Study: Heavy Smoking in Midlife Hikes the Risk of Alzheimer’s

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Cigarette being put out in ashtray

As if anyone needed another reason for quitting: a new study found that heavy cigarette use in middle age more than doubles the risk of developing Alzheimer’s disease or dementia down the road.

The new study looked at data on more than 21,000 Kaiser Permanente Northern California members, ages 50 to 60, surveyed between 1978 and 1985. The researchers then tracked how many of those same people were diagnosed with dementia, including Alzheimer’s disease and vascular dementia, between 1994 and 2008 — when the subjects had reached an average age of 71.6 years. (More on Time.com: Video: Au Revoir Cigarettes)

A little more than 25% of the participants were diagnosed with some type of dementia in the follow-up. Heavy smokers — those who smoked more than two packs a day — were 157% more likely to develop Alzheimer’s disease than nonsmokers. And they were 172% more likely to be diagnosed with vascular dementia, the second most common form of dementia, than people who did not smoke.

Lighter smoking appeared to have later cognitive risks too: compared with nonsmokers, those who smoked a half-pack to one pack a day had a 37% higher risk of dementia, and those who smoked between one and two packs a day had a 44% greater risk. For the lightest smokers (less than a half-pack a day), however, there was no difference in risk compared with people who didn’t smoke. (More on Time.com: Study: Smoking During Pregnancy May Result in Uncoordinated Kids)

“It is possible that smoking affects the development of dementia via vascular and neurodegenerative pathways,” the study says. Similar to its role as a risk factor in stroke, smoking may affect dementia by damaging blood vessels and brain cells or increasing inflammation.

The study’s authors note that the link between smoking and dementia was constant across sex and race. The study was published online by the Archives of Internal Medicine.

More on Time.com:

Photos: My Aging Father’s Decline: A Son’s Photo Journal

Alzheimer’s: Largely a Woman’s Issue

The Impact of Alzheimer’s Disease by the (Very Scary) Numbers

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