Cognitive Function Affected by Early Adult to Midlife Smoking

LOS ANGELES — Using data from the Coronary Artery Risk Development in Young Adults (CARDIA), it has been shown that smoking in early adulthood to midlife is associated with midlife cognitive impairment, and that quitting smoking, even in midlife, can have cognitive benefits, this according to research presented at the Alzheimer’s Association International Conference 2019, held July 14 to 18, in Los Angeles, California.

Data included 3364 adults from the CARDIA study. Latent class analysis identified smoking trajectories based on assessments taken every 2 to 5 years from baseline (1985-1986) through year 25 (2010-2011). Cognitive outcomes at year 25 were based on scores from the Stroop test (inverse score), Rey Auditory Verbal Learning Test (RAVLT), and Digit Symbol Substitution Test (DSST). Logistic regression was used to examine associations between early to midlife smoking trajectories and cognitive impairment at midlife, defined as 1 standard deviation below the mean for each cognitive test.

Among the 3364 CARDIA participants with cognitive assessments (mean age 50.1 ±3.6 years, 56% women, 46% black), 49% reported ever smoking during the follow-up period. Subsequently, 5 smoking trajectories were identified: heavy declining smokers (n=86), heavy stable smokers (n=248), moderate stable smokers (n=334), minimal stable smokers (n=646), and quitters (n=324). When compared to never smoking, heavy stable smoking consistently predicted poor cognitive scores on all tests, even after adjusting for sex, age, race, income, education, diabetes, physical activity, hypertension, age of smoking initiation, depression, alcohol use, and marijuana use (DSST: full model adjusted odds ratio (AOR) 2.22; 95% CI, 1.53-3.22; Stroop test: AOR 1.58; 95% CI, 1.05-2.36; RAVLT: AOR 1.48; 95% CI, 1.05-2.10). Heavy declining smokers showed poor performance on the Stroop test and the DSST, and moderate stable smokers demonstrated poor performance on the DSST.

Minimal stable smokers and quitters showed no increased risk of cognitive impairment. Cumulative smoking for at least 10 pack-years was associated with poor cognitive scores on all tests (DSST: AOR, 1.87; 95% CI, 1.39-2.50; Stroop: AOR, 1.42; 95% CI, 1.04-1.93; RAVLT: AOR, 1.31; 95% CI, 1.00-1.70). 

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Study investigators concluded, “Early adult to mid-life smoking is associated with cognitive impairment at mid-life. These results underscore the risk of sustained heavy smoking from early to mid-life and the potential benefits of quitting on cognitive function, even in mid-life.”

Bahorik A. Early adult to mid-life cigarette smoking and cognitive function: findings from the Cardia study. Presented at: The Alzheimer’s Association International Conference; July 14-18, 2019; Los Angeles, CA. Abstract P3-572.