Can smoking cause Alzheimer's disease?

Anthony Cirillo
Geriatric Medicine
While smoking does not necessarily cause Alzheimer's disease, smoking does double the risk of Alzheimer's.

A Kaiser Permanente study reported that an analysis of more than 20,000 men and women, studied since 1978, found a 157% heightened risk of Alzheimer's for people who smoked two packs or more a day.

Some believe the numbers may still be an underestimation. Kenneth Hepburn, an associate dean for research at the Emory University School of Nursing, told CNN that many smokers may die before they develop Alzheimer's disease or dementia, and therefore not show up in data collected.

Researchers are unsure of why the association between smoking and Alzheimer's is so strong. Rachel Whitmer, the study's co-author said that smoking may play a role in the damage of blood vessels, as well as brain cells.
Smoking is a risk factor for cardiovascular disease, so it makes sense that it would also make you vulnerable to Alzheimer's disease and other dementias. A review pooling results from 19 different studies estimated that elderly smokers faced a nearly 80% higher risk of Alzheimer's disease than those who had never smoked.

However, it is unclear how much quitting smoking reduces your risk of Alzheimer's. At least one study found inconsistent links between smoking history and cognitive decline, perhaps due to the difficulty of tracking and testing former smokers. Another -- a study in Archives of Internal Medicine -- found that among a sample of over 21,000 people, those who smoked more than two packs of cigarettes a day at midlife had more than double the risk of developing dementia in old age when compared with nonsmokers. However, people who had stopped smoking by midlife and those who smoked less than half a pack a day had a risk of dementia similar to that of people who had never smoked.

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