People exposed to second-hand smoke may face nearly 44% increased risk of developing dementia. Smoking is already known to increase the risk for dementia and Alzheimer’s disease.

A study from Peninsula Medical School in Exeter, England, published in the British Medical Journal, has shown an association between cognitive function and exposure to passive smoking. The risk increases with the amount of exposure to second-hand smoke. For people at the highest levels of exposure, the risk is probably higher.

The study collected data on over 4,800 nonsmokers who were over 50 years old and tested the saliva samples from these people for levels of cotinine, a product of nicotine found in saliva for about 25 hours following exposure to smoke. Investigators noted that the individuals with the highest cotinine levels had a 44% increased risk of cognitive impairment, when compared with those with the lowest cotinine levels. Although the risk of impairment was lower in people with lower cotinine levels, it was still significant.

Passive smoking is also linked with an increased risk of stroke and heart disease.