Childhood exposure to tobacco smoke and midlife cognitive performance: The Cardiovascular Risk in Young Finns Study

摘要

Background: Our previous study suggested a longitudinal association between smoking in adolescence/young adulthood and worse midlife learning and memory. Furthermore, previous studies have proposed cross-sectional and short-term negative associations between childhood exposure to tobacco smoke on cognitive performance, intelligence or academic achievements. However, the longitudinal association between childhood/adolescence exposure to tobacco smoke and midlife cognitive performance is unknown. Methods: From 1980, a population-based cohort of 3,596 children (baseline age 3-18 years) have been followed-up for 31 years in 3-9 year intervals. In 2011, cognitive testing was performed in 2,026 subjects aged 34-49 years using computerized test battery. The subjects were divided into two groups according to their cognitive performance: 1) low cognitive performance (lowest quartile of cognitive performance distribution) and 2) high cognitive performance (three highest quartiles of cognitive performance distribution). Regular and current smoking status was queried separately from both parents at baseline and the first follow-up study in 1983. Childhood fasting serum samples were collected in 1980 and cotinine levels were analysed. Parental smoking hygiene was determined using questionnaire data on parental smoking and the child's serum cotinine levels. The subjects were divided into: 1) no parental smoking (children with non-smoking parents and a serum cotinine level <3.0 ng/mL); 2) hygienic parental smoking (children with at least one smoking parent and a serum cotinine level <3.0 ng/mL); 3) non-hygienic parental smoking (children with at least one smoking parent and a serum cotinine level ≥3.0 and <20 ng/mL). Results: The subjects exposed to non-hygienic parental smoking in childhood/adolescence had worse midlife memory and learning compared to subjects with non-smoking parents (β = -0.26 SD, SE = 0.12; p = 0.03, adjusted for age, sex, childhood family socioeconomic status and adulthood smoking). The difference in midlife memory and learning between the exposed and non-exposed subjects corresponds to 5 years effect of aging. Childhood/adolescence exposure to non-hygienic parental smoking associated with increased risk of low midlife memory and learning (RR 1.64; 95% CI 1.04-2.57) and a borderline significant association was found for hygienic parental smoking (RR 1.30; 95% CI 0.95-1.80) compared to subjects with non-smoking parents even after taking into account several potential confounders. Additionally, a significant association was found between hygienic parental smoking and increased risk of low midlife short term and working memory (RR 1.48; 95% CI 1.08-2.03), while the association for non-hygienic parental smoking was borderline significant for that cognitive domain (RR 1.43; 95% CI 0.89-2.29). Conclusions: Exposure to tobacco smoke in childhood and adolescence may associate with worse learning and memory as well as poorer short term and working memory in midlife. Avoidance of exposure to tobacco smoke is important since childhood in order to promote adulthood cognitive performance.