Higher blood cotinine level is associated with worse cognitive functioning in non-smoking older adults

Abstract

IntroductionSecondhand smoke (SHS) is common in older adults; however, its cognitive effect is unclear. We aimed to examine the association between serum cotinine level and cognitive functioning among non-smoking older adults.Materials and methodsA total of 2,703 older adults aged 60 and above from the National Health and Nutrition Examination (NHANES) Survey 2011–2014 were included. Serum cotinine level was analyzed in the laboratory. A level ≤10 ng/ml and a response of “no” to the question “Do you currently smoke?” were used to select non-smokers. Cognitive functioning was measured using the Consortium to Establish a Registry for Alzheimer’s disease Word Learning subtest (CERAD-WL) immediate and delayed recall tests, the Animal Fluency test (AFT), and the Digit Symbol Substitution test (DSST). Multivariable linear regression models were constructed to examine the association between serum cotinine level quartile and test-specific and global cognition z scores adjusting for age, race/ethnicity, education, depressive symptoms, body mass index, alcohol use, smoking history, prevalent coronary heart disease (CHD), stroke, and systolic blood pressure.ResultsAbout half of the participants (mean age 70.5 years) were female (53.6%), non-Hispanic White (48.3%), and completed some college and above (50.2%). Multivariate linear regressions with a reference group being those in the 1st quantile (lowest) showed that participants in the 4th quartile (highest) of serum cotinine level had lower immediate recall [β = −0.16, 95% confidence interval (CI) = −0.29, −0.03], AFT (β = −0.19, 95% CI = −0.33, −0.05), DSST (β = −0.27, 95% CI = −0.39, −0.15), and global cognition (β = −0.26, 95% CI = −0.39, −0.14) z scores. Participants in the 3rd quartile had lower immediate recall (β = −0.16, 95% CI = −0.30, −0.02) and global cognition (β = −0.16, 95% CI = −0.29, −0.02) z scores. Participants in the 2nd quartile had lower delayed recall z scores (β = −0.16, 95% CI = −0.29, −0.02).ConclusionHigher serum cotinine level was associated with worse cognitive functioning in non-smoking older adults. Prevention and reduction of SHS in older adults may help protect their cognitive functioning.

Concurrent serum lead levels and cognitive function in older adults

“…In the present study, we categorized participants' plasma levels of lead into four groups based on quartile and used the 1st quartile (the lowest quartile) as a reference. This is consistent with prior NHANES-based epidemiological studies (Fu et al, 2022a , b ; Li et al, 2023 ).…”

“…To minimize potential confounding between plasma lead levels and cognitive function, we reviewed the literature (Ge et al, 2018 , 2020 ; Li et al, 2019 ; Fu et al, 2022a ) and adjusted for covariates, including age (years), sex (male or female), race/ethnicity (Mexican Americans, other Hispanics, non-Hispanic white, or non-Hispanic Black), an education level (below high school, high school graduate, or some college or above), depressive symptoms, body mass index (kg/m 2 ) (< 18.5, 18.5-24.9, 25-29.9, or ≥30), and alcohol use (drinks per day) (0–1, 2, or 3 and more). Depressive symptoms were measured using the Patient Health Questionnaire, whose total score ranges between 0 and 27.…”

Frailty is associated with worse cognitive functioning in older adults

“…To control for confounding between frailty status and cognitive functioning, we reviewed the literature ( 8 , 9 , 32 ) and the following covariates were included in the analysis- age (years), sex (male or female), race/ethnicity (Mexican Americans, other Hispanics, non-Hispanic White, or non-Hispanic Black), education (below high school, high school graduate, or some college or above), total cholesterol (mg/dL), and systolic blood pressure (mmHg).…”

Nicotine exposure and mild cognitive impairment in the elderly：A mixtures approach

“…However, reducing smoking was associated with an increased risk of dementia, suggesting that lowering smoking in a smoking population still has an impairment in cognitive function. [4] The above findings were also found in multiple cohort populations [5,6] .Low-level exposure to nicotine alone has been found to cause neurodevelopmental damage in infants and children exposed to second-hand smoke. [7] The results on the effects of tobacco exposure on cognitive function are more divergent, with factors such as the amount of tobacco smoked [8], gender [9], and APOE genotype [10,11] influencing the association between tobacco exposure and cognitive function.…”