Smoking might cause an increased risk for poor memory in middle-aged adults, according to a meta-analysis published in the June 9 Archives of Internal Medicine. The study, which was conducted by Séverine Sabia, MSc, of the Institut National de la Santé et de la Recherche Médicale, Villejuif, France, and colleagues, determined that smoking is a risk factor for dementia.
Ms. Sabia and her team analyzed data from 10,308 London-based civil servants ages 35 to 55 who enrolled in the Whitehall II study between 1985 and 1988 (phase 1). Smoking habits were assessed initially and again during 1997 to 1999 (phase 5). A total of 5,388 participants were available to complete memory, reasoning, vocabulary, and verbal fluency tests in phase 5, and 4,659 were retested five years later.
Phase 1 smokers had a higher risk of death (hazard ratio, 2.00) and of nonparticipation in cognitive tests (odds ratio, 1.32) during the average 17 years of follow-up, compared with never smokers. At phase 5, smokers were more likely than never smokers to be in the lowest-performing group (ie, the lowest 20%).
The participants who were ex-smokers at phase 1 of the study were 30% less likely than current smokers to have poor vocabulary and low verbal frequency scores. Those who stopped smoking during the study experienced more improvement in other health habits, such as drinking less alcohol, eating more fruits and vegetables, and becoming more physically active.
The researchers noted four key findings of the study. “First, smoking in middle age is associated with memory deficit and decline in reasoning abilities. Second, long-term ex-smokers are less likely to have cognitive deficits in memory, vocabulary, and verbal fluency. Third, giving up smoking in midlife is accompanied by improvement in other health behaviors. Fourth, our results based on a large prospective cohort study of middle-aged British civil servants suggests that the association between smoking and cognition, even in late midlife, could be underestimated because of higher risk of death and nonparticipation in cognitive tests among smokers,” they said.
The study’s findings are important because individuals with cognitive impairment in midlife may progress to dementia at a faster rate, according to the authors. “During the past 20 years, public health messages about smoking have led to changes in smoking behavior, … [and they] should continue to target smokers of all ages,” Ms. Sabia and colleagues concluded.