Association of blood cotinine level with cognitive and physical performance in non-smoking older adults

Abstract

Background Studies show that active smoking may be associated with cognitive decline. However, the consequence of secondhand smoke on cognitive and physical performance remains unclear. The purpose of this study was to assess the association of secondhand smoke with cognitive performance and physical function using a population-based sample. Methods Data of 2,542 non-smoking participants from the 1999–2002 National Health and Nutrition Examination Survey were analyzed. Secondhand smoke exposure level was estimated using blood cotinine concentrations. Cognitive performance was assessed with the Digit Symbol Substitution Test and self-reported confusion/memory problems. Physical performance was analyzed using visual gait speed (m/s) and self-reported physical function. Multivariate linear and logistic regression models were used to assess the association. Results In never smokers, cognitive performance score decreased by 2.03 points (95% confidence interval (CI): −3.00, −1.05) per one unit increase in log-transformed blood cotinine level. After adjusting for potential confounders, including diabetes, hypertension, body mass index, alcohol, and blood lead level, change in cognitive performance score was still statistically significant (−1.17 95% CI: −2.32, −0.02). Similar trends were observed in former smokers. Gait speed decreased by 0.02 m/s for one unit increase in log-transformed blood cotinine level. This was evident in both never and former smokers. The relationship remained significant after adjusting for potential confounders in former smokers. Conclusions Our study suggests that secondhand smoke may contribute to cognitive decline in never and former smokers. Considering the cross-sectional design and the limitations of this study, the relationship warrants further assessment.

Exposure to secondhand tobacco smoke and the frailty syndrome in US older adults

“…Among never smokers, high lifetime SHS exposure at home has been associated with decreased mineral density in both adult men and women (Holmberg et al 2011) and with increased risk of osteoporosis in postmenopausal women (Kim et al 2013b). Finally, in a crosssectional study based on NHANES 1999-2002, authors found that SHS exposure among nonsmoking older adults was associated with reduced physical function and reduced gait speed (Akhtar et al 2013). Interestingly, in our study, the association with reduced physical function and reduced gait speed was not statistically significant, suggesting that SHS-related frailty was mainly driven through the high frequency of weakness and exhaustion.…”

“…Department of Health and Human Services 2014). Some studies have also linked SHS exposure in older adults with the risk of dementia (Chen et al 2013a;Chen 2012;Barnes et al 2010), cognitive impairment (Chen et al 2013b;Akhtar et al 2013;Llewellyn et al 2009), and worse scores in the mental health dimension of the SF-36 (Mesquita et al 2015). Among never smokers, high lifetime SHS exposure at home has been associated with decreased mineral density in both adult men and women (Holmberg et al 2011) and with increased risk of osteoporosis in postmenopausal women (Kim et al 2013b).…”

Passive smoking as a risk factor for dementia and cognitive impairment: systematic review of observational studies

“…Nine papers were included in the final analysis, four of which reported research conducted in China (Chen, 2012 ; Chen et al , 2012 ; 2013a ; 2013b ), two in the UK (Llewellyn et al , 2009 ; Heffernan and O'Neill, 2013 ), two in the USA (Barnes et al , 2010 ; Akhtar et al , 2013 ), and one in Italy (Orsitto et al , 2012 ). They comprised seven cross-sectional studies, one between-groups design, and one longitudinal study.…”

“…Three studies also included clinical interview to verify diagnoses of dementia or the presence of cognitive impairment (Barnes et al , 2010 ; Chen, 2012 ; Orsitto et al , 2012 ). One paper included both a standardized test and self-reported functional limitation from memory impairment (Akhtar et al , 2013 ). Four studies (Barnes et al , 2010 ; Chen, 2012 ; Chen et al , 2012 ; 2013b ) referred to dementia as a measured outcome, one included both dementia and Mild Cognitive Impairment (Orsitto et al , 2012 ), another three focused on general cognitive impairment (Llewellyn et al , 2009 ; Akhtar et al , 2013 ; Chen et al , 2013a ), and one paper specifically examined prospective memory (Heffernan and O'Neill, 2013 ).…”

Cotinine impacts sensory processing in DBA/2 mice through changes in the conditioning amplitude

“…Two studies of the effects of second-hand smoke in non-smokers over 50 years of age, assessed serum cotinine levels as well as cognition. Both studies correlated higher levels of serum cotinine with poorer cognitive performance, even when scores were adjusted for comorbid complications such as diabetes or hypertension (Llewellyn et al 2009; Akhtar et al 2013). The present studies, which suggest potential improvement in a pre-attentional state, also suggest that there would not be overall improvement in inhibition, even if improvements in cognition were to be observed.…”