WASHINGTON (Reuters) - People who smoke are more likely to develop Alzheimer's disease and other forms of dementia than people who have quit or have never smoked, Dutch researchers reported on Sunday.
Smokers over the age of 55 were 50 percent more likely to develop dementia than similar nonsmokers, Dr. Monique Breteler of Erasmus Medical Center in Rotterdam, Netherlands, and colleagues found.
Writing in the journal Neurology, Breteler and colleagues said they followed nearly 7,000 people age 55 and older for an average of seven years.
Over that time, 706 of the people developed dementia.
There is a well-known gene that raises the risk of dementia called APOE4 or apolipoprotein E4.
Smoking did not affect the Alzheimer's risk for people who had that gene. But people who did not have the gene had a 70 percent higher risk of Alzheimer's if they smoked.
Smoking could cause small strokes, which in turn damage the brain and cause dementia, Breteler said.
"Smoking increases the risk of cerebrovascular disease (stroke), which is also tied to dementia," Breteler said in a statement.
"Another mechanism could be through oxidative stress, which can damage cells in the blood vessels and lead to hardening of the arteries. Smokers experience greater oxidative stress than nonsmokers, and increased oxidative stress is also seen in Alzheimer's disease."
Oxidative stress is a process akin to rusting, in which chemical reactions damage the DNA.
