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

Effect of smoking on physical and cognitive capability in later life: a multicohort study using observational and genetic approaches
Effect of smoking on physical and cognitive capability in later life: a multicohort study using observational and genetic approaches
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.
1-13
North, T.L.
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Palmer, T.M.
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Lewis, S.J.
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Cooper, R.
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Power, C.
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Pattie, A.
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Starr, J.M.
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Deary, I.J.
e3403cfe-eb5b-4941-903d-87ef0db89c60
Martin, R.M.
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Aihie Sayer, A.
fb4c2053-6d51-4fc1-9489-c3cb431b0ffb
Kumari, M.
b5ac445e-8cbd-4f37-a99e-630bf0e9b600
Cooper, C.
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Kivimaki, M.
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Kuh, D.
6c5d95a4-433d-4895-bd95-86a7d5fe76a5
Ben-Shlomo, Y.
920afa6a-6f07-48ff-a238-24fd5cdd1638
Day, I.N.
e9cacaf7-f4c8-4ef0-82fa-b459ad683d50
North, T.L.
46e30b89-6bed-497d-bdc2-bca41da276da
Palmer, T.M.
fb4b7b18-4328-49fa-bb14-1c5bb7feb13b
Lewis, S.J.
79610fec-3a6c-4da5-88e6-0f5b45583650
Cooper, R.
6cd7b578-a1fa-4511-bc7d-9addc4baf372
Power, C.
00309de2-e4ca-4b1a-a073-152c31be3f46
Pattie, A.
f9b29f26-b88d-4c18-bdf6-8ef74781a5a5
Starr, J.M.
efba1461-fa5a-4669-9801-d6530f48d01c
Deary, I.J.
e3403cfe-eb5b-4941-903d-87ef0db89c60
Martin, R.M.
fe0378e6-5c70-4361-b909-3b459cdf2181
Aihie Sayer, A.
fb4c2053-6d51-4fc1-9489-c3cb431b0ffb
Kumari, M.
b5ac445e-8cbd-4f37-a99e-630bf0e9b600
Cooper, C.
e05f5612-b493-4273-9b71-9e0ce32bdad6
Kivimaki, M.
87a6c408-c8b5-48dc-b2c0-e1f425b91dc6
Kuh, D.
6c5d95a4-433d-4895-bd95-86a7d5fe76a5
Ben-Shlomo, Y.
920afa6a-6f07-48ff-a238-24fd5cdd1638
Day, I.N.
e9cacaf7-f4c8-4ef0-82fa-b459ad683d50

North, T.L., Palmer, T.M., Lewis, S.J., Cooper, R., Power, C., Pattie, A., Starr, J.M., Deary, I.J., Martin, R.M., Aihie Sayer, A., Kumari, M., Cooper, C., Kivimaki, M., Kuh, D., Ben-Shlomo, Y. and Day, I.N. (2015) Effect of smoking on physical and cognitive capability in later life: a multicohort study using observational and genetic approaches. BMJ Open, 5 (12), 1-13. (doi:10.1136/bmjopen-2015-008393). (PMID:26671949)

Record type: Article

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.

Full text not available from this repository.

More information

Accepted/In Press date: 29 October 2015
e-pub ahead of print date: 15 December 2015
Published date: 15 December 2015
Organisations: Faculty of Medicine

Identifiers

Local EPrints ID: 385216
URI: http://eprints.soton.ac.uk/id/eprint/385216
PURE UUID: b42ee58d-aca1-4eee-9135-a37dfa958539
ORCID for C. Cooper: ORCID iD orcid.org/0000-0003-3510-0709

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Date deposited: 18 Jan 2016 12:09
Last modified: 03 Dec 2019 01:58

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Contributors

Author: T.L. North
Author: T.M. Palmer
Author: S.J. Lewis
Author: R. Cooper
Author: C. Power
Author: A. Pattie
Author: J.M. Starr
Author: I.J. Deary
Author: R.M. Martin
Author: A. Aihie Sayer
Author: M. Kumari
Author: C. Cooper ORCID iD
Author: M. Kivimaki
Author: D. Kuh
Author: Y. Ben-Shlomo
Author: I.N. Day

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