March 24, 2011
If you need another reason to quit smoking, here it is: People who are heavy smokers in middle age have nearly double the risk of developing Alzheimer’s disease in old age, a new study reports. Smoking, long known to be hazardous to the lungs and heart, also appears to be bad for the brain and memory as well.
The relationship between smoking and Alzheimer’s is complex. Some earlier reports suggested that the nicotine in cigarettes may be protective against neurologic ailments like Parkinson’s disease and help keep the memory sharp. But nobody recommends smoking, which is linked to lung cancer, stroke and heart attacks, to ward off Alzheimer’s or other brain diseases.
The study, published in the Archives of Internal Medicine, involved 21,123 men and women who were in their 50s and enrolled in a health plan in Finland from 1978 to 1985. All completed a medical and lifestyle survey initially, then were assessed again 20 years later, when they were in their 70s.
During that time, about a fourth of the participants had been given a diagnosis of Alzheimer’s or another form of dementia. Those who smoked more than two packs a day in middle age were at especially high risk. Former smokers or those who smoked less than half a pack per day, though, did not appear to be at increased risk. Men and women were equally at risk, as were those of different races.
The researchers, from the University of Eastern Finland and Kuopio University Hospital, noted that smoking is known to contribute to vascular disease and can damage blood vessels throughout the body, including the brain. Smoking also stokes inflammation, which is increasingly believed to be important in the development of Alzheimer’s disease. “It is possible that smoking affects the development of dementia via vascular and neurodegenerative pathways,” they note.
Early studies on smoking and Alzheimer’s risk were of shorter duration, lasting only two to seven years. “To our knowledge, this is the first study evaluating the amount of midlife smoking on long-term risk of dementia and dementia subtypes in a large multiethnic cohort,” the researchers said.
Alzheimer’s is increasingly being viewed as a disease that may take 10 to 20 years, or longer, to develop. So there is increased focus on finding measures that may stop the disease process early, before damage to the brain becomes extensive and irreversible.
“Our study suggests that heavy smoking in middle age increases the risk of both Alzheimer’s disease and vascular dementia for men and women across different race groups,” the authors concluded. “The large detrimental impact that smoking already has on public health has the potential to become even greater as the population worldwide ages and dementia prevalence increases.”
The findings add further support to the recommendation to stop smoking to help keep the mind sharp. Middle-aged smokers appear to have worse memories than their peers who don’t smoke, a 2008 study found [Read the article: “Middle-Age Smokers May Have Worse Memories Than Those Who Don’t Smoke“], and a poor memory at midlife increases the risk of Alzheimer’s in old age. Another study found that heavy smokers and drinkers got Alzheimer’s years earlier than those who don’t drink or smoke heavily. [Read the article, “Heavy Drinking, Smoking May Spur Onset of Alzheimer’s“] And a large European study of seniors 65 and older in 2004 found that older men and women who smoked showed greater decline in memory than those who had never smoked. [Read the article, “Smoking Is Bad for Your Brain, Too“]
Minna Rusanen; Miia Kivipelto; Charles P. Quesenberry; Jufen Zhou; Rachel A. Whitmer: Heavy Smoking in Midlife and Long-term Risk of Alzheimer Disease and Vascular Dementia. Archives of Internal Medicine, posted online doi:10.1001/archinternmed.2010.393 and scheduled for print, Feb. 28, 2011.