July 9, 2008
Need another reason to quit smoking? Middle-aged smokers appear to have worse memories than their peers who don't smoke. And a poor memory at midlife increases the risk of Alzheimer's disease and other forms of dementia in old age.
The findings highlight the important connection between smoking and brain health. In numerous reports, smoking has emerged as a risk factor for dementia. The current findings add more fuel to the fire about the dangers of smoking for all the cells in the body, including those critical for thinking and memory in the brain. The study was published in the Archives of Internal Medicine, a journal from the American Medical Association.
Researchers in France analyzed data from 10,308 civil servants working in London between 1985 and 1988. They ranged in age from 35 to 55 and were part of an ongoing study called Whitehall II. Researchers asked whether they smoked during those years, and again more than 10 years later, from 1997 to 1999. Almost half the study participants were given tests to assess memory, reasoning, vocabulary and verbal fluency during those later years. Most were re-tested for memory and thinking five years later.
The authors of the study noted that their results led to four key findings about the link between smoking in midlife and memory decline.
First, smoking in middle age was associated with memory problems and a decline in reasoning abilities. At the first round of cognitive testing, from 1997 to 1999, those who smoked were more likely to be in the lowest-performing group (bottom 20 percent) in terms of memory compared with those who had never smoked.
Second, people who had given up smoking years earlier were less likely to have memory problems or problems related to vocabulary or verbal fluency. Those who reported being ex-smokers at the beginning of the study were 30 percent less likely than smokers to have poor vocabulary and low verbal frequency scores.
Third, giving up smoking led to lifestyle improvements that may help to keep memory sharp into old age. Individuals who stopped smoking during the study also experienced more improvement in other health habits, like drinking less alcohol, being more physically active and eating more fruits and vegetables. Studies suggest that all those activities are important for lowering the risk of Alzheimer's disease.
Finally, the researchers concluded that the negative effects of smoking on cognition, even in late midlife, were probably underestimated. That's because men and women who smoked at the beginning of the study were more likely to die from various causes during the average 17 years of follow-up. They were also less likely to participate in the cognitive testing.
The results are important because individuals with poor memories in midlife may progress to dementia at a faster rate, the authors note. "During the past 20 years, public health messages about smoking have led to changes in smoking behavior," they write. "Public health messages on smoking should continue to target smokers of all ages."
The findings underline the importance of quitting smoking at any age. And it is likely that the younger you quit, the better. Smoking contains numerous noxious chemicals that harm blood vessels throughout the body, including the brain. And poor blood flow to the brain may lead to memory loss and, in later years, dementia.
The findings are consistent with earlier researcher showing smoking is bad for the brain. A large European study of seniors 65 and older in 2004, for example, found that older men and women who smoked showed greater decline in memory than those who had never smoked. [See the article, "Smoking Is Bad for Your Brain, Too"] And a recent report found that heavy smokers and drinkers got Alzheimer's years earlier than those who don't drink or smoke heavily. [See the article, "Heavy Drinking, Smoking May Spur Onset of Alzheimer's"]
Severine Sabia, MSc; Michael Marmot, PhD; Carole Fufouil, PhD, Archana Singh-Manoux, PhD: "Smoking History and Cognitive Function in Middle Age From the Whitehall II Study." Archives of Internal Medicine, Volume 168 (Number 11): June 9, 2008, pages 1165-1173.