People who smoke may have an increased risk of developing dementia compared to non-smokers and those who quit the habit a long time ago, the results of a new study have found.

Researchers in Korea looked at over 46,000 men aged 60 years or older, who had taken part in a health screening programme between 2002 and 2013.

They found that those who had never smoked had a 19% reduced risk of developing dementia compared to continual smokers. Long-term quitters had a 14% reduced risk.

When it came to Alzheimer's disease, which is the most common type of dementia, people who had never smoked had an 18% reduced risk of developing the condition compared to continual smokers.

The study also found that long-term quitters had a 32% reduced risk of developing vascular dementia, which is the second most common type of dementia, compared with continual smokers. People who had never smoked had a 29% reduced risk.

"Smoking cessation was clearly linked with a reduced dementia risk in the long term, indicating that smokers should be encouraged to quit in order to benefit from this decreased risk," said the study's senior author, Dr Sang Min Park, of Seoul National University.

Details of these findings are published in the journal, Annals of Clinical and Translational Neurology.