Living with a smoker is not only bad for your health, it can also cause you to lose your memory, according to new research.
Experts have discovered that non-smokers who share a house with or spend time with smokers are likely to become forgetful as the second-hand smoke damages their memory.
The findings, published in the journal Addiction, show that non-smokers who are in regular contact with smokers forget 20% more than non-smokers who have none or little exposure to second-hand smoke.
And the results show that smokers risk the biggest memory loss of all, recalling 30% less than those who are not exposed to second-hand smoking.
For the study, which is the first to explore the relationship between other people's smoke and daily memory problems, researchers at the Collaboration for Drug and Alcohol Research Group at Northumbria University in the UK divided participants up into three different groups.
They compared a group of current smokers with two groups of non-smokers - one which was comprised of people who were regularly exposed to second-hand smoke and the other which was not.
The researchers discovered that non-smokers who had been exposed to second-hand smoke forgot almost 20 per cent more in the memory tests that those non-smokers not exposed.
However, both groups out-performed the current smokers who forgot 30 per cent more than those who were not exposed to second-hand smoking.
Dr. Tony Heffernan, lead researcher, said: "According to recent reports by the World Health Organisation, exposure to second-hand smoke can have serious consequences on the health of people who have never smoked themselves, but who are exposed to other people's tobacco smoke.
"Our findings suggest that the deficits associated with second-hand smoke exposure extend to everyday cognitive function.
"We hope our work will stimulate further research in the field in order to gain a better understanding of the links between exposure to second-hand smoke, health problems and everyday cognitive function."
Although 29 per cent of people in Ireland smoke, health experts say those who quit feel the benefits immediately.
Stopping smoking before the age of 35 gives you a similar life expectancy to a lifelong non-smoker, while packing the habit in before the age of 50 reduces your risk of dying in the next 15 years by half.