Research Repository

Effect of smoking on physical and cognitive capability in later life: A multicohort study using observational and genetic approaches

North, TL and Palmer, TM and Lewis, SJ and Cooper, R and Power, C and Pattie, A and Starr, JM and Deary, IJ and Martin, RM and Sayer, AA and Kumari, M and Cooper, C and Kivimaki, M and Kuh, D and Ben-Shlomo, Y and Day, INM (2015) 'Effect of smoking on physical and cognitive capability in later life: A multicohort study using observational and genetic approaches.' BMJ Open, 5 (12). ISSN 2044-6055

[img]
Preview
Text
BMJ Open-2015-North-.pdf - Published Version
Available under License Creative Commons Attribution.

Download (1MB) | Preview

Abstract

Objectives: The observed associations between smoking and functional measures at older ages are vulnerable to bias and confounding. Mendelian randomisation (MR) uses genotype as an instrumental variable to estimate unconfounded causal associations. We conducted a meta-analysis of the observational associations and implemented an MR approach using the smoking-related single nucleotide polymorphism rs16969968 to explore their causal nature. Setting: 9 British cohorts belonging to the HALCyon collaboration. Participants: Individual participant data on N=26 692 individuals of European ancestry (N from earliest phase analysed per study) of mean ages 50-79 years were available for inclusion in observational meta-analyses of the primary outcomes. Primary outcomes: Physical capability, cognitive capability and cognitive decline. The smoking exposures were cigarettes per day, current versus ex-smoker, current versus never smoker and ever versus never smoker. Results: In observational analyses current and ever smoking were generally associated with poorer physical and cognitive capability. For example, current smokers had a general fluid cognition score which was 0.17 z-score units (95% CI -0.221 to -0.124) lower than ex-smokers in cross-sectional analyses. Current smokers had a walk speed which was 0.25 z-score units lower than never smokers (95% CI -0.338 to -0.170). An MR instrumental variable approach for current versus ex-smoker and number of cigarettes smoked per day produced CIs which neither confirmed nor refuted the observational estimates. The number of genetic associations stratified by smoking status were consistent with type I error. Conclusions: Our observational analysis supports the hypothesis that smoking is detrimental to physical and cognitive capability. Further studies are needed for a suitably powered MR approach.

Item Type: Article
Subjects: R Medicine > R Medicine (General)
Divisions: Faculty of Social Sciences > Institute for Social and Economic Research
Depositing User: Jim Jamieson
Date Deposited: 25 Feb 2016 15:18
Last Modified: 17 Aug 2017 17:28
URI: http://repository.essex.ac.uk/id/eprint/16132

Actions (login required)

View Item View Item