Passive smoking has been linked to an increased risk of a number of different health problems and now a study is suggesting that it could be linked to dementia. The study looked at 5,000 adults over the age of 50. Saliva samples were taken to measure the levels of a substance called cotinine, a product of nicotine found in saliva for around a day after exposure to second-hand smoke. The participants were also given tests aimed at measuring their brain performance, such as verbal memory and keeping track of time. The study found a 44% increased risk of dementia and other forms of cognitive problems for people exposed to high levels of second-hand smoke. One possible explanation is that passive smoking increase the risk of heart disease and stroke, conditions known to increase the risk of dementia and other cognitive problems.