and that fills their internal need for socialising.
"So even though objectively you might think that person is socially isolated, they don't feel lonely.
"The flip side is that you can be around a lot of people and be socially engaged and interactive and still feel like you don't belong."
1,104 of the participants developed dementia during the study.
Results showed loneliness significantly increased a person's risk of dementia, regardless of age or gender.
The findings were originally published in the Journal of Gerontology: Psychological
