Childhood exposure to parental smoking and midlife cognitive function: The Young Finns Study

We studied whether exposure to parental smoking in childhood/adolescence is associated with midlife cognitive function, leveraging data from the Cardiovascular Risk in Young Finns Study. A population-based cohort of 3,596 children/adolescents aged 3-18 years was followed between 1980 and 2011. In 2011, cognitive testing was performed on 2,026 participants aged 34-49 years using computerized testing. Measures of secondhand smoke exposure in childhood/adolescence consisted of parental self-reports of smoking and participants' serum cotinine levels. Participants were classified into 3 exposure groups: 1) no exposure (nonsmoking parents, cotinine <1.0 ng/mL); 2) hygienic parental smoking (1-2 smoking parents, cotinine <1.0 ng/mL); and 3) nonhygienic parental smoking (1-2 smoking parents, cotinine ≥1.0 ng/mL). Analyses adjusted for sex, age, family socioeconomic status, polygenic risk score for cognitive function, adolescent/adult smoking, blood pressure, and serum total cholesterol level. Compared with the nonexposed, participants exposed to nonhygienic parental smoking were at higher risk of poor (lowest quartile) midlife episodic memory and associative learning (relative risk (RR) = 1.38, 95% confidence interval (CI): 1.08, 1.75), and a weak association was found for short-term and spatial working memory (RR = 1.25, 95% CI: 0.98, 1.58). Associations for those exposed to hygienic parental smoking were nonsignificant (episodic memory and associative learning: RR = 1.19, 95% CI: 0.92, 1.54; short-term and spatial working memory: RR = 1.10, 95% CI: 0.85, 1.34). We conclude that avoiding childhood/adolescence secondhand smoke exposure promotes adulthood cognitive function.