Seniors who smoke are significantly more likely to develop forms of dementia or Alzheimer’s disease than those who don’t, or those who quit in the past, Dutch researchers say.

There is a 50% increase in likelihood of Alzheimer’s for older smokers, they concluded. Researchers studied 7,000 individuals 55 and older over a seven-year period to compile their findings.

“Smoking increases the risk of cerebrovascular disease, which is also tied to dementia,” said study author Monique Breteler, MD, PhD, of Erasmus Medical Center in Rotterdam. Her study is published in the Tuesday’s issue of Neurology, the medical journal of the American Academy of Neurology.

Breteler said oxidative stress, which can damage blood-vessel cells and lead to hardening of the arteries, also could be a factor. Oxidative stress is more prevalent in both smokers and those who have Alzheimer’s.