Biomarker assessment of tobacco smoking exposure and risk of dementia death: pooling of individual-participant data from 14 cohort studies
journal contributionposted on 05.01.2018 by G. David Batty, Martin J. Shipely, Elisabeth Kvaavik, Tom C. Russ, Mark Hamer, Emmanuel Stamatakis, Mika Kivimaki
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Background: While there is a suggestion that self-reported tobacco smoking may be a risk factor for dementia, to date, it has not been possible to explore the thresholds at which this exposure elevates risk. Accordingly, our aim was to relate cotinine, a biomarker of tobacco smoking, to risk of dementia death. Methods: We pooled 14 prospective cohort studies that held data on cotinine (plasma or saliva), covariates, and death records. Results: In the 33,032 study members (17,107 women) with salivary cotinine data, a mean duration of 8.3 years of follow-up gave rise to 135 deaths ascribed to dementia; while in 15,130 study members (7995 women) with plasma cotinine data, there were 119 dementia deaths during 14.3 years of mortality surveillance. After multiple adjustment, both plasma cotinine (hazard ratio per one standard deviation higher cotinine; 95% confidence interval: 1.29; 1.05, 1.59) and salivary cotinine (1.10; 0.89, 1.36) were positively related to dementia risk, with stronger effects for plasma. Conclusion: Our finding that plasma cotinine was related to an elevated risk of dementia death warrants testing in studies with measures of disease onset as opposed to just mortality.
GDB is supported by the UK Medical Research Council (MRC) and the US National Institute on Aging; MS by the British Heart Foundation; MK by the UK MRC, NordForsk, and the Nordic Research Programme on Health and Welfare; and ES by a National Health and Medical Research Council (Australia) Senior Research Fellowship.
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